international plant resistance to insects (ipri ...scentsoc.org/volumes/jaue/26/263107.pdf ·...

International Plant Resistance to Insects (IPRI),Nineteenth Biennial Workshop, 28–31 March 2010,

Charleston, SC1

Michael J. Stout,2 D. Michael Jackson,3 Louis S. Hesler,4 Marion O. Harris,5

Lee French,6 Nora L. V. Lapitan,7 James A. Reinert,8 Anna-Maria Botha-Oberholster9

IPRI Steering Committee (2008–2010)

J. Agric. Urban Entomol. 26(3): 107–134 (July 2009)

ABSTRACT The Nineteenth Biennial Meeting of the International PlantResistance to Insects (IPRI) Workshop was held 28–31 March 2010 inCharleston, SC. This workshop was attended by 71 participants from sixcountries. There were 17 symposium papers (three symposia), 22 submittedpapers, 9 student competition papers, and 21 posters presented. The abstractsof 52 of the 69 presentations and posters are presented herein.

KEY WORDS IPRI, host plant resistance, plant resistance to insects

The Nineteenth Biennial Meeting of the International Plant Resistance toInsects (IPRI) Workshop was held 28–31 March 2010 at the USDA-ARS, U.S.Vegetable Laboratory (USVL) and at the Hampton Inn and Suites West Ashley,Charleston, SC. Co-chairs for the workshop were Michael J. Stout (LouisianaState University, Baton Rouge, LA) who organized the program, and D. MichaelJackson (USDA-ARS, Charleston, SC) who handled local arrangements. Themeeting began with registration and a welcome mixer on Sunday evening. Acatered banquet and business meeting were held on Monday evening. Richard L.Fery (Research Leader, USDA-ARS, Charleston, SC) provided the invitedpresentation at the IPRI banquet: ‘‘Host plant resistance to diseases and pests:USDA efforts to develop improved cultivars of vegetable crops for use in thesoutheastern United States.’’ Dr. John Reese was honored at the banquet with aplaque of recognition for his many years of service to IPRI. The two new Steering

1Accepted for publication 27 September 2010.2 Department of Entomology, 404 Life Sciences Building, Louisiana State University Baton Rouge, LA,

70803.3 USDA-ARS, U.S. Vegetable Laboratory, 2700 Savannah Highway, Charleston, SC, 29414.4 USDA-ARS, North Central Agricultural Research Laboratory, 2923 Medary Avenue, Brookings, SD,

57006.5 Department of Entomology, North Dakota State University, 270 Hultz Hall, NDSU Dept. 7650, P.O.

Box 6050, Fargo, ND, 58108.6 Lee French Agricultural Research, Inc., RR# 2, Box 294, Lamberton, MN, 56152.7 Department of Soil and Crop Sciences, C119 Plant Science Building, Colorado State University, Ft.

Collins, CO, 80523.8 Department of Entomology, 412 Minnie Belle, Heep Bldg., Texas A&M University, 2475 TAMU,

College Station, TX, 77843.9 Department of Genetics, Stellenbosch University, Private Bag X1, Matieland 7601, South Africa.

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Committee members elected for 2010–2016 were Dolores Mornhinweg andRichard Musser. Monetary awards were presented at the banquet to winners ofthe student paper competition. On Tuesday afternoon (30 March 2010), the grouptook a field trip to the Angel Oak Tree on Johns Island and to the Irvin-HouseVineyards & Firefly Distillery on Wadmalaw Island, SC. That evening, areception and dinner were held at Gilligan’s Island Porch Restaurant. Thisworkshop was attended by 71 participants from six countries. There were 17symposium papers (in three symposia), 22 submitted oral presentations (in foursessions), nine student-competition papers, and 21 submitted posters that weredisplayed in the meeting room for the duration of the workshop. The authors of 52of the 69 presentations and posters agreed to publish their abstracts herein. Thenext biennial IPRI Workshop will be held in 2012, with Marion Harris, LeeFrench, and Louis Hesler forming the organizing committee. IPRI has met everyother year since the first meeting in 1974 at Indianapolis, IN. For moreinformation, visit the IPRI website at http://www.k-state.edu/ipri/.

ABSTRACTS

Symposium: The interactions of plant resistance and natural enemies:Implications for agriculture. Michael J. Stout, Moderator

Interaction between host plant resistance and biological control ofthe soybean aphid. Kelley J. Tilmon (South Dakota State University,Brookings, SD), N. Seiter, C. Krupke, M. Kates, C. DiFonzo, T. Heidel, D.Ragsdale, D. Prischmann, B. McCornack & D. Hogg. Host plant resistance andbiological control are two cornerstones of integrated pest management. Butintegrating these tools with each other requires an understanding of how theyinteract, not just how they function individually. Biological control and host plantresistance have both been shown to provide significant population suppression ofsoybean aphid (Aphis glycines), a major pest of soybean (Glycine max). Thepurpose of this study was to determine the impact of natural enemies on soybeanaphid population growth on aphid-resistant soybeans [Rag1 gene] relative tosusceptible soybeans, under field conditions. This was a multistate study withcoordinated trials in IN, MI, MN, ND, SD, and WI. Preliminary analyses suggestthat in this study there was an interaction between host plant resistance andbiological control. Though aphid populations were lower overall in resistantsoybeans, natural enemies had a proportionally greater effect in susceptiblesoybeans. These results and their implications for soybean IPM will be discussed.

Potential for nematode-induced fitness costs to delay pest resistanceto Bt crops. Aaron J. Gassmann (Iowa State University, Ames, IA). The pastdecade has witnessed a rapid increase in the use of crops genetically modified toproduce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). Thispresents the challenge of designing agricultural systems to manage pests and theevolution of resistance to Bt. Currently, the refuge strategy is used in the UnitedStates and elsewhere to delay pest resistance, and requires planting of non-Bthost plants near a Bt crop. I will discuss research that tests whetherincorporation of entomopathogenic nematodes into refuges might act to prolongthe efficacy of Bt crops by increasing the fitness cost of Bt resistance. Fitnesscosts occur when, in the absence of Bt toxin, resistant insects are less fit than

108 J. Agric. Urban Entomol. Vol. 26, No. 3 (2009)

susceptible insects. Laboratory assays reveal the some species of entomopatho-genic nematodes increase the fitness cost of Bt resistance, indicating that theirpresence in refuges may delay Bt resistance; a conclusion that is furthersupported by the results of simulation modeling. This research points to the valueof developing integrated pest management strategies for Bt crops that includesincorporation of entomopathogenic nematodes into non-Bt refuges.

Lose a little, gain a lot: Aphids can benefit cotton plants throughinduced defenses and apparent competition. Adrianna Szczepaniec (TexasA&M University, College Station, TX), R. Ramirez & M. D. Eubanks. Indirectinteractions between herbivores may affect natural enemies and plant defensesinvolved in the control of herbivores. Here we show how a less damagingherbivore, Aphis gossypii, influences plant defense traits and foraging of anatural enemy that affect subsequent herbivory by a chewing herbivore, the beetarmyworm Spodoptera exigua. Using a factorial design, we manipulated aphiddensity (0, 50, 200, or 400 aphids per leaf) within the presence or absence of thepredatory lady beetle, Hippodamia convergens. We recorded the impact of thesemanipulations on the survival of the beet armyworm. Concentrations of defensiveproteins: trypsin inhibitor, peroxidase and chitinase were analyzed in leaf tissuesexposed to increasing aphid densities. Moreover, in separate experiments weexamined expression of selected genes from salicylic acid (SA) and jasmonic acid(JA) defense pathways through quantitative PCR. We found that concentrationsof defensive compounds in leaf tissue increased with higher aphid density, butsurprisingly, greater abundance of aphids alone did not systematically decreaseS. exigua survival. H. convergens and aphid-induced plants suppressed S. exigua,and combined effects were synergistic at moderate aphid densities. Yet, at highaphid density, predation of S. exigua was reduced, perhaps as a result ofchanging predator behavior. Furthermore, we found that genes regulated by SAas well as JA were induced by aphid herbivory. While aphids commonly stimulatetranscription of genes involved in pathogen response in plants (SA), theirinduction of genes elicited by chewing herbivores (JA) suggests that aphids mayalso prime defenses against more damaging herbivores. Overall, our resultssupport a net benefit of aphids to suppress more damaging herbivores via aphid-induced defenses and apparent competition at moderate densities.

Symposium: The scientific ‘‘toolbox’’ for the study of plant-insectinteractions. Anna-Maria Botha-Oberholster, Moderator

The co-regulation of caterpillar and plant defense genes. RichardMusser (Western Illinois University, Macomb, IL), B. DesRochers, H. Vogel & S.Hum-Musser. The relationship between plants and insects is incredibly intricate,involving complicated cascades of biochemical pathways. Nicotine is an alkaloidsynthesized in the roots of tobacco plants and transferred systematically in theplant in response to insect damage. Nicotine functions as an inducible chemicaldefense compound upon herbivory. While at the same time, the fate of thecaterpillar is dependent on its digestive performance and the ability to overcometoxic components of its diet. This is especially true for natural plantallelochemicals. Insects use detoxification genes such as cytochrome P450s, andglutathione S-transferases that are known to be inducible by xenobiotics, and areinvolved in host plant adaptation. In this experiment, tobacco plants were grown

STOUT et al.: IPRI Workshop 109

from seeds in an environmentally controlled growth chamber for 8 weeks. Sixthinstar Helicoverpa zea caterpillars were caged onto individual tobacco leaves, onecaterpillar per plant, and allowed to feed for 24 h, periodically repositioning thecage to ensure optimal herbivory. The leaves and the caterpillars were harvestedand RNA was purified from each sample (plant and caterpillar) and labeled withcyanine 3 or cyanine 5 dyes, which then was hybridized onto tobacco oligo-microarrays. Analysis of the arrays produced hundreds of significantly alteredgenes in both the tobacco plant and caterpillar in comparison to their controls.The results in this study show how tobacco plants respond to caterpillarherbivory and with the advent of caterpillar microarrays we can show for the firsttime how caterpillars respond on a genomic scale to these challenges.

