Professor University of Florida Lake Alfred, Florida
The inability to culture ‘Candidatus Liberibacter asiaticus’ (CLas) in vitro remains a significant limitation in citrus greening disease (Huanglongbing, HLB) research, hindering efforts to develop a cure. A major focus of ongoing research is understanding the transmission dynamics of CLas by its insect vector, Diaphorina citri. To revisit key transmission parameters, we recently established novel techniques, including in vitro D. citri egg hatching and topical feeding of nymphs. Following surface sterilization of D. citri eggs, we used the egg-hatching medium to demonstrate the absence of transovarial transmission of CLas. Our findings indicate that acquisition of CLas occurs at the third nymphal instar or later. CLas DNA could not be detected in eggs or the first two instars, while its titer positively correlated with developmental progression from the fourth instar to the adult stage. Additionally, we utilized Bergera koenigii (curry leaf tree), a CLas-immune host plant, to study pathogen retention in adult insects. When CLas-infected D. citri adults were reared on B. koenigii, a gradual decline in CLas titer was observed, suggesting that the bacterium does not replicate within the adult insect on a non-host plant. These findings contribute to a deeper understanding of vector-pathogen interactions and may inform more effective control strategies against citrus greening disease.
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