Insect Science

AbstractThe incidence of a bacterium “Candidatus Liberibacter asiaticus” was assessed in a Florida population of Asian citrus psyllid, Diaphorina citri. The bacterium is the presumed causal agent of Asiatic huanglongbing, a serious citrus disease. Adult D. citri were periodically collected between May 2010 and September 2012 in a block of diseased trees located in east‐central Florida. The psyllids were individually subjected to molecular analyses (quantitative polymerase chain reaction assays using HLBaspr primers) to determine whether the bacterium was present and, if so, the population level of the pathogen based on qPCR cycle threshold (CT) values. Significantly greater percentages of females tested positive for the pathogen than males, but there were no significant differences between females and males with respect to population levels of the pathogen within the psyllids. No significant differences were found among the three D. citri colour morphs with respect to percentages of adults testing positive for the pathogen. Among 47 sample dates, a mean of 17.5% of adults per sample date tested positive (CT < 36) for the pathogen with a mean CT value of 31.1. The incidence of the pathogen was generally higher during late fall or early winter and often lower during mid‐ to late summer. There was a significant negative correlation between percentages of D. citri testing positive and air temperature. Increases in the incidence of the pathogen may not necessarily correspond to increases in transmission, as a number of factors both internal and external to D. citri can influence transmission. Transmission rates may be highest during periods when D. citri infestation levels are large, a high percentage of adults carry a high population of the pathogen in their salivary glands, and citrus flush is abundant.

Abstract Asian citrus psyllid D iaphorina citri is the vector of the citrus H uanglongbing ( HLB ) associated bacterial agent ‘ C andidatus L iberibacter asiaticus’ ( C L as). The molecular interactions between C L as and D . citri remain unclear. In the present study, protein profiles of mitochondrial, microsomal and cytosolic fractions from uninfected and C Las‐infected adult D . citri are investigated using two‐dimensional gel electrophoresis. The comparative analysis reveals a total of 18, 24 and 20 protein spots that are unique or differentially expressed in mitochondrial, microsomal and cytosolic proteins fractions respectively. These proteins are successfully identified by mass spectrometry. Among the 62 identified proteins, 30 are up‐regulated, whereas 32 are down‐regulated. These proteins include important components in energy metabolism such as ATP synthase, ATP ase, ATP / ADP carrier protein, etc.; host stress responses such as heat shock proteins; host detoxification processes (i.e., cytochrome P 450 and glutathione S ‐transferase); and the cytoskeleton (such as actin, tubulin, myosin and tropomyosin). These data suggest that, after C L as infection, several proteins of D . citri , especially energy metabolism and protein biosynthesis, are altered, and extensive host defence responses are induced. In conclusion, the present study reports proteomic information that is helpful in understanding the vector–pathogen relationship between C L as and D . citri , and could be used to identify potential targets for limiting the spread of C L as, as well as to provide new insights into HLB management.