The proteomics toolbox for agricultural research: Precision biomark-er discovery using genetics. Michelle Cilia (Cornell University, Ithaca, NY),C. Tamborendeguy, K. Howe, T. Fish, T. Thannhauser & S. Gray. The vast arrayof proteomics technologies can often leave investigators wondering which set oftools to use to address their biological question. Deciding which set of tools toapply requires knowledge of the biology of the system and of the subtleties of eachproteomics approach. Proteomics approaches can be broadly categorized as top-down, bottom-up, or a combination of both. One application of top-downproteomics separates a complex mixture of intact proteins using 2D gels tomeasure the molecular weight and isoelectric point of the proteins and theirvarious isoforms in the sample. Proteins are enzymatically digested from the gelspots and identified using mass spectrometry. Bottom-up methods accomplishprotein identification differently. The entire complex protein sample is firstdigested with a specific protease (e.g., trypsin). The presence of particularproteins is inferred from the identification of a subset of its constituent peptidesafter multidimensional chromatography and mass spectrometry (LC-MS/MS).Our lab studies the aphid transmission of yellow dwarf viruses. By crossing acompetent genotype and refractive genotype, we generated an F2 population ofaphids that differ in virus transmission competency. We applied a combination ofapproaches to investigate the proteomes of the aphid genotypes that differ intheir transmission capacity. Combining aphid genetics with the top-downquantitative intact proteomics (QIP) technique, 2D fluorescence difference gelelectrophoresis (DIGE), and LC-MS/MS, we identified more than 35 aphidproteins whose expression level correlates with differences in the intercellulartransport of yellow dwarf viruses across aphid gut and salivary tissues. Thecombination of genetics with the initial top-down approach facilitated twoexciting discoveries in our system that would not have been identified had weused any other approach. The first unexpected discovery was the implication ofbacterial endosymbionts of aphids as playing an important role in determiningvirus transmission competency. Secondly, we discovered that several of the aphidand bacterial proteins have practical importance in that they serve as robustbiomarkers for distinguishing transmission competent and transmission refrac-tive populations of aphids. Not only are these the first protein biomarkers forvirus transmission in any insect, they are the first protein biomarkers for anyphenotypic trait discovered using a top-down proteomics approach. This workopens the door for novel virus and integrated pest management strategies.

Profiling metabolites in wheat plants in responses to Hessianfly infestation. Lieceng Zhu (Fayetteville State University, Fayetteville, NC),


M.-S. Chen & X. Liu. Infestation of Hessian fly in wheat plants causeddistinctively different reactions between compatible and incompatible interac-tions. To study the molecular basis of wheat resistance and susceptibility, weinfested a wheat genotype ‘‘Molly’’ with an avirulent biotype GP and a virulentbiotype vH13, respectively. In the first step, we applied gas chromatography-mass spectrometry (GC-MS) technology to analyze contents of 82 uniquemetabolites at Hessian fly larval feeding sites in the uninfested control, thecompatible interaction and incompatible interactions at 72 h following initialattacks. Our study revealed that Hessian fly attacks significantly decreased thecontent of free carbon-containing compounds but increased the content of freenitrogen-containing compounds in both interactions. Further analysis throughNorthern blot hybridization suggested that the C/N shift in the compatibleinteraction was achieved through a coordinated regulation of genes in glycolysis,tricarboxylic acid cycle, and amino-acid synthesis in the compatible interaction.To study the regulation of resistance and susceptibility of wheat plants toHessian fly infestation, we determined contents of 10 phytohormones andphytohormone-related compounds. We found that, in 24 and 72 h following initialattacks from Hessian flies, contents of 12-oxo-phytodienoic acid (OPDA), salicylicacid (SA), and 18:1 and 18:3 fatty acids increased significantly in theincompatible interaction but remained at control level in the compatibleinteraction, while auxin (AUX) increased significantly in the compatibleinteraction but remained at control level in the incompatible interaction. Resultsof phytohormone analysis suggested that OPDA and SA played important roles inregulating resistance, and that AUX were critical to susceptibility. Furthermore,we analyzed contents of 130 polar lipid species using an automated electrosprayionization-tandem mass spectrometry approach at feeding sites of Hessian flylarvae in wheat plants. We found that Hessian fly infestation caused substantialdegradation of the major plastidal lipids monogalactosyldiacylglycerol (MGDG)and digalactosyldiacylglycerol (DGDG). The degradation of MGDG and DGDGcould be an important source for the enhanced content of 18:3 needed in OPDAsynthesis in the incompatible interaction. To summarize, our study revealed thatHessian fly infestation caused significant changes in various metabolic pathwaysof wheat plants, and that metabolic profiling is a powerful tool in studying plants-insects interactions.

Virus-induced gene silencing as a tool for fast analysis of genefunction in tomato plants. Johannes Stratmann (University of SouthCarolina, Columbia, SC) & S. R. Hind. In many crop plants, reducing genefunction via stable genetic transformation (e.g., RNAi) is a laborious, lengthy,and sometimes difficult process. Virus-induced gene silencing (VIGS) representsa convenient, relatively fast alternative. Most plant viruses are single-strandedRNA viruses. During replication, they produce a double-stranded RNAintermediate which is recognized and degraded by the post-transcriptional genesilencing (PTGS) machinery. PTGS then uses small stretches of the degradedviral RNA to target other homologous RNA for degradation. This phenomenonwas exploited to purposefully silence plant genes of interest by including partialsequences of these genes into the genome of a virus that triggers VIGS. Themanipulated virus is then used to infect plants. Since PTGS is a homology-basedprocess, transcripts of endogenous genes with homology to the inserted sequenceof interest will be degraded along with the viral RNA. VIGS has been used for a


range of crop plants. In each case, the viral species has to be carefully selected toavoid disease-like symptoms caused by the virus. Here, we present the use ofVIGS to silence genes in tomato using the tobacco rattle virus (TRV) as a VIGStrigger. We successfully silenced two closely related genes simultaneously, andwe used UTR sequences to silence specific members of a gene family. In addition,we combined sequences of unrelated genes to co-silence them. Efficiency of genesilencing can be assessed by measuring transcript levels or protein levels. Weobtained various degrees of silencing, depending on the gene or the partialsequence selected for silencing, ranging from 0 to .90% (at the protein level).Null mutants of some genes or strong gene silencing in RNAi plants causelethality and prevent studying the effect of these genes on stress responses. Thisis a lesser problem for VIGS since it takes effect at later stages of development.Examples will be presented that demonstrate the usefulness and efficacy of VIGSto study resistance of tomato against herbivores and pathogens.

Exploring the genetic architecture of plant defense in poplar treesusing forward genetics. Steven Ralph (University of North Dakota, GrandForks, ND). As sedentary organisms, plants cannot avoid or escape biotic andabiotic stresses in their local environment. Instead, plants have evolved anenormous diversity of anatomical structures and chemical defenses to protectthemselves. In response to attack by feeding insects, plants deploy a diversity ofdefense mechanisms that are tightly regulated. Researchers have utilizedtransciptomics and proteomics technologies to profile insect herbivory-inducedchanges. However, it remains to be determined if altered expression of individualgenes directly contributes to successful plant defense or are simply correlatedwith the defense response. One of the most successful approaches to identifygenes responsible for variation in a trait of interest is to produce mutants that arethen screened for alterations in the trait (i.e., forward genetics). Our laboratory isexploring the genetic architecture of plant defense in poplar (Populus spp.) usingseveral populations of activation tagged mutants. Extensive genomics resourcesare available for this model perennial plant of economic importance to the forestindustry. In the activation tagging method, one or more endogenous genes (i.e.,present in the wild-type plant genome) are ‘‘turned on’’ by the random insertion ofan activator element (4 3 CaMV 35S enhancer) near endogenous promoters. Inthe mutant plants, the pattern of activated gene expression is the same as inwild-type plants, but the level of expression is enhanced, thus altered phenotypesare related to normal endogenous gene function. Here I will discuss the pros andcons of using forward genetics to study plant-insect interactions, and will alsopresent the results of our first bioassay screen of 600+ mutant lines, along withfollow-up studies to validate the resistance phenotype of the insect resistantmutants IR1 and IR2.

Systems biology-guided analysis of plant-insect interaction. Joshua S.Yuan (Texas A&M University, College Station, TX), P. Gao, C. Di, W. Shi & Y.Zhang. Plants respond to insect attack at different levels. In order to understandthe plant defense against herbivorous insects thoroughly, we developed variousmodels and methods for proteomic, interactomic, and transcriptomic analysis ofplant responses toward herbivorous insects. First, we have developed a novelprotein extraction method to remove the abundant protein for shot-gunproteomics analysis. The method has been applied to the plant-insect interactionanalysis and has greatly improved the protein identification and differential


expression analysis. Second, we have developed various methods to carry out thegene co-regulatory network analysis. The analysis integrates the meta-analysisof microarray data and has revealed many important genes involved in plantinsect interaction. Third, we have developed a novel high-throughput platformfor plant interactome mapping, and the method is applied to the plant insectinteraction analysis. With all these methods, we have identified multiple genesthat are important for the plant defense against herbivorous insects inArabidopsis. In particular, we have found that selective protein degradationcould be an important mechanism to regulate the plant defense againstherbivorous insects.

Symposium: Comparing plant resistance in model systems: Toward thedevelopment of a general framework for understanding plant resis-

tance. C. Michael Smith, Moderator

H gene-mediated resistance to Hessian fly exhibits features ofpenetration resistance to fungi. Marion O. Harris (North Dakota StateUniversity, Fargo, ND), T. P. Freeman, J. A. Moore, K. G. Anderson, S. A. Payne,K. M. Anderson & O. Rohfritsch. The Hessian fly is unusual in being the specifictarget of gene-for-gene plant resistance, a form of resistance that is important inplant pathology but rarely discussed in entomology. The grass hosts of theHessian fly, including wheat, have H genes, each of which confers a plantsurveillance system that detects a specific Hessian fly larval effector (encoded bya specific Hessian fly avirulence gene). In gene-for-gene resistance, detection bythe surveillance system triggers induced resistance. This is what kills theHessian fly larva. Little is known about the cellular mechanisms that contributeto induced resistance. We used imaging techniques to examine how resistantepidermal cells respond to Hessian fly attack. Four near isogenic wheat lineswere tested: a susceptible genotype and four resistant wheat genotypes (H6, H9,H13, and H26). On both resistant and susceptible plants, larvae used their tinymandibles (0.1 mm diameter) to attack the tangential cell wall. Resistant plantsfailed to show two features observed in susceptible plants, a nutritive tissue (agall-like tissue that the larva induces and feeds upon) and ruptured cell walls.Instead resistant plants showed features of induced resistance, which includeddying cells and adjacent living cells with fortified walls. Cell death and fortifiedwalls could limit the larva’s access to food, as well as preventing the cell-to-cellmovement of signals required for the creation of the nutritive tissue. The livingcells that were adjacent to dying cells showed a number of subcellular responses,including the production of vesicles by an elaborated endoplasmic reticulum (ER)-Golgi complex. An association between cell wall fortification and vesiclesoriginating from the ER-Golgi complex also has been found in plants that areresistant to fungi. This suggests that cellular mechanisms of induced resistancemay function against both pathogens and insects.

Co-evolution of the rice blast resistance gene Pi-ta and Magnaportheoryzae avirulence gene AVR-Pita1. Yulin Jia (USDA-ARS, Stuttgart, AR).The Pi-ta gene in rice provides resistance to races of Magnaporthe oryzae thatcontain the corresponding avirulence gene AVR-Pita1. Pi-ta encodes a predictedreceptor protein with nucleotide binding site and leucine rich repeat domain (NBS-LRR) that directly recognizes the products of AVR-Pita1 inside plant cells


triggering resistance responses. AVR-Pita1 encodes a predicted metalloproteasethat may be involved in pathogen pathogenicity and fitness. Surveys thus far haveonly identified one resistant Pi-ta protein in diverse rice germplasm collections.Moreover, an intact transposon was identified within the Pi-ta promoter region inresistant rice accessions. Such a transposon was not found in susceptible ricegermplasm accessions. Expression analysis using semi-quantitative RT-PCR showthat Pi-ta can produce a total of 12 proteins, most of which contain NBS-LRRdomains. In contrast, 27 AVR-Pita1 proteins with minor amino acid alterationswere identified from avirulent field isolates. Deletion, point and frame-shiftmutations, and transposon insertions were predicted in virulent avr-pita1proteins. These findings suggest Pi-ta engages in trench warfare with AVR-Pita1.

