Factors influencing transmission of the huanglongbing (greening) pathogen by the Asian citrus psyllid and methods for interrupting the transmission process

Understanding the interaction between the Asian citrus psyllid (ACP), Diaphorina citri and the causal pathogen of huanglongbing (HLB), Candidatus Liberibacter asiaticus (Las), is critical to managing the spread of HLB. We have recently examined a suite of parameters that govern Las transmission and several important factors have emerged that may modulate transmission by ACP and serve as targets for breaking the cycle of transmission. Our recent findings indicate that Las transmission is temperature-dependent. Previous investigations suggest that up-regulation of proteins during cold acclimatization may influence insect responses to pathogens; therefore, we propose to determine how temperature-mediated gene expression influences Las transmission. In addition, our recent results suggest that Wolbachia, a psyllid symbiont, differentially infects ACP populations, and psyllids are less likely to harbor Las when Wolbachia is present. We propose to investigate this interaction by creating Wolbachia-infected and uninfected ACP colonies using microinjections to artificially infect ACP. Subsequently, we will evaluate the effects of Wolbachia on transmission efficiency by ACP and the effects of this ACP symbiont on replication of Las, ACP fitness, and immune gene expression. We anticipate identification of temperature-related factors that may inhibit the Las transmission process. We also anticipate identification of Wolbochia strains that inhibit transmission of Las by ACP. Our overall goal is to determine whether we can create ACP that are non-competent vectors of Las by manipulating populations of their bacterial symbionts (Wolbachia). The eventual practical outcome of these investigations would be to release ACP into natural populations that harbor these transmission-interfering Wolbachia, such that they would become established in natural psyllid populations, inhibiting the psyllids’ capability for vectoring the HLB pathogen. Defining temperature-mediated underlying mechanisms that facilitate Las transmission will identify weak links that may be exploited for interrupting the transmission process in the field.