plant disease threats for 2009 wheat viruses stem rust dr. mary burrows montana state university,...
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Plant Disease threats for 2009Wheat viruses
Stem rust
Dr. Mary BurrowsMontana State University, Bozeman, MT
WSMV: The Pathogen
• Family Potyviridae, genus Tritimovirus
• Mite-transmitted virus
Wheat streak mosaic virus• Infects both winter and spring wheat
– Symptoms in spring
• Earlier infection = greater yield loss• Grassy weeds, volunteer wheat, corn, etc.
can harbor both WSMV and the mite vector• 5-10% yield loss/yr across Great Plains• 100% yield loss in individual fields
SDSU Extension
No chemical controls are effective for control of mite or
virus
The life cycle of mite-transmitted wheat viruses
Table 2. Capacity of prevalent grassy weeds in Montana to serve as mite and virus hosts.*Common name Scientific name Life cycle Mite host WSMV hostJointed goatgrass Aegilops cylindricae Annual Yes YesCrested wheatgrass Agropyron cristatum Perennial Unknown UnknownWild oat Avena fatua Annual No YesSmooth brome Bromus inermis Perennial Yes NoJapanese brome Bromus japonicus Perennial No UnknownDowny brome/Cheatgrass Bromus tectorum Annual Yes YesPersian darnell Lolium persicum Annual Unknown UnknownWestern wheatgrass Pascopyrum smithii Perennial Yes NoFeral rye Secale cereale Annual Unknown UnknownYellow foxtail Setaria glauca Annual No NoGreen foxtail Setaria viridis Annual Yes Yes*data taken from literature cited in text
Weed Host: Volunteer Wheat
WSMV in Montana weeds
Plant Ft.Benton Conrad site 1 Conrad site 2Wheat (in crop field) 68/100 42/100 66/ 100Crested wheatgrass 0/25 0/25 0/25Downy Brome N/ A 6/100 0/25Foxtail 0/25 0/25 0/25Wild oat 0/25 0/50 1/25Volunteer wheat 4/50 7/50
Volunteer wheat is the best non-crop host, but weed species are also are infected with virus and may serve as a source
Which weeds are susceptible?Which weeds are susceptible?
Common nameLiteratur
e1 ELISA2
Jointed goatgrass Yes LocalWild oat Yes +Downy Brome Yes LocalCrested Wheatgrass
No -
Thickspike Wheatgrass No -Quackgrass No +Slender Wheatgrass
No -
Smooth Brome No -Barnyardgrass Yes +Green Foxtail Yes -1WSMV host data taken from Somsen 1970, Townsend 1996, and Brey, 1998.2Data from MSU: 'Local' = Virus restricted to inoculated leaves in preliminary assay
Regional variation in the susceptibility of weeds to WSMV
Increase in regional virus incidence?
Host
Pathogen Environment( New York Times)
SDSU Extension
Vector
• Determine prevalence of wheat viruses in the Great Determine prevalence of wheat viruses in the Great Plains (Plains (WSMV, HPV, TriMV, BYDV-PAV and CYDV-WSMV, HPV, TriMV, BYDV-PAV and CYDV-RPVRPV))
• Nine states: Nine states: WY, MT, CO, KS, OK, TX, SD, ND, NE
• Determine geographic distribution for TriMV & HPVDetermine geographic distribution for TriMV & HPV
• Determine if host symptoms are diagnostic among virus Determine if host symptoms are diagnostic among virus species for single and multiple infectionsspecies for single and multiple infections
• Collect and provide virus infected plant tissues to support Collect and provide virus infected plant tissues to support research effortsresearch efforts
• Increase communication about wheat viruses in the Great Increase communication about wheat viruses in the Great Plains RegionPlains Region
Wheat virus survey, 2008: Objectives
WSMVWSMV 4433
3388
4400
2288
3399
6622
2277
Range:Range: 28 – 28 – 8383
Mean:Mean: 4747
% samples infected
6611
8833
HPVHPV99
1199
1122
77
88
Range:Range: 7 - 417 - 41
Mean:Mean: 1919
% samples infected
1100
4411
3388
3300
TriMVTriMV00
2244
00
22
66Range:Range: 0 - 570 - 57
Mean:Mean: 1717
% samples infected
2277
3300
1100
5577
mixedmixed % samples infected
3377
WSMWSMV+HPV+HP
VVWSMWSM+ +
TriMVTriMVHPV+HPV+TriMVTriMV
99
88 1155
88
77
99
55
1166
0000
00
00
2211118855
2211113344
3355332288
8800
11001100
ObjectiveObjective: : Determine prevalence of wheat viruses
• WSMV detected in all GPDN states at WSMV detected in all GPDN states at high percentage infection (27 – 83 %)high percentage infection (27 – 83 %)
• HPV detected in all GPDN statesHPV detected in all GPDN states• HPV identified in MT and WY for the first HPV identified in MT and WY for the first
timetime• TriMV identified in CO, KS, NE, OK, SD, TriMV identified in CO, KS, NE, OK, SD,
TX, WYTX, WY• TriMV not detected in MT and NDTriMV not detected in MT and ND
Yield of spring wheat varieties inoculated with WSMV
0
5
10
15
20
25
30
35
Reede
r
Chote
au
Mcn
eal
Conan
Fortu
na
Ernes
t
Corbin
Hank
Amido
n
Schola
r
Yie
ld (
bu
/a)
Not inoculated
Inoculated
Race Evolution in TTKS (Ug99) Lineage
&
Implications to Resistance Breeding
Yue Jin, USDA-ARS
Ug99
First reported in Uganda in 1999 --Pretorius et al. 2000 Plant Dis
84:203 Virulent on Sr31
Sr31 is located on 1BL.1RS translocation.
