Molecular survey and phylogenetic relationship of endosymbionts in diaphorina citri from hlb-infected citrus suhuiensis and hlb-free murraya paniculata / Nurul Fithriah Md Amin

Diaphorina citri is the psyllid vector of Candidatus Liberibacter asiaticus (Ca. Li. asiaticus), the causative agent of Huanglongbing (HLB), a debilitating citrus disease. Known to also feed on other host plants without causing any HLB symptoms, this psyllid also harbours other endosymbionts namely Syncytium, Mycetocyte, Wolbachia sp. and Arsenophonus sp. However, it is not certain whether Candidatus Liberibacter asiaticus and these other endosymbionts are obligate or transient endosymbionts or whether their presence is influenced by the disease status of the host plants or type of host plants the psyllid feeds on. Thus the aims of this study were to detect the presence of Ca. Li. asiaticus, Syncytium, Mycetocyte, Wolbachia sp. and, Arsenophonus sp. in Diaphorina citri, from HLB-infected Citrus suhuiensis and HLB-free Murraya paniculata and to determine the nucleotide variation and hence the phylogenetic relationship of each type of the endosymbionts of Diaphorina citri from HLB-infected and HLB-free plants. Detection of Mycetocyte, Syncytium, Arsenophonus sp. and Ca. Li. asiaticus endosymbionts was carried out by amplifying the partial 16S rDNA genes whereas detection of Wolbachia sp. was carried out by amplifying the wsp gene. Phylogenetic trees were constructed using Neighbour-Joining method. This study showed that Mycetocyte, Syncytium, Wolbachia sp., and Arsenophonus sp. are present in at least 66.7 % and 62.5% of the pysllid population feeding on Citrus suhuiensis and Murraya paniculata respectively. Thus they are transient rather than obligate endosymbionts. Their presence is also not influenced by the disease status and type of host plants the psyllids feed on. Ca. Li. asiaticus however, are only found in psyllids feeding on HLB-infected Citrus suhuiensis. Thus, their presence is influenced by the disease status of the host plants. Sequence analyses of the five endosymbionts from both HLB-infected and HLB-free plants revealed 14 haplotypes each with its own accession number. There is only one haplotype for Ca. Li. asiaticus and two haplotypes for Syncytium and Wolbachia. In Mycetocyte and Arsenophonus there are three and six haplotypes respectively. Phylogenetic analyses based on the partial 16S rDNA genes and wsp genes showed that there are no significant genetic variations or evolutionary changes between the endosymbionts of Diaphorina citri feeding on HLB-infected Citrus suhuiensis and Murraya paniculata. The data obtained from this study are the first on the prevalence of diversity and phylogenetic relationship endosymbionts in Diaphorina citri from HLB infected Citrus suhuiensis and HLB free Murraya paniculata.