Submitted to: International Research Conference on Huanglongbing
Publication Type: Abstract Only
Publication Acceptance Date: 1/6/2013
Publication Date: 2/1/2013
Citation: Mccollum, T.G., Hilf, M.E., Stover, E.W., Irey, M. 2013. Candidatus Liberibacter asiaticus titers in citrus cultivars in the field and in Asian citrus psyllid (ACP) inoculated greenhouse trees. 2013 International Research Conference on Huanglongbing, February 4-7, 2013, Orlando, Florida. Interpretive Summary:
Technical Abstract: A survey of seven citrus cultivars (C. sinensis, C. paradisi, ‘Temple’ tangor, ‘Minneola’ and ‘Orlando’ tangelos and, ‘Fallglo’ and ‘Sunburst’ mandarin hybrids) growing in commercial orchards in Florida revealed a correlation between visual ratings of HLB incidence and severity and CLas titer (Stover and McCollum, 2011). ‘Temple’ tangor and grapefruit consistently exhibited the least severe HLB symptoms and lowest CLas titers, followed by, in increasing order of HLB symptoms, ‘Fallglo’, C. sinensis, and ‘Minneola’. ‘Sunburst’ was an outlier in that it was rated high for HLB incidence, but had a low CLas titer. CLas titer for these same cultivars was also evaluated in a greenhouse study in which trees were exposed to free-ranging ACP and C. medica trees infected with CLas. In that study, following 315 days in the greenhouse with continuous exposure to CLas-infected source trees and ACP, the ranking of CLas titer from lowest to highest for the seven cultivars was grapefruit, C. sinensis, ‘Sunburst’, ‘Minneola’, ‘Orlando’, ‘Temple’ and ‘Fallglo’. If grapefruit and ‘Sunburst’ are eliminated from the greenhouse results there is a good agreement with results from the field. Compared to trees evaluated in the grove, trees in the greenhouse were no doubt much younger at the time of exposure to CLas-infected ACP and this may have contributed to the difference in CLas titer that were found for grapefruit and ‘Sunburst’. Based on comparison of the two data sets we conclude that exposure of young trees to CLas-infected, free-ranging ACP is a reliable method of screening for susceptibility to CLas infection.