Also carries Lr26, Yr9.
Increased adaptation and higher yield. As a result,
widely spread in wheat worldwide.
Helped to reduce stem rust population worldwide.
Virulence to Yr9, originated in the eastern Africa in mid 80s, caused worldwide epidemics.
TTKS
In 2002 and 2004, CIMMYT nursery planted in Njoro, Kenya were severely infected by stem rust.
In 2005, we identified Kenyan isolates from 2004 were race TTKS.
--Wanyera, Kinyua, Jin, Singh 2006 Plant Dis 90:113
Broad virulence of TTKS to North American spring wheat
US spring wheat CVs of the Northern Great Plains, known to have broad-based resistance to stem rust, were mostly susceptible (84%). 500 CIMMYT CVs released since 1950’s, 84% were susceptible.
Conclusion:
Ug99 possesses a unique virulence combination that renders many resistance genes ineffective.
Jin & Singh, 2006, Plant Dis:90:476-480
Projected potential pathways for Ug99 based on the migration of Yr9 virulence
Singh et al. 2006. CAB Review 1, 54
Ug99 migration
Singh et al. 2008. Advances in Agronomy v981998 2001?
2004
2003?2005
2006
2006
2007
Evolution of the TTKS lineage
TTKSK
TTTSKTTKST
Sr24-Sr31+Sr36-
Sr24+Sr31+Sr36-
Sr24-Sr31+Sr36+
Our data point to:
Jin et al. 2008. Plant Dis. 92:923-926Jin et al. 2009. Plant Dis. (in Press)
% of resistance to
Type Entry TTKSK TTKST TTTSK(Ug99) Sr24v Sr36v
Hard red spring 89 21% 12% 21%
Hard red winter 416 29% 15% 28%
Soft red winter 377 27% 25% 11%
Western wheat 60 3% 3% 3%
Total 942 26% 18% 19%
Ramification of Sr24/Sr36 virulence to US Wheatbased on testing of 2007 elite breeding germplasm
The good news
• Phil and Luther are both working on it already!
• Li Huang, PSPP, is starting to map genes for resistance
• Fungicide trials with great results
• Communication and education ramping up!
Wheat stem rust fungicide trial results (2008)Stein and Gupta, SDSU
Ste
m r
ust (
% le
af a
rea)
Triazoles
Triazole + Strobilurin
Fungicide modes of action: Triazoles• FRAC group 3• DMI (demethylation) inhibitors; biosynthesis of sterols in
fungal cell membrane; spore penetration and mycelial growth
• Provides 14-21 days of protection• Medium risk of resistance development• Greater mobility in plant than strobilurin fungicides• Most widely used class of fungicide in the world• Control a wide array of fungal diseases• Protective and curative effects (if applied early in disease
development)
Fungicide movement in the plant
From: Tenuta, A., D. Hershman, M. Draper and A. Dorrence. 2007. Using foliar fungicides to manage soybean rust.. Land-Grant Universities Cooperating NCERA-208 and OMAF. Available online at http://www.oardc.ohio-state.edu/SoyRust/
20 July, 2009, Fort Ellis stem rust fungicide trial (14 d after fungicide application, 45 d after pathogen inoculation)
Control
Triazole
Strobilurin
20 July, 2009, Fort Ellis stem rust fungicide trial (14 d after fungicide application, 45 d after pathogen inoculation)
Control
Strobilurin
Triazole
28 July, 2009, Fort Ellis stem rust fungicide trial (22 d after fungicide application, 53 d after pathogen inoculation)
Spreader row Triazole + Strobilurin
Fungicide modes of action: Strobilurins
• FRAC group 11• QoI (quinone outside) inhibitors (respiration); spore germination,
penetration, and mycelial growth• Provides 14-21 days of protection• High risk of resistance development because it has a very
specific mode of action (they block electron transfer at the site of quinol oxidation (the Qo site) in the cytochrome bc1 complex, thus preventing ATP formation)
• Originally isolated from wood-rotting fungi Strobilurus tenacellus• ‘Reduced-risk’ pesticide (pose less risk to human health than
other chemical options at the time of registration by EPA)• Control a wide array of fungal diseases• Excellent preventative fungicides, but limited curative effects• “Plant health benefit” independent of disease control?
Figure 1. Mobility of trifloxystrobin, an example of a QoI fungicide. http://www.apsnet.org/education/AdvancedPlantPath/Topics/Strobilurin/top.htm
Preventing fungicide resistance
• Limit the number of applications of a single FRAC group per season
• Limit the number of consecutive applications of a single FRAC group
• Mix fungicides with different modes of action (FRAC groups)
• Use early in disease development
Acknowledgements
Dai Ito, graduate studentYue Jin, UMNJeff Stein, SDSU