Resistance and virulence in the soybean-Aphis glycines interaction.Curt Hill (University of Illinois, Urbana, IL) & G. Hartman. Aphis glycinesMatsumura, the soybean aphid, first arrived in North America in 2000 and hassince become the most important insect pest of domestic soybean, causingsignificant yield loss and increasing production costs annually in many parts ofthe soybean belt. Work to identify sources of resistance to the pest began shortlyafter it was identified and several sources were quickly identified in the USDAsoybean germplasm collection. Characterization of resistance expression andmapping of resistance genes present in resistant germplasm accessions hasresulted in the identification of five named soybean aphid resistance genes: Rag1,Rag2, rag3, rag4, and rag1-provisional, that express antibiosis-type resistance.Simple sequence repeat (SSR) markers flanking the resistance genes wereidentified, facilitating public and private soybean breeders’ efforts to use marker-assisted selection to develop advanced resistant soybean lines and commercialcultivars. Saturation or fine-mapping with single nucleotide polymorphism (SNP)markers narrowed down the genomic regions containing Rag1 and Rag2 genesand two NBS-LRR candidate genes for Rag1 and one NBS-LRR gene for Rag2were found within the regions. Years before the release of the first resistantsoybean cultivar in 2009 with Rag1, a soybean aphid biotype was found that couldovercome the resistance gene. Recently, a biotype was identified that can colonizeplants with Rag2 and other resistance genes. At present, three biotypes havebeen reported that can be distinguished by their virulence on Rag1 and Rag2resistance genes. Frequency and geographic distribution of soybean aphidbiotypes are unknown. Work has begun to determine the inheritance of virulenceand develop DNA markers tagging virulence genes to facilitate monitoring ofbiotypes. Preliminary results indicate that virulence on Rag1 is recessive toavirulence.

Utilizing genetic tools of Medicago truncatula to dissect mechanismsof insect resistance. Kenneth L. Korth (University of Arkansas, Fayetteville,AR), L. D. Nelson, W. G. Navia-Gine & A. B. More. Although developed primarilyas a model system for plant interaction with symbiotic microbes, Medicagotruncatula Gaertn. has emerged as a useful organism for study of other plant-biotic responses. Consolidated efforts at developing genome-scale information,along with the growing genetic toolboxes available in M. truncatula, haveincreased the speed of discovery in this system. It has clearly become one of themost useful plant systems for studying legume biology. However, our knowledgeof M. truncatula resistance mechanisms to pests is still somewhat limited. Anoverview of M. truncatula as a model system, along with an assessment of our


current knowledge of its resistance to insects will be discussed. Clearly, at acellular level M. truncatula utilizes many of the common signaling pathways anddefensive products that are observed in other plant systems. For example, geneexpression profiles indicate strong induction of products encoding proteaseinhibitors, lipoxygenases, and enzymes in terpene biosynthesis. In particular,several terpene synthases are strongly induced and enzymatic characterization,along with measurement of volatile organic compounds, demonstrate that thegene induction correlates with release of defensive volatile terpenes. Phytohor-mones such as jasmonic acid (JA) also appear to play a role in wound-defensesignaling. Exogenous treatment with JA renders plants much more resistant tolepidopteran pests. In addition to induced chemical defenses, M. truncatulautilizes calcium oxalate crystals as an effective structural defense againstchewing insects. The size and localization of these crystals appear to be importantfactors in how they function in defense. The non-allelic mutants available forcalcium oxalate formation in M. truncatula, along with the clear demonstrationthat crystals afford effective resistance, suggest that this species can be avaluable model for physical defenses against insects. Furthermore, the findingsmight have important implications for resistance mechanisms in the many otherplant species that form mineral crystals in a range of tissues.

Foliar resistance to fall armyworm injury in corn germplasm lines.Xinzhi Ni (USDA-ARS, Tifton, GA), Y. Chen & G. D. Buntin. Fall armyworm[Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)] is one of the mostimportant insect pests causing significant economic losses on both monocot anddicot crop plants (such as corn, rice, and cotton) worldwide. Three corn (Zeamays) germplasm lines, ‘Ab24E’ (susceptible control), ‘Mp708’ (resistant control),and a newly-selected partial inbred line ‘FAW7050’ (resistant), were examined forS. frugiperda resistance under the field and greenhouse conditions. Both fieldand greenhouse experiments were conducted with artificial infestation at 6-leafstage to determine S. frugiperda resistance and their underlying resistancemechanisms. The field experiment showed that FAW7050 and Mp708 were moreresistant to S. frugiperda than Ab24E (the susceptible control). The naturalenemies on plants in the field were recorded at pre-infestation and 7d afterinfestation on the infested and uninfested plants, respectively. There was nodifference in natural enemy counts among the three entries at either pre-infestation or at 7d after the infestation on the infested plants. But, theuninfested FAW7050 plants were more attractive to natural enemies than Mp708at 7d after the infestation. Among the seven species of natural enemies recordedon the corn plants, the spotted lady beetle [Coleomegilla maculata (De Geer)],minute pirate bug (Orius spp.), and big-eyed bug (Geocoris spp.) were the mostabundant in the field. The greenhouse experiments were conducted to elucidatenutritional and biochemical bases for S. frugiperda resistance in the corn lines.Nutritional parameters included total protein, amino acids, glucose, total non-structural carbohydrates (TNC), and protein to TNC ratios (P:C), whilebiochemical indices included the enzyme activity assays of peroxidase andlipoxygenase 3 of the corn leaf samples. Physiological changes measured byphotosynthetic rates were also used to explain nutritional and biochemicaldynamics among the corn lines with and without insect damage. The resistancemechanisms of the three corn lines to S. frugiperda were likely to be acombination of varying natural enemy attractiveness in the field, nutritional and


biochemical parameters (e.g., the P:C ratio and total protein content, andperoxidase activity), and photosynthetic capacity.

The Mi-1.2 gene in tomato: A model for analyzing the specificity of Rgene-mediated insect resistance. Fiona L. Goggin (University of Arkansas,Fayetteville, AR), G. R. Palliparambil, F. Francis & J. Reese. Mi-1.2 is a singledominant resistance gene (R gene) in tomato that confers resistance againstcertain biotypes of the potato aphid, Macrosiphum euphorbiae, and several othervascular-feeding herbivores, including the sweetpotato whitefly Bemisia tabaci,the tomato psyllid Bactericerca cockerelli, and certain species of root-knotnematode, Meloidogyne spp. It is a member of a family of plant genescharacterized by nucleotide-binding and leucine-rich repeat (NB-LRR) motifs,and many family members confer race-specific resistance against plantpathogens. As the first NB-LRR gene with known activity against insects, it isan excellent model system in which to investigate mechanisms of R gene-mediated herbivore resistance, as well as the factors governing the specificity ofbiotype-specific insect resistance. To determine the tissue localization of Mi-dependent aphid resistance, we utilized the direct-current electrical penetrationgraph (DC-EPG) technique to examine the impact of resistant plants on aphidbehavior. Our findings indicated that resistance involves factors in theextracellular spaces of the mesophyll and/or epidermis, in addition to factors inthe phloem that curtail ingestion from the sieve elements. An implication of thisfinding is that resistance could potentially also influence organisms that are notlimited to the phloem, such as mesophyll feeders. DC-EPG analysis of differentpotato aphid clones also revealed that the relative effectiveness of the differentresistance factors varies among different insect populations. A ‘‘semivirulent’’aphid population was identified that can colonize resistant plants due to itsability to establish short feeding bouts on these plants. Analysis of the proteinprofile of this aphid on resistant and susceptible hosts using 2D-DIGE suggestedthat aphid endosymbionts are responsive to aphids’ host plants, and may play arole in aphid adaptation to resistance.

Student Competition Papers. Lee French, Moderator

Arabidopsis defense against green peach aphid: Role of trehalosemetabolism. Vijay Singh (University of North Texas, Denton, TX), J. Louis, B.Ayre & J. Shah. Myzus persicae (Sulzer), Green peach aphid (GPA), is a generalistfeeder and a well known pest of over a hundred economically important plantspecies. We have established a GPA-Arabidopsis thaliana model system in ourlaboratory to identify and characterize genes involved in plant defense againstaphids. Using this system, we identified TPS11 (Trehalose-6-Phosphate Syn-thase11) gene from Arabidopsis to be involved in defense against GPA. GPAbioassays and Electrical Penetration Graph (EPG) studies with tps11 mutantplants demonstrated that TPS11 is involved in both antibiotic and antixenotic typeof defenses against GPA. TPS11 encodes for a class II trehalose phosphate/synthase. Both sucrose and starch metabolism is altered in response to GPAfeeding in both wild type and mutant plants indicating that Arabidopsis employsits physiological processes as a presumptive measure against GPA feeding.

Profiling of wounding and Diuraphis noxia-induced transcripts inhexaploid wheat using cDNA-AFLP analysis. Thia Schultz (Stellenbosch


University, Matieland, South Africa) & A.-M. Botha-Oberholster. As a pest thathas a major impact on yield and production of wheat, the Russian wheat aphid(Diuraphis noxia Kurdjomov) is of particular interest to the research andcommercial fields alike. Various Diuraphis noxia (Dn) resistance genes have beenidentified in wheat, but none have been fully characterized or cloned. Dn1 confersan antibiotic resistance, similar to plant defense against pathogen attack, whileDn2 confers a tolerance for aphid infestation. We aimed to investigate thebiological pathways activated by wounding as well as Dn1 and Dn2 duringinfestation. We used material from susceptible ‘Betta’ and two of its resistantnear isogenic lines, ‘BettaDN’ and Betta Dn2. One hundred-fifty transcript-derived fragments (TDFs) from cDNA-AFLPs were cloned for putative identifi-cation. Wounding was found to involve Ca2+ signaling, photosynthesis, energyproduction, protein anabolism, and catabolism. Interestingly, the woundingresponse seems to be altered by the presence of the Dn genes suggesting crosstalk between the pathways. TDFs involved in Dn1 mediated resistanceimplicated elicitor recognition, ion flux, and chloroplast proteins involved indetoxification during oxidative stress. Dn2-mediated tolerance was found toregulate TDFs involved in homeostasis, chloroplast proteins, and energyconservation. Therefore, the Dn1 mode of resistance seems to be associated witha hypersensitive mediated defensive response (i.e., systemic response). In theDn2 type of resistance, results suggest that the tolerance response is a function ofmaintenance of chloroplast function and cellular homeostasis that may be as aresult of a timely recognition event.

