Using Citrus Leaf Starch Content to Predict Huanglongbing Disease with and without a Gold Standard
Abstract
Except for root tissues, healthy citrus trees accumulate very little starch, although notable starch concentrations are sporadically observed in leaves from zinc deficient trees and injured branches. However, when affected by Huanglongbing (HLB; syn. citrus greening) high levels of starch begin to accumulate throughout all aerial parts of the tree. Therefore, leaf starch content over a threshold level should indicate the presence of HLB. We conducted a comprehensive statistical analysis of a large number of leaf samples throughout the state and compared the results to PCR detection of the presumptive causing agent Candidatus Liberibacter asiaticus. Despite some general trends, the data failed to correlate minimum starch levels with PCR determination of HLB. Evaluation of the data in terms of biotic conditions surrounding HLB infection of citrus trees uncovers a sound rationalization of the observed discrepancies.
