Lethal and sublethal effects of vector-expressed insecticidal and antimicrobial peptides on the Asian citrus psyllid

Citrus greening disease, or huanglongbing (HLB), is a destructive disease of citrus causing reductions in fruit quality and yield. The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is one of the most economically important phloem feeding pests of citrus worldwide due to its capacity as a vector of Candidatus Liberibacter asiaticus, the bacterium thought to be the causative agent of HLB. Insecticidal control of ACP is an important aspect of HLB management; however, resistance to several insecticides has been identified in some Florida ACP populations. Transgenic plants expressing a variety of insecticidal peptides genes have been successful in increasing resistance against insect pests in a variety of agricultural crops. Two of these peptides, snowdrop lectin, Galanthus nivulis agglutinin (GNA), and indolicidin, have been found effective in food crops against phloem feeding insects; however, development of transgenic plants that express peptides is a long process. As an alternative, a citrus tristeza virus-based vector was developed to express peptides. The vector can be graft-transmitted into mature citrus, which allows for rapid screening of insecticidal peptides as novel tools for ACP control. The objective of this study was to evaluate the lethal and sublethal effects of vector-expressed GNA and indolicidin against ACP. The effect of peptides on ACP longevity, fertility and fecundity, as well as nymph development rate and survival, were determined. In addition to assessing ACP mortality and fitness, we also examined the antifeedant effect of plants containing vector-expressed peptides using choice test and honeydew excretion assays.