Interactions among biological control, cultural control and barleyresistance to the Russian wheat aphid, Diuraphis noxia (Kurdjumov), inColorado, Kansas and Nebraska. Paola A. Sotelo (Kansas State University,Manhattan, KS) & C. M. Smith. The Russian wheat aphid, Diuraphis noxia(Kurdjumov) (RWA) is an important pest in the U.S. Western Plains, causinghundreds of millions of dollars of losses to wheat and barley production throughreduced yields and increased pesticide treatment costs. The objectives of thisresearch were to determine the effectiveness of early planting date as a RWAcultural control, determine compatibility between early planting date and RWA-resistant barley varieties, and to evaluate the compatibility between resistantvarieties and predator and parasitoid biological control agents of RWA. Theresearch was conducted in three experimental barley fields located in Colorado,Kansas, and Nebraska during 2007, 2008, and 2009. The experimental designused was a split-plot design with two main plot treatments (early and normalplanting dates). Four split-plot treatments (barley varieties) were randomizedwithin each main treatment plot. Variety treatments included the ‘Stoneham’and ‘Sydney’ (RWA barley-resistant varieties), and the susceptible variety ‘Otis’under thiamethoxam-protected and unprotected regimes. Sampling of RWA andnatural enemy populations was conducted on four dates from late May throughearly July. RWA populations in early planting date (1st week of March) plots weresignificantly different from those in normal planting date plots in 2007 and 2008for the Colorado and Kansas locations. Within early planting date samples, RWA-resistant varieties yielded RWA populations similar to those in insecticide-treated ‘Otis’ plots at the Colorado site. In contrast to the Colorado site, very lownumbers of RWA were present at the Kansas site, and there were no cleardifferences in RWA population numbers between varietal treatments. Very low


RWA populations were present at the Nebraska site at both dates and there wereno differences in RWA populations between varieties.

Virus-induced gene silencing in wheat alters the aphid resistanceresponse. Leon van Eck (Colorado State University, Fort Collins, CO), T.Schultz, J. E. Leach, S. R. Scofield, F. B. Peairs, A.-M. Botha-Oberholster & N.L.V. Lapitan. Virus-induced gene silencing (VIGS) technology is emerging as aviable reverse genetics approach in cereal crops. However, the potential of VIGSfor determining aphid resistance gene function in wheat has not been evaluated.Many wheat genes are induced during the Russian wheat aphid defenseresponse, but it is unclear which of these genes are essential for the developmentof a resistant phenotype and not merely co-regulated. We report on the use ofrecombinant barley stripe mosaic virus (BSMV) to target and silence two genesdifferentially regulated in resistant wheat during aphid infestation, in order toascertain their requirement for and potential role in aphid defense. A susceptiblephenotype was generated for both knockouts upon aphid infestation, and aphidsfeeding on silenced plants exhibited a significant increase in fitness compared toaphids feeding on control plants. Altered plant phenotype and changes in aphidbehavior after silencing suggest that these genes may play key roles ingenerating a successful resistance response. This study is the first report onthe successful use of VIGS to investigate genes involved in wheat-insectinteractions.

A test of chemical defense and the dual discrimination hypotheses forsugarcane resistance to the sugarcane aphid. Waseem Akbar (LouisianaState University, Baton Rouge, LA), A. T. Showler, J. Davis & T. E. Reagan. J. S.Kennedy (1953, Host selection in Aphididae. Trans. IXth. Internat. Cong,Entomol., Amsterdam 2:106–113) conceptualized the Dual DiscriminationHypothesis of aphid host selection. This postulated that, in addition to specificstimulatory plant secondary metabolites governing botanical preferences,primary metabolites such as amino acids play a major role in aphid hostinteractions. In his Chemical Defense Hypothesis, G. S. Fraenkel (1959, Theraisson d’etre of secondary plant substances. Science 129:245–259) argued thatplant secondary metabolites are exclusively involved in plant defense againstherbivory; therefore, population growth of an insect pest is affected by the levelsof secondary metabolites in the host plant. The target feeding site for aphids isthe sieve elements where phloem sap is present. Phloem sap consists of largequantities of sugars and extremely small amounts of amino acids, both of whichare plant primary metabolites. However, before accessing the sieve elements,aphid stylets penetrate through several layers of cells where secondarymetabolites such as phenolics are present. We tested Kennedy’s and Fraenkel’shypotheses in sugarcane aphid interactions with sugarcane involving cultivarswith different susceptibilities to aphid infestations. Feeding behavior studiesusing the electrical penetration graph technique revealed no differences innumber of ‘‘potential drops’’ and time to access the sieve elements. However,aphids continued to ingest for significantly longer durations in the sieve elementsof the susceptible cultivar compared to the resistant one. Whole-leaf tissueextraction of phenolics indicated no differences between resistant and susceptiblecultivars; however, phloem sap of the resistant cultivar lacked two free essentialamino acids. Analyses of free amino acids in the honeydew indicated that aphidswere able to derive several additional amino acids on the susceptible cultivar, but


not on the resistant one. These studies suggest that the sugarcane aphidresistance factor is located in the sieve elements of sugarcane. Either the absenceof certain amino acids in the phloem sap or aphid’s inability to derive specificamino acids while feeding on the resistant cultivar provides the underlyingmechanism of sugarcane resistance to the sugarcane aphid. These results are inconformity with the Dual Discrimination Hypothesis in the essence that primarymetabolites affect the behavior and performance of sugarcane aphid onsugarcane.

Characterization of onion cultivars for resistance to onion thrips(Thrips tabaci Lindeman) and Incidence of Iris yellow spot virus. JohnDiaz-Montano (Cornell University-New York State Agricultural ExperimentStation, Geneva, NY), B. A. Nault, M. Fuchs & A. M. Shelton. Onion thrips (OT),Thrips tabaci Lindeman, is the most important insect pest worldwide of onions,Allium cepa L. OT can cause yield losses greater than 50%, but can be even moreproblematic when it occurs with Iris yellow spot virus (IYSV) transmitted by OT.IYSV was confirmed in the summer of 2006 in New York. IYSV symptoms includestraw-colored, dry, tan, spindle- or diamond-shaped lesions on the leaves andscapes of onion plants and can cause yield losses up to 60%. In field studies ononion resistance conducted in 2007 and 2008 using 49 cultivars, 11 showed thelowest leaf damage by OT. In 2009, the 11 cultivars, along with 2 susceptiblechecks and 4 additional cultivars were evaluated further to understand therelationship between OT and IYSV infection in more detail. Four plants percultivar were transplanted into a single pot (10 pots/cultivar), and moved to afield where IYSV was present. After 3 week, larvae were counted and plantstested in the laboratory for IYSV using the DASELISA test. Complementaryexperiments to assess transmissibility were conducted in lab conditions byinfesting each pot with 32 OT from IYSV-infected fields. Additionally, categoriesof resistance to OT were examined by performing non-choice tests in which plantswere grown in Cone-tainersTM and OT adults were introduced and the progenycounted after 10 d. Choice tests were performed by planting all the cultivarstogether in a single pot and releasing OT adults at the center of the pot andassessing their preference after 24 h. None of the cultivars was immune to IYSVinfection. The resistant cultivars were confirmed to have both antibiosis andantixenosis as categories of resistance to OT; however, the antixenotic effectseems to be stronger. And, it appears that leaf color is the key determinant forresistance to OT.

The COP9 signalosome controls jasmonic acid synthesis and plantresponses to herbivory. Sarah Refi Hind (University of South Carolina,Columbia, SC), P. Veronese & J. W. Stratmann. The COP9 Signalosome (CSN) isan evolutionarily conserved multi-protein complex that regulates proteasome-mediated proteolysis. While the CSN has been shown to function in variousgrowth and developmental processes, the involvement of the CSN in theregulation of defense responses is largely unknown. Results in our lab suggesta role of the CSN in defense signaling pathways. The role of the CSN in stresssignaling was tested using virus-induced gene silencing (VIGS). We found thatreducing transcript and protein levels of the CSN subunit CSN5 resulted inreduced wound-and herbivory-induced levels of jasmonic acid and reducedexpression of wound-response genes. These plants also showed increasedpathogenesis-related gene expression. Consequently, CSN5-silenced plants were


more susceptible to feeding by Manduca sexta (Lepidoptera) and infection by thenecrotrophic fungus Botrytis cinerea. It was further shown by silencing otherCSN subunits that these effects were due to reducing the activity of the CSNholocomplex. These finding suggest a role for the CSN in regulating jasmonicacid-dependent plant defense responses.

Submitted Oral Presentations (4 Sessions). Nora L. V. Lapitan, James A.Reinert, D. Michael Jackson, and Michael J. Stout, Moderators

Anti-insect properties of grass fungal endophytes for plant resistanceto insects. Steve Clement (USDA-ARS, Pullman, WA). Many temperate grassspecies host Epichloe and Neotyphodium endophytic fungi that produce alkaloidswith anti-mammalian and anti-insect properties. Ergot and lolitrem alkaloidproduction by endophyte-infected (E+) grasses can have deleterious effects ongrazing livestock, whereas insecticidal alkaloids (peramine, lolines) in E+ grasseshave not been linked to mammalian toxicity. Fortunately for the development ofinsect-resistant E+ grasses, diverse endophyte strains exist in nature and seedbanks that produce only insecticidal alkaloids for host plant resistance and otherecological benefits. In this talk, I review the growing deployment of ‘non-mammalian toxic Neotyphodium strains’ in forage grass cultivars for resistanceto a broad spectrum of insects. One noteworthy example is the commercialdevelopment of MaxP tall fescue with a non-toxic endophyte from the USDA-ARSseed bank at Pullman, Washington to protect pastures in Australia and NewZealand from attack by root aphid (Aploneura lentisci), African black beetle(Heteronychus arator), and other serious pests. Additionally, a new venture aimsto capitalize upon the discovery of Neotyphodium fungi in the wild relatives ofbarley and wheat to develop an endophyte-based method to protect cereal cropsfrom biotic and abiotic stresses. With this new development, I conclude my talkby summarizing published and unpublished evidence that globally importantcereal pests (Russian wheat aphid, Diuraphis noxia; Bird cherry-oat aphid,Rhopalosiphum padi; rose grass aphid, Metopolophium dirhodum; Hessian fly,Mayetiola destructor; Cereal leaf beetle, Oulema melanopus) are, indeed,adversely affected by alkaloid-producing E+ grasses. This information willexpand our knowledge of the anti-insect properties of endophyte strains indiverse grasses, thereby improving the deployment of different endophyte strainsand metabolites to protect forage and cereal grass cultivars from important pests.

Global analysis of plant and insect genes involved in mutualadaptation strategies. Marco Herde (Michigan State University, East Lan-sing, MI) & G. A. Howe. Over one million species of insects feed on plants.Consequently, many arthropod herbivores are important pests that cause severeagricultural losses. During the coevolution of plant-insect relationships, plantsdeveloped defensive strategies to minimize insect herbivory, which in turn led tothe development of counter adaptations by herbivores. Anti-nutritional and toxichost defenses that act post-ingestively often involve plant proteins that areadapted to the harsh environment of the insect gut. The plant hormonejasmonate (JA) plays a central role in regulating induced defense responses toa broad spectrum of herbivores. We employed a shotgun proteomic approach toidentify JA-regulated proteins from tomato that are stable during passagethrough the digestive tract of the solanaceous specialist Manduca sexta. This


approach led to the identification of two JA-regulated tomato enzymes, arginaseand threonine deaminase, that retard larval growth by degrading essential aminoacids (arginine and threonine, respectively) in the midgut. We recently expandedthis proteomics-based approach to several economically important crop plant-insect interactions, and identified additional JA-inducible proteins that may haveanti-insect properties. To gain insight into potential mechanisms that enableinsect herbivores to adapt to JA-regulated defenses in tomato, we prepared cDNAlibraries from midgut tissue of M. sexta larvae reared either on wild-type tomatoplants or on jai1 mutant plants that lack the JA receptor and thus fail to expressJA-induced resistance to insect attack. High throughput sequencing of theselibraries using 454 technology identified several M. sexta transcripts genes thatare significantly enriched in one of the two libraries. These results provide newinsight into the mechanisms by which M. sexta larvae actively modify theirdigestive physiology to adapt to JA-regulated host defenses.

