Abstract
The Asian citrus psyllid (Diaphorina citri Kuwayama) is an insect pest capable of transmitting Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus greening in North America. D. citri also harbors three endosymbionts, Wolbachia, Candidatus Carsonella ruddii, and Candidatus Profftella armatura, which may influence D. citri physiology and fitness. Although genomic researches on these bacteria have been conducted, much remains unclear regarding their ecology and inter-population variability in D. citri. The present work examined the densities of each endosymbiont in adult D. citri sampled from different populations using quantitative PCR. Under field conditions, the densities of all three endosymbionts positively correlated with each other, and they are associated with D. citri gender and locality. In addition, the infection density of CLas also varied across populations. Although an analysis pooling D. citri from different populations showed that CLas-infected individuals tended to have lower endosymbiont densities compared to uninfected individuals, the difference was not significant when the population was included as a factor in the analysis, suggesting that other population-specific factors may have stronger effects on endosymbiont densities. To determine whether there is a genetic basis to the density differences, endosymbiont densities between aged CLas-negative females of two D. citri populations reared under standardized laboratory conditions were compared. Results suggested that inter-population variability in Wolbachia infection density is associated with the genotypes of the endosymbiont or the host. Findings from this work could facilitate understanding of D. citri-bacterial associations that may benefit the development of approaches for managing citrus greening, such as prevention of CLas transmission.Electronic supplementary materialThe online version of this article (doi:10.1007/s00248-016-0733-9) contains supplementary material, which is available to authorized users.
Highlights
Bacterial endosymbionts of insects can profoundly influence their host’s biology [1,2,3]
Characterizing factors associated with infection densities of D. citri endosymbionts is a necessary step for understanding these bacteria’s influence on the psyllid host
Using quantitative real-time polymerase chain reaction (qPCR) and absolute quantitation methods, the present study investigated the ecology of D. citri endosymbionts across different field populations
Summary
Bacterial endosymbionts of insects can profoundly influence their host’s biology [1,2,3]. Some bacteria provide nutritional or protective benefits to the host, while others can affect an insect vector’s efficiency in transmitting viruses [4,5,6,7,8]. Such findings suggest that insect-microbe associations may be exploited for managing insect pests or insect-transmitted diseases. Citrus greening is a destructive plant disease caused by the Alphaproteobacterium Candidatus Liberibacter asiaticus (CLas) and other closely related species [9,10,11,12]. The Asian citrus psyllid (Diaphorina citri Kuwayama) transmits CLas in North America, Asia, and Brazil [10]. Thereafter, the pathogen may cross the gut barrier and invade the salivary gland, thereby enabling D. citri to transmit the pathogen to another plant
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