HUANGLONGBING (HLB) HOST RANGE AND

BACTERIAL SPECIES DIVERSITY

HUANGLONGBING (HLB) HOST RANGE AND

BACTERIAL SPECIES DIVERSITY

Dr. Megan DewdneyDr. Megan DewdneyAssistant Professor and Extension Assistant Professor and Extension SpecialistSpecialist

OutlineOutline1. The bacteria that cause HLB

2. Bacterial diversity in groves

3. Citrus host range of HLB

1. The bacteria that cause HLB

2. Bacterial diversity in groves

3. Citrus host range of HLB

Three Species of Bacteria Cause HLB

Three Species of Bacteria Cause HLB

• Ca. Liberibacter asiaticus– only known species in Florida

• Vectored by 2 psyllid species – Diaphorina citri and Trioza erytreae

(experimentally)

• Heat tolerant • Found on the Indian Subcontinent,

Southeast Asia, Arabian peninsula, Brazil, Louisiana and Florida

• Ca. Liberibacter asiaticus– only known species in Florida

• Vectored by 2 psyllid species – Diaphorina citri and Trioza erytreae

(experimentally)

• Heat tolerant • Found on the Indian Subcontinent,

Southeast Asia, Arabian peninsula, Brazil, Louisiana and Florida

• Has not been found in Florida

• Vectored by 2 psyllid species– Trioza erytreae and Diaphorina citri

(experimentally)

• Bacterium and vector heat sensitive• Found in many African countries,

Madagascar and Yemen at higher altitudes

• Has not been found in Florida

• Vectored by 2 psyllid species– Trioza erytreae and Diaphorina citri

(experimentally)

• Bacterium and vector heat sensitive• Found in many African countries,

Madagascar and Yemen at higher altitudes

Ca. Liberibacter africanus

Ca. Liberibacter africanus

Ca. Liberibacter americanus

Ca. Liberibacter americanus

• Newest species of bacteria that cause HLB– Not found in Florida

• Vectored by Diaphorina citri• Disease is not as severe as when caused

by Asian species• Heat tolerant• Only found in Brazil currently• Is not found in citrus as often as in the past

• Newest species of bacteria that cause HLB– Not found in Florida

• Vectored by Diaphorina citri• Disease is not as severe as when caused

by Asian species• Heat tolerant• Only found in Brazil currently• Is not found in citrus as often as in the past

New Disease of Potato –Zebra Chip

New Disease of Potato –Zebra Chip

• Caused by a newly identified Ca. Liberibacter– Identified in New Zealand

• Vectored by the potato/tomato psyllid – Bactericera cockerelli

• Also damages tomatoes and peppers• From South Texas to Colorado as well as

Mexico, Guatemala

• Caused by a newly identified Ca. Liberibacter– Identified in New Zealand

• Vectored by the potato/tomato psyllid – Bactericera cockerelli

• Also damages tomatoes and peppers• From South Texas to Colorado as well as

Mexico, Guatemala

Bacterial Diversity StudyBacterial Diversity Study

Asymptomatic Asymptomatic grovegrove

HLB infected HLB infected grovegrove

177 177 samplessamples

186 186 samplessamples

PhylumPhylum ClassClass OrderOrder Order Order %%

ProteobacterProteobacteriaia

αα - - proteobacteriaproteobacteria

RhizobialesRhizobiales 91.591.5

UnclassifiedUnclassified 4.54.5γγ - -

proteobacteriaproteobacteriaEnterobacteriaEnterobacteria

lesles1.1 1.1

BacteroideteBacteroidetess

UnclassifiedUnclassified UnclassifiedUnclassified 5.65.6

FirmicutesFirmicutes BacilliBacilli BacillialesBacilliales 0.50.5

Bacterial Diversity StudyBacterial Diversity StudySymptomatic GrovesSymptomatic Groves

ProteobacteriaProteobacteria αα – – proteobacteriaproteobacteria RhizobialesRhizobiales91.5 %91.5 %

CaCa. Liberibacter spp. are with in . Liberibacter spp. are with in the Rhizobialesthe Rhizobiales

PhylumPhylum ClassClass OrderOrder Order Order %%

Proteobacteria α - proteobacteria

Rhizobiales 29

Unclassified 3.2β -

proteobacteriaBurkholderiales 15.6

γ - proteobacteria

Pseudomonodales

Xanthomonadales

5.9

Unclassified Unclassified 0.5Bacteroidetes Unclassified Unclassified 43.0Actinobacteria Actinobacteria Actinomycetales 0.5

Deinococcusthermus

Deinococci Deinococcales 2.2

Bacterial Diversity StudyBacterial Diversity StudyAsymptomatic GrovesAsymptomatic Groves

ProteobacteriaProteobacteria αα – – proteobacteriaproteobacteria Rhizobiales Rhizobiales 29 % 29 %

Future DirectionsFuture DirectionsTo look at bacterial populations before and after infection in:•Psyllids•Dodder•Periwinckle•Tobacco

To look at bacterial populations before and after infection in:•Psyllids•Dodder•Periwinckle•Tobacco