Hairy canola-flea beetle (Phyllotreta spp., Coleoptera: Chrysomeli-dae) antixenosis in action. Juliana Soroka (Agriculture and Agri-FoodCanada, Saskatoon, SK, Canada), M. Gruber, J. Holowachuk & L. Grenkow.When GL1 and GL3 genes from Arabidopsis were introduced into a line ofBrassica napus canola, the resulting recombinant seedlings had up to 1600 timesmore trichomes per unit area on developing leaves than did leaves of parentseedlings. Flea beetle, Phyllotreta spp., behavior was observed in no-choice clipcage bioassays containing parental or trichome-enhanced leaves. The new linesalso were tested against flea beetles in laboratory feeding trials at Saskatoon,Saskatchewan, and field trials at Saskatoon and Lethbridge, Alberta, Canada.The increased hairiness deterred leaf contact by flea beetles, leading them to feedless and in an abnormal manner, an important first step in developing cropresistance to the insect.

Intraspecific variation for herbivore-induced responses in cabbage.Colette Broekgaarden (Wageningen University, Wageningen, The Netherlands),E. Poelman, G. Steenhuis, R. Voorrips, M. Dicke & B. Vosman. Larvae of thecabbage white butterfly (Pieris rapae) and cabbage aphids (Brevicoryne brassicae)are serious pests of Brassica crops. In order to develop resistant varieties,knowledge on defense mechanisms against these herbivores is needed. Studyingplant-herbivore interactions at the molecular and ecological level in an integratedway will provide insight into plant defense mechanisms. We take such anapproach to study the interaction of P. rapae and B. brassicae in susceptible andpartially resistant varieties of white cabbage (Brassica oleracea var capitata). AsBrassica full-genome microarrays are not yet available, 70-mer oligonucleotidemicroarrays based on the genome of Arabidopsis thaliana were used to study thetranscriptional response of the white cabbage varieties upon herbivore feeding.By comparing the results, we were able to identify candidate genes for resistanceagainst P. rapae and B. brassicae. A few of these candidate genes were studied inmore detail. Finally, we also investigated the transcriptional profiles of the whitecabbage varieties in relation to herbivore infestation under field conditions. Inconclusion, our data show that intraspecific variation among plants has a strongimpact on their interaction with herbivores, both at the molecular and theecological level.

Managing the introduction of wheat midge resistance in Canadianspring wheat. Stephen Fox (Agriculture and Agri-Food Canada, Winnipeg,


MB, Canada), C. Vera, R. M. DePauw, D. Fenn, O. Lukow, D. Procunier, M.Smith & L. Wise. Resistance to wheat midge (Sitodiplosis mosellana), conferredby the antibiosis gene Sm1, has been introduced into six spring wheat cultivarsstarting with ‘Unity’ and ‘Goodeve’ in 2007. Broad commercial production isforecast for 2010. All cultivars are being commercialized as varietal blends of 90%resistant cultivar and 10% interspersed midge-susceptible refuge cultivar. Theuse of varietal blends is being supported with changes to the rules for pedigreedseed production, development genetic testing capacity to monitor the refugeproportion in pedigreed seed production, and creation of a producer educationprogram. Multilocation experiments are underway to quantify the agronomicvalue of Sm1, the stability of the 90% R:10% S varietal blends, and the impact onend-use quality. In addition, oviposition deterrence and aberrant egg placementbehavior have been identified in current cultivars that offer opportunities tosupplement the resistance provided by the Sm1 gene. The use of varietal blendsto protect the long-term usefulness of Sm1 may offer other unrelated advantagesto crop production and might be a model that could be used to manage.

Investigating the transcriptome of Diuraphis noxia. Anna-MariaBotha-Oberholster (Stellenbosch University, Matieland, South Africa), M.Friend, N. F. V Burger & T. Schultz. Most aphid species do little damage totheir respective food plants; however, Diuraphis noxia, or more commonly knownas the Russian wheat aphid (RWA), is a pest that causes devastation in manycountries in the world. These small (,2mm), green, elongated aphids originatedfrom Central Asia, but today they are found in all wheat producing countries,except Australia. Aphids are sucking insects that feed on phloem sap. Theirmouthparts are modified to form a stylet that penetrates the plant tissue. Aphidfeeding on susceptible wheat cultivars causes extensive damage to the host plant.The molecular basis for the aphid-plant interaction is mostly unknown, and ispredicted to follow a gene-for-gene model. The present study was done toelucidate the effects on RWA gene expression by changing the host. RWA fed on asusceptible host were transferred to another host, where after mRNA wasextracted, cDNA synthesized and cDNA-AFLP analysis done. Transcript-derivedfragments were excised, cloned, and sequenced. Data obtained were analyzedusing the BLAST function and compared to 7 NCBI databases. The results thatwere most consistent through all databases, or had the lowest E-value, were thenaccepted as correct since multiple possibilities presented themselves. The sevendatabases used were the NR database (non-redundant database – containsunedited sequences submitted directly from researchers), GO database (GeneOntology protein sequence database – which compares genes and their productsthrough their attributes), Mit-pla database (Mitochondrial and plasmid data-base), rRNA database (rRNA subset database), Pfam database (protein sequencedatabase), SMART database (Simple Modular Architecture Research Tooldomain family database – compares gene domains for conserved areas), andthe KOG database (Eukaryotic Orthologous Groups database – used to identifyeukaryotic ortholog and paralog proteins). Results from these investigationssuggested an abundance of genes involved in carbohydrate metabolism, carbontransport, digestion of food, stress adaptation, as well as cell metabolism andmaintenance.

Can maize anthocyanins function as resistance molecules tocorn earworm? Eric T. Johnson (USDA-ARS, Peoria, IL), M. A. Berhow & P.


F. Dowd. Insect herbivory of valuable crops increases the probability of fungalinfection in damaged tissues. Mycotoxins, produced by some fungi, are harmful tolivestock and humans. Anthocyanin biosynthesis in maize protects tissues frombiotic and abiotic stresses. Constitutive expression of the maize B1 and C1 genes,which induces anthocyanin biosynthesis, resulted in transgenic plants withvaried phenotypes. Colored leaves with the highest levels of cyanidin, thepredominant anthocyanidin detected in all colored transgenic tissues, wereresistant to corn earworm (CEW) larvae. Colored anthers were resistant to CEWfeeding and reductions in CEW growth were significantly correlated to levels ofcyanidin in the anthers. Cyanidin chloride and cyanidin-3-glucoside chlorideadded to insect diet slowed the growth of CEW larvae. Thus, maize anthocyaninsmay be a useful component of multigenic resistance when expressed inappropriate tissues at certain times.

Contrasting root regrowth in transgenic rootworm-protectedmaize hybrids. Herbert Eichenseer (Pioneer Hi-Bred International, Johnston,IA), F. Burns & J. Burks. Compensatory root regrowth after corn rootworm(Diabrotica spp.) larval feeding is one characteristic to understand maizetolerance/resistance against the pest. Root evaluations of multiple hybrids grownunder different conditions and varying intensities of rootworm damage revealthat different transgenic rootworm protection traits and hybrids differ in theirability to grow new root tissue after rootworm feeding. The consequences of moreroot development for rootworm and crop management will be discussed.

Intra-specific variation in populations of wheat curl mite, Aceriatosichella Keifer. C. Michael Smith (Kansas State University Manhattan,KS), D. Ponnusamy, M. Marimuthu & R. Malik. The wheat curl mite (WCM),Aceria tosichella (Acari: Eriophyiidae), is a perennial global pest of wheatproduction, through direct feeding damage and as a vector of wheat streakmosaic virus (WSMV) and High Plains virus. Feeding by this minute (0.25 mmlong) arthropod causes leaves to curl upward and inward, trapping newlyemerging leaves, which results in plants with reduced grain yields. Virusestransmitted by eriophyoid mites are species-specific. Thus, accurate knowledgeabout the identity of a distinct WCM strain is essential to the development ofeffective control strategies for both WCM and WSMV. Taxonomic work oneriophyoid mites is cumbersome because of their very small size and theexistence of numerous morphologically similar species such as A. tulipae, aspecies infesting onions, garlic, and tulips. Recent molecular evidence indicatesmultiple WCM lineages both within and between continents, but availableinformation is limited. Preliminary investigations involving one mitochondrial(16s rRNA) and two nuclear (internal transcribed spacer1 [ITS1] and adeninenucleotide translocase [ANT]) markers revealed that the Kansas WCMpopulation (WCM-KS) has no intra-specific variation among individuals. DNAsequence data generated from these marker regions revealed 100% similarity tothe WCM-1 lineage prevalent in Australia, where at least two distinct lineagesexist (WCM-1 & WCM-2). Populations from Montana and Alberta, Canada aresimilar to WCM-KS and WCM-1, while the Nebraska population (WCM-NE) is99% similar to WCM-2. The WCM-KS ITS1 sequence was also 99% similar to A.tulipae from India. These data will serve as a platform for the study of NorthAmerican and global WCM phylogeny, in future efforts to understand globalWCM spread and movement. Efforts are underway to identify additional


markers that will provide more accurate information on phylogenic relation-ships between WCM populations.

Resistance to wheat curl mite, Aceria tosichella Keifer, is indepen-dent of initial infestation level. Murugan Marimuthu (Kansas StateUniversity Manhattan, KS), P. A. Sotelo, D. Ponnusamy & C. M. Smith. Thewheat curl mite (WCM), Aceria tosichella (Acari: Eriophyiidae), is a perennialglobal pest of wheat production, through direct feeding damage and as a vector ofwheat streak mosaic virus (WSMV) and High Plains virus. Recent upsurges inWCM and virus incidence warrant identification of new WCM resistance, andimproved laboratory techniques are essential for the accurate identification ofresistance genes. Experiments were conducted to compare plant WCM symptomexpression resulting from placing WCM-infested leaf bits with either known orunknown numbers of mites onto the leaf axils of two-leaf stage plants of wheatgenotypes OK05312 (resistant) and Jagger (susceptible). WCM symptomsassessed included folding (trapping) of new emerging leaves and rolling ofdeveloped leaves. Folding was graded on a 1–3 scale (1 5 none, 3 5 present),while leaves developing after infestation were graded for rolling on a 1–9 scale (15 no rolling, 9 5 100% rolling). Plants infested with leaf bits containing unknownnumbers of WCM provided similar results to plants infested with known numbersof mites. OK05312 was highly resistant (low folding and rolling scores) andJagger was highly susceptible. Additional experiments comparing susceptibilityin Jagger, Ike (susceptible), and OK05312 using a group of mites versus a singlesecond-instar mite infestation produced symptoms in each genotype similar toleaf bit infestation. OK05312 expressed antibiosis after group- and single-miteinfestations (78.5 and 10.5 mites/plant, respectively) compared to Jagger (1573.0and 80.8 mites/plant, respectively). We conclude that wheat WCM susceptibilityis independent of initial mite infestation level, and that infesting plants with leafbits containing unknown numbers of WCM is a rapid, accurate method ofassessing plants for mite reactions. Our future research will assess molecularresponses of these wheat genotypes to WCM infestation.

