The Diversity Of Predominat Endosymbionts Of Bemisia Tabaci(Hemiptera: Gennadaius) And Its Function On Itself And Dominant Parasitoid

Inherited intracellular insect endosymbionts may manipulate host reproduction or provide fitness benefits to their hosts in ways that result in their spread throughout a host population. The whitefly Bemisia tabaci(Gennadius) harbours the primary endosymbiont Candidatus Portiera aleyrodidarum and seven genera/species secondary endosymbionts. The primary endosymbiont to provide essential nutrients for development and reproduction of host, but the secondary endosymbionts can enhance the adaptability of the host to the environmental conditions, increase the resistance to natural enemies as well as enhance the susceptibility of the host to insecticides. Firstly, we used molecular methods to analyse the diversity and distribution of the endosymbiont symbiotics of B. tabaci MEAM1 and MED cryptic species and three dominant parasitoids. Depending on specific 16 S rRNA Rickettsia and Hamiltonella gene sequences, Bayesian inference(BI) phylogenetic tree were constructed to analysis the phylogenetic relationships; Secondly, we compared the differences of life history traits of B. tabaci MED after feeding on two antibiotics(rifampicin and tetracycline); Lastly, we evaluated how resident endosymbionts of Bemisia tabaci modeulate the life history traits of Eretmocerus hayati. The main results were as follows:(1) The diversity and abundance of endosymbionts of two mainly invasive whiteflies and its dominant parasitoids were quite different. The symbiotic abundance of B. tabaci MEAM1 and MED was greater than those of the three dominant parasitoids. Two cryptic whiteflies harboured Portiera, Hamiltonella and Rickettsia; Among three dominant parasitoids, the diversity and abundance of endosymbionts in Encarsia formosa was highest, which harboured Rickettsia, Hamiltonella and Wolbachia. But, Encarsia Sophia and Er. hayati only harboured Rickettsia. There are 4 types of endosymbionts in whiteflies and its three dominant parasitoids, which belong to the Proteobacteria, α‐Proteobacteria and γ‐Proteobacteria. The Bayesian analysis based on 27 unique 16 S rRNA genes of Rickettsia showed that the Rickettsia in B. tabaci MEAM1 and MED and its three dominant parasitoids were clustered together, with a closer genetic relationship, and all belong to Rickettsia bellii group. It suggested that Rickettsia could occur horizontal transmission between whiteflies and parasitoids. The phylogenetic tree of Hamiltonella showed similar results.(2) Feeding on antibiotic had negative effects on host fitness of B. tabaci MED. When the same concentration of two antibiotics were supplied, fecundity, offspring sex ratio, emergent number and hatch number of B.tabaci were significant reduced respectively. When comparing the effects feeding on three different concentrations of rifampicin, the emergence rate and hatch rate of B. tabaci were significantly reduced. The similar results had been found on tetracycline. However, the offspring sex ratio, emergent number and hatch number of B.tabaci feeding on the same antibiotic with different concentrations had no significant difference. Relative to the control, the longevity, fecundity, and hatch rate of B. tabaci feeding on two antibiotics were quite differences. In contrast, rifampin produced a stronger negative effect on B. tabaci life history traits, which may be due to high eliminated efficiency on endosymbiotic bacteria of rifampin.(3) Er. hayati. showed quite different life history traits when B. tabaci harboured different endosymbionts. Firstly, the durations of nymphal stage and pupal stage and immature stage of female and male of Er. hayati were significant different. The nymphal duration of RH-free treatment was the longest, RH-plus treatment in mediate, H-plus treatment in the shortest; And pupal stage and longevity showed similar results, the development time of RH-free is the longest, RH-plus and H-plus treatment followed; The development time of each stage in male also showed similar results. Secondly, the biocontrol efficiencies(host feeding, fecundity, total mortality) of Er. hayati were also quite different among different treatments, those of RH-free treatment was the highest; But RH-free and H-plus treatment were higher than RH-plus treatment of female longevity. Thirdly, the emergence rate of parasitoids in the RH-plus and H-plus treatments were significant higher than those in RH-free treatment. However, the emergence number and sex ratio among the three treatments had no significant difference. Besides, the daily biocontrol efficiencies were affected by different treatments. In conclusion, B. tabaci MED harbouring different endosymbionts could affect the life history traits of Er. hayati. It seems that the endosymbiont could protect B. tabaci from the attack of Er. hayati.