AsymptomaAsymptomatictic

grovegrove

HLB HLB infectedinfected grovegrove

Bacterial diversity of roots from both asymptomatic and HLB infected groves

Bacterial diversity of roots from both asymptomatic and HLB infected groves

HOST RANGE HOST RANGE EXPERIMENTSEXPERIMENTS

Questionable whether resistance occurs in Questionable whether resistance occurs in Citrus Citrus speciesspecies and relativesand relatives

Lots of ‘tolerance’ in greenhouse, but plants Lots of ‘tolerance’ in greenhouse, but plants eventually dieeventually die

Even if tolerant citrus species are found, Even if tolerant citrus species are found, tolerance tolerance cannot be moved into commercial cannot be moved into commercial scions by scions by conventional breedingconventional breeding

Citrus varieties and relatives that have been inoculated

Citrus varieties and relatives that have been inoculated

11 CitrusCitrus macrophyllamacrophylla (Alemow)(Alemow)

22 Valencia Sweet OrangeValencia Sweet Orange33 Flame GrapefruitFlame Grapefruit44 Nules clementine Nules clementine

(mandarin)(mandarin)55 Minneola TangeloMinneola Tangelo66 Eureka lemonEureka lemon77 Volkamer LemonVolkamer Lemon88 Persian limePersian lime99 Mexican limeMexican lime1010 CitronCitron1111 CarrizoCarrizo1212 PoncirusPoncirus trifoliatatrifoliata1313 CitrusCitrus halimiihalimii1414 CitrusCitrus indicaindica1515 CitrusCitrus micanthramicanthra var. var.

microcarpamicrocarpa1616 CitrusCitrus ambyllocarpaambyllocarpa

11 CitrusCitrus macrophyllamacrophylla (Alemow)(Alemow)

22 Valencia Sweet OrangeValencia Sweet Orange33 Flame GrapefruitFlame Grapefruit44 Nules clementine Nules clementine

(mandarin)(mandarin)55 Minneola TangeloMinneola Tangelo66 Eureka lemonEureka lemon77 Volkamer LemonVolkamer Lemon88 Persian limePersian lime99 Mexican limeMexican lime1010 CitronCitron1111 CarrizoCarrizo1212 PoncirusPoncirus trifoliatatrifoliata1313 CitrusCitrus halimiihalimii1414 CitrusCitrus indicaindica1515 CitrusCitrus micanthramicanthra var. var.

microcarpamicrocarpa1616 CitrusCitrus ambyllocarpaambyllocarpa

17 Sour orange18 Meiwa kumquat19 Khalily20 Citrus hystrix21 Swingle citrumelo22 Sun Chu Sha (mandarin)23 Palestine Sweet lime24 Murraya paniculata25 Citrus latipes26 Cleopatra mandarin27 Madam Vinous Sweet

Orange28 Duncan grapefruit29 Ling Ping Yau pummelo30 Hirado Buntan Pink

pummelo31 Siamese Sweet pummelo32 Severinia buxifolia

17 Sour orange18 Meiwa kumquat19 Khalily20 Citrus hystrix21 Swingle citrumelo22 Sun Chu Sha (mandarin)23 Palestine Sweet lime24 Murraya paniculata25 Citrus latipes26 Cleopatra mandarin27 Madam Vinous Sweet

Orange28 Duncan grapefruit29 Ling Ping Yau pummelo30 Hirado Buntan Pink

pummelo31 Siamese Sweet pummelo32 Severinia buxifolia

Healthy Infected Healthy Infected Healthy Infected

• Research ResultsResearch Results– No citrus cultivar or relative found to be No citrus cultivar or relative found to be

resistant to HLBresistant to HLB– Some cultivars more tolerant to HLBSome cultivars more tolerant to HLB– Symptoms less severeSymptoms less severe

Cleopatra mandarinCleopatra mandarin Citrus macrophyllaCitrus macrophylla Persian lime Persian lime

+++ +++ +++Relative number of Ca. Liberibacter cells

CitrusCitrus latipeslatipes++

Mexican LimeMexican Lime++++++

Sun Chu Sha (mandarin)Sun Chu Sha (mandarin)++++++

Volkamer LemonVolkamer Lemon++++++

Valencia Sweet OrangeValencia Sweet Orange++++++

Khalily/CarrizoKhalily/Carrizo

Flame GrapefruitFlame Grapefruit++++

ConclusionsConclusions• 3 species of Ca. Liberibacter are

thought to cause HLB• Only one species is found in Florida• There is good association between

symptoms and Ca. Liberibacter spp.• Citrus species vary in their symptoms

of HLB• The severity of symptoms is not always

associated with the number of Ca. Liberibacter in a plant

• 3 species of Ca. Liberibacter are thought to cause HLB

• Only one species is found in Florida• There is good association between

symptoms and Ca. Liberibacter spp.• Citrus species vary in their symptoms

of HLB• The severity of symptoms is not always

associated with the number of Ca. Liberibacter in a plant

Citrus Research and Education Center

Citrus Research and Education Center

Dr. Ron Brlansky Dr. William Dawson

Dr. Nian Wang

Dr. Ron Brlansky Dr. William Dawson

Dr. Nian Wang