Combining reflective mulch and host plant resistance to managewhiteflies in watermelon. Alvin M. Simmons (USDA-ARS, Charleston, SC),C. S. Kousik & A. Levi. A study was conducted to evaluate the use of reflectivemulch and host plant resistance for the management of the sweetpotato whitefly,Bemisia tabaci (Gennadius), in watermelon [Citrullus lanatus var. lanatus(Thunberg) Matsum & Nakai]. Whitefly abundance data were collected underboth greenhouse (caged and uncaged) and field conditions. Consistently, areflective mulch treatment resulted in a lower incidence of adult whiteflies ascompared with a standard black mulch treatment, and two whitefly-resistant C.colocynthis (L.) Schrad genotypes, which are wild relatives of cultivatedwatermelon, reduced whitefly populations as compared with standard watermel-on. Results from caged trials suggest no adverse effect of the reflective mulch onpopulations of two species of natural enemies (Delphastus catalinae (Horn), awhitefly predator, and an Eretmocerus sp. whitefly parasitoid). Overall whiteflypopulations were relatively low during the four seasons of field trials (2006–2009). Results from this study suggest that a combination of using reflectivemulch and host plant resistance can additively suppress whitefly infestations,which have particular importance in the fast-growing organic vegetableproduction industry.


Biotypes of the southern chinch bug. James A. Reinert (Texas A&MUniversity, Dallas TX), C. Campos & A. Chandra. Southern chinch bug [Blissusinsularis Barber] populations in Texas have changed significantly frompopulations present in the southeastern U.S. Populations in Florida overcamethe resistance in ‘Floratam’ St. Augustinegrass [Stenotaphrum secundatumWaltz (Kuntze)] in 1987 after the grass had provided resistance for about 14 y offield life. Subsequent releases of ‘FX-10’ (1990) and ‘Captiva’ (2008) cultivarshave provided high antibiosis of chinch bugs (80–100% mortalities of confinedbugs) in Florida. Populations were discovered in south-central Texas in 2005 thatexpressed low antibiosis, #20% mortalities after 7 d of confined feeding onFloratam. Additional sampled populations across the state show that Floratamand FX-10 killed 20% of confined bugs in 7 d while Captiva killed 19% in 7 d andonly 27% in 14 d. Some Texas populations were extremely non-responsive tothese ‘‘resistant’’ cultivars: Floratam (4% mortality), FX-10 (2%), and Captiva(4%) at 7 d, and Floratam (42% mortality), FX-10 (48%), and Captiva (8%) after14 d of confined feeding in no-choice tests. Other populations were highlyvariable: Floratam (80% mortality), FX-10 (88%), and Captiva (54%) after 7 d ofconfined feeding. I believe enough evidence has been developed to designate thevery virulent populations in Texas that has overcome the resistance in Captiva asBiotype 2, with the populations that overcame the resistance in Floratam asBiotype 1, and the original strain of southern chinch bugs that could not surviveon Floratam as the Wild Type. A total of 24 different populations have beensampled, including Texas locations of Longview, Dallas, Waco, Austin, SanAntonio, College Station, Bryan, Wharton, Bay City, Huntsville, Houston, andLeague City.

Virus vector host plant resistance for seed potato IPM. Jeffrey A.Davis (Louisiana State University, Baton Rouge, LA), E. B. Radcliffe, D. W.Ragsdale & C. Thill. Potato virus Y (PVY) and Potato leafroll virus (PLRV) are themost important aphid-transmitted viruses in potato, Solanum tuberosum L.Removing either the virus or the vector will eliminate disease, increase yields,and reduce losses due to quality issues. Unfortunately, North American seedpotato producers have experienced an unprecedented and now decade-long PVYepidemic even with seed potato certification programs focusing on reducing virusinoculum. Current research efforts have focused on reduction of either vectornumbers or virus transmission through host plant resistance. For seven years,174 advanced potato lines were subjected to intensive selection for resistance togreen peach aphid, Myzus persicae (Sulzer) and potato aphid, Macrosiphumeuphorbiae (Thomas). One line that has consistently expressed resistance to bothaphids was crossed with the cultivar Chieftain to produce an F1 population.Aphids were tested for survivorship, development, reproduction, and adultlongevity on 30 F1 progeny. Life tables were constructed and intrinsic rates ofincrease (rm) were calculated. In addition, electrical penetration graphs wereused to record feeding behavior on resistant and susceptible plants. With thesetechniques, we expect to ascertain whether the resistance(s) expressed in ourpotato lines are due to antixenosis or antibiosis and if this can be used to reducevirus transmission.

Cry protein and tannin interaction in transgenic cotton and theireffect on mortality of Helicoverpa armigera (Lepidoptera: Noctuidae).Kamaldeep Singh (Punjab Agricultural University, Ludhiana, India), R. Singh &


A. K. Dhawan. Expression of Bacillus thuringiensis (Bt) insecticidal protein andits control efficacy against Helicoverpa armigera (Hubner) in Bt transgenic cottonNECH 6 (carrying Cry1Ac/Cry1Ab fused gene), JK 1947 (modified Cry1Ac), RCH(Cry1Ac), and NCS 913(Cry1Ac) were investigated at Punjab AgriculturalUniversity, Ludhiana (North India). Cry protein expression was high duringthe early stages of cotton growth and declined in the late season. The expressionof Cry1Ac/Cry1Ab fused gene in NCEH 6 was higher than in the single Cry1Aclines. The leaves of Bt cotton plants were found to have the highest level of Cryprotein, followed by squares and bolls. The larval mortality of H. armigeraneonates was high on dual-toxin cultivars. Genotype independent seasonaldecline in mortality of H. armigera was observed in all the hybrids. The resultsshowed that the toxin content in Bt cotton changed during variable stages of crop,the structure and variety were significant sources of variability. A significantpositive correlation was observed between insecticidal protein and mortality. Incontrast, a negative correlation was found between mortality and tannins. Theresults suggest that plant toxin and tannin interaction in transgenic Bt cottonreduced the toxicity of the Cry protein to H. armigera.

Volatile emissions released from cotton bolls in response to hemip-teran pest damage. David C. Degenhardt (Clemson University, Blackville,SC), J. K. Greene & A. Khalilian. Herbivory results in the release of volatileorganic compounds (VOCs) that mediate numerous ecological interactionsbetween plants, herbivores, and natural enemies. Stink bugs (Hemiptera:Pentatomidae) are an increasing threat to cotton, Gossypium hirsutum (L.),production and directly target fruiting structures (bolls). While much is knownabout the emission of VOCs from cotton foliage, no research has investigated theinfluence of stink bug feeding on the release of VOCs from reproductivestructures. The objective of this research was to investigate VOC emissions fromdeveloping cotton bolls in response to stink bug feeding. VOCs were collectedfrom young bolls damaged by three stink bug species, and analyzed by gaschromatography/mass spectrometry. Healthy cotton bolls emit a mixture of VOCs(mainly cyclic terpenes), and feeding by stink bugs resulted in a 2-fold increase inthe total amount of VOCs released from bolls. Feeding by stink bugs also inducedthe emission of several acyclic terpenes not detected in undamaged bolls. Stinkbugs inject a complex blend of digestive and salivary enzymes into host tissuewhich may contain elicitors of VOC induction. The release of VOCs from cottonbolls in response to hemipteran feeding damage may have implications forindirect defense against stink bug pests.

Herbivore- and elicitor-induced resistance in rice to the rice waterweevil (Lissorhoptrus oryzophilus Kuschel) in the laboratory andfield. Jason C. Hamm (Louisiana State University, Baton Rouge, LA), M. J.Stout & M. R. Riggio. Feeding by herbivores can change plants in ways that makethem more resistant to subsequent herbivory. Such induced responses are better-studied in a number of model dicots than in rice and other cereals. In a series ofgreenhouse and field experiments, we assessed the effects of prior herbivory bythe fall armyworm, Spodoptera frugiperda (J.E. Smith) and of exogenousapplications of jasmonic acid (JA) on the resistance of rice plants to the ricewater weevil, Lissorhoptrus oryzophilus (Kuschel), the major pest of rice in theUnited States. Prior feeding by S. frugiperda and treatment of plants withexogenous JA resulted in increases in the resistance of plants to the weevil.


Increases in resistance were manifested as reduced numbers of eggs and firstinstars associated with armyworm-injured or JA-treated plants relative to controlplants. In field experiments, there was a transient but significant reduction inthe number of immature L. oryzophilus on JA-treated plants relative to untreatedplants. To our knowledge, this is the first example of direct induced resistance inrice demonstrated in small-plot field experiments. We discuss the potential forthe use of elicitor induced resistance in rice.

Submitted Poster Presentations. Michael J. Stout, Program Chair

Software package for leaf are measurement to evaluate insect damageto plants. Sanmin Liu (Texas A&M University, College Station, TX) & J. S.Yuan. Leaf area measurement is one method to evaluate plant damage caused byinsects. In fact, previous research has shown that leaf consumption does notalways correlate with insect growth data. Leaf area measurement thus becomesanother important aspect to evaluating how effectively plants can reduce insectconsumption and increase fitness. Previous tools for leaf area measurementmainly were used for round shaped or other regular shaped leaves. In our study,we developed leaf area measurement tools for irregular leaves like Arabidopsis toevaluate insect consumption. We therefore developed a new software packageusing a pixel-based method, which processes the images of the leaf before andafter damage according to the color value of each pixel. An original image withthe leaf’s contours is recorded first, and then another image is made afterdamage. The comparison between the original leaf images and the damaged oneswill render a percentage of damage and a leaf-area consumption evaluation. Thesoftware is implemented in MatLab and can be broadly applied to various plant-insect interaction studies. The package has greatly improved the quantificationand the evaluation of the insect damage on plants and helped us to screenmutants with potential phenotypes for plant defense.

