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Title: Variables in screening for resistance to Huanglongbing

Author
item Stover, Eddie
item MOORE, GLORIA - University Of Florida
item GROSSER, JUDE - University Of Florida
item BRLANSKY, RON - University Of Florida
item GRUBER, BARRETT - University Of Florida
item Shatters, Robert - Bob

Submitted to: International Research Conference on Huanglongbing
Publication Type: Abstract Only
Publication Acceptance Date: 10/20/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: A series of experiments were initiated to assess factors which might permit more rapid screening for huanglongbing (HLB) resistance, using sweet orange in all experiments and Carrizo and/or Temple as sources of resistance/tolerance. Numerous researchers working on huanglongbing provided observations to identify study components. Consistency of Candidatus Liberibacter Asiaticus (CLas) titer and effectiveness in infecting target trees was evaluated using several source genotypes for graft inoculations: rough lemon and Valencia were much better sources of graft inoculum than citron or Volk, even though citron had very high titer levels. Effect of continuous vs. diurnal lighting was assessed in factorial with scoring (to enhance starch accumulation) on symptom severity and rapidity: continuous light accelerated symptom development but scoring did not. Effect of oscillating stress on symptom development was assessed with inconsistent results. Levels of dead vs living Candidatus Liberibacter asiaticus were assessed in inoculum source budwood and levels of dead Candidatus Liberibacter asiaticus were never more than 50 percent, suggesting likelihood of little effect. Effect of feeding source genotype was assessed on inoculativity of Asian citrus psyllid (ACP): no major differences were observed. Several additional experiments will be completed before February 2015: inoculation by grafting vs. two weeks of no-choice hot psyllid feeding vs. continuous choice hot psyllid inoculation; effect of diverse (identified through sequencing) Florida Candidatus Liberibacter asiaticus strains on response of generally susceptible vs. resistant/tolerant citrus cultivars; and effect of rootstock (including several reported to confer resistance) on Candidatus Liberibacter asiaticus titer and huanglongbing symptoms. Consistent rapid screening is critical to efficiently assess disease resistance among plant materials. Despite the rapidity of huanglongbing (HLB) spread in Florida, it often takes 8-10 months to observe a high level of Candidatus Liberibacter asiaticus infection even in highly susceptible sweet orange. The observations from these experiments should increase efficiency in screening for huanglongbing resistance and may contribute to more uniform testing between labs.