Title: Candidatus Liberibacter asiaticus (CLas)Titer in Field-Infected Commercial Citrus Cultivars Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 2010
Publication Date: N/A
Technical Abstract: Eight Indian River groves with four or more diverse scions planted in close proximity were surveyed. Twenty trees of each scion in each grove were randomly selected to avoid bias and edge effects and an HLB diagnostic leaf sample was collected from each. CLas 16S rDNA primers were used in qPCR, all standardized to 3 ng nucleic acid/reaction. No scion was low in CLas titer in all groves. Across all groves, 22% of the 760 trees tested had a Ct value <36 (>5.8 CLas genomes/3 ng total nucleic acid). In 2 groves there was little HLB. Data on the 6 groves with high incidence of HLB were subjected to ANOVA, focusing on divergence of CLas titer in each tree from the grove-wide mean at each location. ‘Minneola’ and ‘Murcott’ displayed the greatest CLas titer, averaging 4 to 3 X the grove averages. Sweet orange had CLas titers slightly greater than grove averages. In the lowest titer group ‘Fallglo’ and ‘Sunburst’ displayed titers averaging 0.33X grove means, while ‘Temple’ and grapefruit had titers somewhat less than 0.5X the grove means. ‘Minneola’ and ‘Temple’ differed 12 fold in CLas titer and were compared adjoining each other in all the same groves. Assessment of Las/HLB in replicated cultivar trials and breeding populations exposed to high disease pressure, and controlled psyllid challenges, have all been initiated. Since ‘Temple’, ‘Sunburst’, ‘Fallglo’ and their parents are widely used in our breeding program, we hope to identify diverse scion types with greater HLB tolerance for near-term deployment.