Viral induced gene silencing of three photosynthesis related genesFBPase, TMP14 and P700 in wheat: Elucidation of their role in themaintenance of photosynthetic machinery during Diuraphis noxiafeeding. Carlo S. Jackson (University of Pretoria, Pretoria, South Africa), N.F. V. Burger & A.-M. Botha-Oberholster. Feeding of Russian wheat aphid(Diuraphis noxia, RWA) on Triticum aestivum L. can have devastating effects oncrop yield. Toxins injected by the RWA cause significant damage to thechloroplasts of the susceptible wheat varieties; however they fail to do the samein resistant counterparts. The ability of a particular wheat host to recognize thepresence of RWA feeding through elicitor recognition determines if a defenceresponse will be activated in time. Different defence mechanisms exist to fend offthe destruction of the aphids but vary in affectively maintaining crop yield.Photosynthesis related genes including TMP14, FBPase and P700, previouslyreported to be involved in resistance, were silenced in resistant wheat lines. Itwas found that photosynthesis plays a key role in orchestrating the differentmodes of resistance. Through the results obtained, it is hypothesized thatTugelaDN wheat essentially depends on the ROS produced by the photosynthesisreactions to furnish the hypersensitive reaction. The hypersensitive reactioncauses necrotic lesions and effectively reduces RWA reproduction. Tugela Dn2’stolerance mechanism, however, depends on a fully functional photosynthesis


system to provide carbon flux for maintenance reactions. The Gamtoos Dn7’sdefense mechanism, on the other hand, depends on both the ROS scavenging andcarbon flux. These mechanisms are elucidated with aphid fecundity, geneexpression, and photosynthesis studies.

Green peach aphid–Arabidopsis thaliana interaction. Joe Louis (Uni-versity of North Texas, Denton, TX), V. Singh, K.-L. Kukula, J. C. Reese & J.Shah. Aphids are important pests of plants that cause substantial loss in plantproductivity. In contrast to the chewing insects, aphids utilize their long slenderstylet to feed continuously from the sieve element of plants for extended periodsof time. Green peach aphid (GPA; Myzus persicae Sulzer) is an important pest ofover 100 plant species. In addition, it vectors viral diseases. We have utilized theinteraction between the model plant Arabidopsis thaliana and the GPA to studyplant defenses against aphids and identified Arabidopsis PHYTOALEXINDEFICIENT4 (PAD4) gene as an important modulator of antixenosis (feedingdeterrence) and antibiosis (affect aphid fecundity) mechanisms against GPA. Wewill provide evidence that the MPL1 (MYZUS PERSICAE INDUCED LIPASE1)gene is another critical component of Arabidopsis defense against GPA. LikePAD4, MPL1 expression is induced in response to GPA infestation. However,unlike PAD4, MPL1 is not required for antixenosis. Comparison of GPA feedingbehavior revealed that there was no significant difference in the total duration ofthe sieve element phase (SEP) spent by GPA on the mpl1 mutant and WT plant,suggesting that the mpl1 mutant allele does not impact aphid feeding behavior.Petiole exudates of the mpl1 mutant lack an antibiosis factor that is present insimilar exudates of wild type plants. Furthermore, the over expression of MPL1resulted in enhanced antibiosis against GPA, but had no effect on antixenosis,confirming that MPL1 is only required for antibiotic defenses. The MPL1 proteincontains a conserved Ser-Asp-His triad that is found in a/b fold acyl hydrolasesand recombinant MPL1 protein exhibits lipase activity. We propose that alipid(s), or a product thereof, is involved in Arabidopsis antibiosis to GPA.

Investigating plant resistance to insect herbivores using activation-tagged poplar trees. Heidi Connahs (University of North Dakota, GrandForks, ND), J. Burum, G. Mocelin, S. Regan & S. G. Ralph. Poplar trees arekeystone species in the Northern Hemisphere and serve as major contributors tothe forest industry. Like many perennials, poplars are under constant threat ofattack from herbivores. Insect defoliators cost the forest industry billions ofdollars and subsequent tree mortality can radically alter the landscape. As plantscannot move to escape attack, they have evolved a suite of constitutive andinducible defenses to deter insect feeding. Activation-tagging forward genetics isa powerful tool for linking genotype and phenotype. While this approach has beenwidely adopted for studies in plant physiology and development, its utility forinvestigating the genetic architecture of plant defense against herbivores has notyet been explored. We initially screened a population of 608 activation-taggedPopulus tremula 3 P. alba trees using choice bioassays to identify candidatemutants resistant to feeding by Orgyia leucostigma larvae (white marked tussockmoth, WMTM). Here we report a detailed analysis of the first two mutants, IR1and IR2. Development no-choice bioassays using excised leaf discs wereconducted for 18 d to monitor insect development (data reported here is for12 d). Significant reductions in larval wet-weight gain were observed on bothmutant lines when compared to larvae reared on wild-type trees (WT) with an


18.4% reduction on IR1 (P , 0.01) and a 27% reduction on IR2 (P , 0.001).Furthermore, instar development was also retarded: 61% of larvae on WTreached 3rd instar by day 12 compared to 34% on IR1. Similarly, only 45% oflarvae on IR2 reached 3rd instar compared to 71% on the WT. Our preliminaryfindings suggest that an over-expressed gene activated by the T-DNA insert playsan important role in conferring resistance to the WMTM. Measures of leafconsumption will also be reported. Work is ongoing to identify the activated genein each mutant.

Mi-mediated aphid resistance in tomato: Tissue localization andimpact on the feeding behavior of two potato aphid clones with differinglevels of virulence. Godshen R. Pallipparambil (University of Arkansas,Fayetteville, AR), J. C. Reese, C. A. Avila, J. M. Louis & F. L. Goggin. The Mi-1.2 gene in tomato (Solanum lycopersicum L., Solanaceae) confers resistanceagainst several herbivores, including the potato aphid, Macrosiphum euphorbiaeThomas (Hemiptera, Sternorrhyncha, Aphididae) and the sweetpotato whitefly,Bemisia tabaci Gennadius (Hemiptera, Sternorrhyncha, Aleyrodidae). Previousstudies on the tissue localization of resistance have given varying results;whitefly resistance was attributed to factors localized in the mesophyll orepidermis, whereas aphid resistance was attributed to factors localized in thephloem. Our study utilizes the direct current electrical penetration graph (DCEPG) technique to compare aphid feeding behavior on resistant (Mi-1.2+) andsusceptible (Mi-1.22) tomato plants. This study also compares the impact ofresistance on the feeding behavior of two aphid clones that vary in theirvirulence, or their ability to survive and reproduce on resistant plants. Previouswork had shown that the avirulent WU11 clone is almost completely inhibited byresistance, whereas the semivirulent WU12 clone can colonize resistant hosts.Here, DC EPG analysis shows that both aphid clones take longer to initiate cellsampling and to establish a confirmed sieve element phase on resistant plantsthan on susceptible hosts, and have shorter ingestion periods on resistant plants.However, the magnitude of these deterrent effects is far less for the semivirulentclone than for the avirulent aphids. In particular, WU12 clone is less sensitive tofactors that limit sieve element ingestion, showing shorter non-probe durationand rapidly establishing sustained phloem ingestion on resistant plants whencompared to the WU11 clone. We conclude that, in addition to previously-described factors in the phloem that inhibit ingestion, Mi-mediated aphidresistance also involves factors (possibly in the mesophyll and/or epidermis) thatdelay initiation of phloem salivation, and that act in the intercellular spaces todeter the first cell sampling. Furthermore, the relative effectiveness of thesecomponents of resistance differs among insect populations.

Mi-mediated resistance in tomato (Solanum lycopersicum L.) hasdirect negative effect on two species of minute pirate bugs. Godshen R.Pallipparambil (University of Arkansas, Fayetteville, AR), J. Shapiro & F. L.Goggin. Sustainable agriculture necessitates integration of multiple pestmanagement strategies, including host plant resistance and biological control.This study investigates the compatibility of a source of host plant resistance toaphids in tomato with a generalist biocontrol agent. Previous studies have shownthat the Mi-1.2 gene in tomato confers resistance against certain populations ofthe potato aphid, Macrosiphum euphorbiae, as well as several other phloem-feeding herbivores, including sweet potato whiteflies and tomato psyllids. Tomato


cultivars that carry Mi-1.2 reduce but do not eliminate these pests; therefore, foreffective pest management, this form of resistance must be combined with othercontrol measures like biological control. However, the broad nature of Mi-mediated resistance in tomato opens up the possibility of potential negativeimpacts on non-target beneficial arthropods. Our objective is to evaluate thecompatibility of the Mi-1.2 insect-resistance gene in tomato with two species ofminute pirate bugs that can act as biocontrol agents, Orius insidiosus and O.pumilio. In addition to preying on aphids and other insects, these predators havesupplementary feeding on the plant; furthermore, they oviposit on foliage. Thisdirect contact with the host plant increases the potential of a non-target effect ofhost plant resistance on these natural enemies. We conducted no-choice bioassaysin which the minute pirate bugs were allowed to oviposit, emerge, and feed onresistant and susceptible tomato leaflets. Survival of early instars wassignificantly and negatively impacted by Mi-mediated resistance in tomato forboth insect species. One no-choice bioassay also indicated that emergence of O.insidiosus was reduced on resistant plants. Choice assays suggested that minutepirate bugs were unable to distinguish resistant from susceptible plants, and inmost cases stayed and oviposited on the first plants they fed upon. This is the firststudy to show an impact of resistance gene (R gene) mediated host plantresistance on a non-target natural enemy species. Furthermore, this is also thefirst study to show that Mi-mediated resistance can impact arthropods that feedfrom tissues other than the phloem.

Genetic variability in southern chinch bug (Blissus insularis) popula-tions assessed using AFLP analysis. James A. Reinert (Texas A&MUniversity, Dallas TX), A. Chandra, J. Lamantia & J. B. Pond. Southern chinchbug [Blissus insularis Barber] is one of the most destructive pests of St.Augustinegrass [Stenotaphrum secundatum Waltz (Kuntze)] in the southernUnited States. The present study focused on assessing genetic variability in fivepopulations of southern chinch bugs collected from Texas and Florida. The AFLPtechnique was used to DNA fingerprint individual samples from each population(a total of 46 samples) using five primer combinations (EcoRI/MSeI). Results ofthis study show that the AFLP marker system is a good molecular tool to studygenetic structure of southern chinch bug populations. AMOVA results show noevidence to support significant genetic variability among Texas and Floridapopulations of chinch bugs. The majority of genetic variation was present withinpopulations (95%) and approximately 3% among populations between regions.Low GST values obtained from POPGENE and low FST values obtained from theAMOVA both support the implication of high level of gene flow resulting frominterbreeding and migratory events. The Mantel test shows that there is nocorrelation between the genetic distance and geographic distance matrices of thesampled and tested populations of southern chinch bugs.

Drought stress linked to Mexican rice borer infestation of sugarcanevarieties, and ongoing research on enhancing resistance. Allan Showler(USDA-ARS, Weslaco, TX). Two sugarcane, Saccharum hybrids, varieties weregrown in the greenhouse under well-watered or drought-stressed conditions todetermine the influences of stress on Mexican rice borer, Eoreuma loftini (Dyar),oviposition preference and selected nutritional components in the host plant.Drought induced a wide range of free amino acid accumulations, including 7 of 9detectable free essential amino acids in stalks. Stressed sugarcane was preferred


for oviposition by as much as 40-fold, which was likely related to the greaternumber of dry leaves, elevated nutritional quality, or both. Infestation of stalksby larvae, as determined by numbers of entry holes, was up to 18-fold greater ondrought-stressed stalks, and survival to adulthood was up to 9-fold greater. Whileoviposition preference was not different on excised dry leaf tissue regardless ofthe cultivar or treatment, the configuration of the dry leaf tissue, particularlyfolded leaf edge, had a strong effect on oviposition preference. Ongoing studies onmechanisms of resistance, including dry leaf tissue configuration, resistantcultivars, importance of dry leaf tissue versus biochemical differences in livingtissue, and possible methods of reducing susceptibility through soil amendmentsare discussed.

Differential effect of water stress and Russian wheat aphid biotypeson resistant and susceptible barley. Paola A. Sotelo (Kansas StateUniversity, Manhattan, KS), M. Marimuthu & C. M. Smith. Since its accidentalintroduction in 1986, the Russian wheat aphid, Diuraphis noxia (Kurdjumov)(RWA) has become an important pest of cereals in 16 western-wheat and barley-producing states of the United States. However, RWA damage and populationsvary widely between sites with rain-fed cereal production and in high-droughtproduction areas. The objective of this research was to evaluate the differentialresponse of two barley cultivars to RWA biotypes (RWA1 and RWA2) underdifferent water-stress conditions. The research was conducted under greenhouseconditions using a 2 3 2 3 2 factorial design. Separate experiments wereconducted for RWA1 and RWA2, with Otis, a susceptible variety, and Stoneham,a RWA-resistant variety, ‘irrigated’ and ‘non irrigated’ water treatments, andinfested and non-infested plants. RWA populations, plant symptoms, plant dryweight, and tolerance parameters were recorded in each experiment. Totalphenotypic symptoms were significantly higher on Otis plants, but the severity ofthe symptoms observed depended on the biotype and the irrigation level.Differences in the numbers of RWA were significant depending on variety andbiotype. RWA2 populations were higher than RWA1 populations. Within RWA1,Otis plants yielded higher RWA1 populations than Stoneham. There were higherRWA2 populations on non irrigated plants, but no differences were observedbetween cultivars. Irrigated Stoneham plants tended to yield lower RWApopulations and have lower dry weight change when compared with the nonirrigated plants.

Evaluating jasmonic acid-induced resistance to the fall armyworm,Spodoptera frugiperda, in conventional and transgenic Bt cottons. A.Meszaros (Louisiana State University, Baton Rouge, LA), M. J. Stout, J. M.Beuzelin, M. R. Riggio & B. R. Leonard. Conventional, BollgardH, and BollgardHII cotton (Gossypium hirsutum L.) cultivars having similar pedigrees weretreated with jasmonic acid (JA) to assess potential interactions betweenexpression of Bt toxins and JA-induced resistance to the fall armyworm(Spodoptera frugiperda [Smith]). S. frugiperda performance (relative growthrate and absence/presence) was quantified under laboratory and greenhouseconditions. Overall, JA treatments and Bt cultivars decreased S. frugiperdarelative growth rate. Our results showed that JA treatment had synergisticeffects with Bt toxins against S. frugiperda. This study reinforces the idea thatcombining genetic engineering and traditional breeding could lead to a moreeffective pest management.


A meta-analysis of insect pest behavioral manipulation withplant volatiles. Zsofia Szendrei (Michigan State University, East Lansing,MI) & C. Rodrigues-Saona. This study provides an overview of the currentachievements and challenges of applying plant volatiles in pest management.Using a meta-analysis, we synthesized results from published studies to identifyherbivore and plant traits that may explain pests’ behavioral response to plantvolatiles in field applications. We scored a total of 374 unique plant volatile-insectherbivore interactions obtained from 34 published studies investigating 50herbivore pest species. Attractants had a significant effect on insect herbivoreabundance, with females being significantly more attracted to plant volatile baitsthan males. More studies reported effects of plant volatiles on chewers thanborers or sap-feeders. The diet breadth of herbivores was independent of abehavioral response to plant volatiles. Regarding the mode of plant volatiledeployment in the field, sprayable formulations had a non-significant effect onherbivore abundance. Increasing the number of chemicals in individual baitsattracted more herbivores. Attraction of chewing insects was commonlyassociated with alcohols, aldehydes, and esters in baits, whereas borers weretypically associated with terpenes. Esters and ketones were frequently used inbaits targeting sap-feeders. The magnitude of the response of herbivores to plantvolatiles in forest and agricultural habitats was similar. Our results point outareas, such as a need for novel modes of applications and perfecting ratios ofplant volatile blends, that are lacking and require further research. Thesefindings may be used to guide the future development of plant volatile baits inpest management programs.

Insect interactions in sweetpotato breeding nurseries. D. MichaelJackson (USDA-ARS, Charleston, SC). Sweetpotato, Ipomoea batatas (L.) Lam.(Convolvulaceae), is a vital staple food crop in much of the developing world, andit is an important specialty crop in the United States. American consumers prefersweetpotatoes with sweet, moist orange flesh. After many years of declinebeginning in the 1950s, per capita consumption of sweetpotatoes has shown amodest increase over the past 10 y. This increase has much to do with increasedawareness of American consumers to the health benefits associated withconsuming this nutritious vegetable. Worldwide sweetpotato production has alsoincreased due to interest in this crop as food, biofuel, animal feed, or source ofstarch or neutraceutical products, such as the antioxidants b-carotene andanthocyanins. Unfortunately, many insect pests damage sweetpotato roots in thefield, and for over forty years, there has been an active breeding program at theU.S. Vegetable Laboratory (USVL) to develop pest-resistant sweetpotatocultivars. This program has made significant progress in increasing insectresistance in sweetpotato germplasm with high quality, good yield, and superiordisease resistance. Sweetpotato is a hexaploid and most quality characteristicsare inherited qualitatively, which makes breeding efforts difficult. Also, the cropis clonally propagated from year to year using sprouted roots or greenhousecutting, so once a variety is released, it cannot be improved any further. Forbreeding sweetpotatoes at the USVL, we us a recurrent mass selectionmethodology based on quantitative genetic principles. Key to this method is thepolycross breeding nursery where up to 25 parents are randomly distributedwithin four replicated blocks in an isolated field. These polycross nurseriesdepend on natural pollination by bees and other insects. Unpollinated flowers


dehise and do not produce seeds, thus it is important to protect natural beepopulations in ensure maximum seed production. There are several other insectspecies that frequent sweetpotato seed nurseries that are quite destructive.Foliar feeders, such as armyworms, tortoise beetles, and the sweetpotatohornworm can cause significant damage to sweetpotato plants, but they areeasily controlled. Of much more concern at the USVL is the potato leafhopper,Empoasca fabae (Harris) (Homoptera: Cicadellidae). These insects reach highnumbers, and if not controlled they can severely stunt or kill the sweetpotatoplants in a polycross nursery. They are also difficult to manage because most ofthe insecticides used to control them are also toxic to bees. Sprays of materialswith a short residual activity should be applied in the afternoon after thesweetpotato flowers close and fewer bees are present.

Enzyme activities associated with latex-mediated insect resistance inromaine lettuce. Amit Sethi (Louisiana State University, Baton Rouge, LA),H. J. McAuslane, B. Rathinasabapathi, G. S. Nuessly & R. T. Nagata. Plant latexis a known storehouse of various secondary metabolites with demonstratednegative impact on insect fitness. A romaine lettuce cultivar, ‘Valmaine,’possesses a high level of latex-mediated resistance against the banded cucumberbeetle, Diabrotica balteata LeConte (Coleoptera: Chrysomelidae), compared to aclosely related cultivar ‘Tall Guzmaine.’ Latex from damaged Valmaine plantswas much more deterrent to adult D. balteata feeding than latex fromundamaged plants when applied to the surface of artificial diet under choiceconditions; no such difference was found in choice tests with latex from damagedand undamaged Tall Guzmaine plants. The intensities of whiteness andbrowning were significantly higher in Valmaine latex than in Tall Guzmainelatex. The activities of three enzymes (phenylalanine ammonia lyase, polyphenoloxidase, and peroxidase) significantly increased over time in latex from damagedValmaine plants (i.e., 1, 3, and 6 d after feeding initiation), but they remained thesame in Tall Guzmaine latex. The constitutive levels of phenylalanine ammonialyase and polyphenol oxidase were also significantly higher in Valmaine latexthan in Tall Guzmaine latex. These studies suggest that Valmaine latexchemistry may change after plant damage due to increased activity of inducibleenzymes, and that inducible resistance appears to act synergistically withconstitutive resistance against D. balteata.

Differential gene expression in barley and wheat genotypes resistantto the Russian wheat aphid, Diuraphis noxia. Marimuthu Murugan (TamilNadu Agricultural University, Coimbatore, India), X. Liu, C. M. Smith, S.Starkey & J. Ming. Recognition of aphid feeding in plant tissues involvesproduction of several defense response signaling pathways and downstreamproduction of defense and detoxification compounds. Feeding by the Russianwheat aphid, Diuraphis noxia Kurdjumov, a serious pest of barley and wheat,induces foliar deformity and chlorophyll loss during compatible plant-D. noxiainteractions. Experiments conducted to better understand the temporal expres-sion of barley and wheat genes during compatible and incompatible interactionswith D. noxia, revealed significant differences in the level and pattern ofexpression of defense response transcriptomes. In wheat plants resistant to D.noxia via antibiosis, JA signaling genes were significantly more up-regulated inincompatible interactions than in compatible interactions, as early as 1 h post D.noxia infestation (hpi). In contrast, glycolysis and TCA genes were significantly


down-regulated in incompatible interactions and up-regulated in compatibleinteractions from 6- to 72 hpi. In contrast, incompatible interactions between D.noxia and barley plants with tolerance resistance resulted in expression of auniquely different transcriptome than that in wheat. Numerous growth anddevelopmental pathways genes involved in ET, IAA (auxin), and ABA responsesignals were highly expressed in barley plants in response to D. noxia feeding,and maximum expression was delayed until from 24 to 120 hpi. D. noxia defenseresponse signals in wheat are restricted to aphid feeding sites in the initial 6 hpi.This is the first report of differential up-regulation of plant genes at 1 hpi inincompatible interactions involving aphid herbivory. Early wheat plant defenseresponses in incompatible D. noxia interactions appear to be important aspects ofD. noxia antibiosis resistance in wheat.

Acknowledgments

The 19th Biennial International Plant Resistance to Insects Meeting was sponsored bythe South Carolina Entomological Society and by the USDA-ARS, U.S. VegetableLaboratory (USVL), Charleston, SC. Monetary support for this meeting was provided bythe following corporate sponsors: Dow Agrosciences, French Agricultural Research, Inc.,Landis International, Monsanto Company, E. I. du Pont de Nemours and Company, PioneerHi-Bred International, Inc., Valent U.S.A. Corporation, and Syngenta AG. The IPRISteering Committee sincerely thanks Randy McWhorter, Executive Director of the SouthCarolina Entomological Society, who handled all financial matters, registrations, andprinting of the program for this meeting. We thank Merle Shepard for arranging the detailsof the tour to Wadmalaw Island, and Alvin Simmons for handling audiovisual at themeeting. The assistance of the technical staff at the USVL (Jennifer Cook, Brad Peck, TyPhillips, Paul Wade, & Emily Fillippeli) is also greatly appreciated. Without all of their hardwork and dedication, the success of this meeting would not have been possible.


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