Effect Of Associatied Bacterium From Bactrocera Cucurbitae Egg On Hosts And Their Diversity

The internal of insects is a complex micro-ecosystem,in which a large and varied microbial community inhabits.This community plays important roles in development,environmental adaptability of their host,and insect host defence against adverse factors and so on.The melon fruit fly,B.cucurbitae(Coquillett),is an important pest in vegetable and fruit crop,the adult feed on honeydew secreted by vegetable,melon and fruits,and the larva feed on rotted melon and fruit.The interactions among microorganism inhabit in insect and insect adult and larva feeding have received more and more attention by domestic and overseas researchers.The effect of associated bacterium from B.cucurbitae on insect host and host plant was studied by using bioassay method.Comparatively analyze the composition and abundance of associated bacterial population in adult ovary,egg and insect larva in loofah(Luffa cylindrica)was performed by using high-through sequencing technology based on 16 S r RNA gene sequence.Three species of bacterium were isolated from insect egg and the bacteria have the capacity of effect the development of insect from egg to larva and pupa in host plant luffa.The main results are summarized as follows:1.Effect of associated bacteria from melon fruit fly egg on host plantsThe associated bacteria from melon fruit egg significantly increased the decay of host plant loofah(Luffa cylindrica),but did not work in the host plant pumpkin(Cucurbita moschata).The area of loofah decayed in the treatment inoculated with the washing solution of associated bacteria from egg was significantly higher than that in the treatment inoculated with sterile water or solution of plant loofah washed with sterile water at time from 72 to 120 h,with no similar result in host plant pumpkin.Thes result indicated that the washing solution of melon fruit fly egg contained some essential substances that could increased the decay of host plant loofah,and didn't increased the decay of host plant pumpkin.2.Effect of associated bacteria from melon fruit fly egg on the growth and development of host larva and pupaeThe associated bacteria from fly egg could affect the development of melon fruit fly from egg to larva and pupae when insect inhabit in host plant loofah,but no effect on melon fruit fly when inhabit in host plant pumpkin.The weight of larvae or pupae of fly was significantly lower when the melon fruit fly eggs,treated by amylillin or streptomycin,grew in the host loofah compared to those in the control groups.In contrast,there were no significant difference on the weights of larvae or pupae between the treatment groups and the control when the treated melon fruit fly eggs grew in host plant pumpkin.3.Diversity analysis of associated bacterium from B.cucurbitae ovary,egg and larvaeThe result of associated bacteria sequence through high-throughput sequencing technology based on 16 S r RNA gene sequence revealed the presence of diversity on bacteria from the ovaries,fresh eggs and larvae in host loofah.The species of bacterium were similarly between the bacteria from ovary and egg,but some different in abundance of bacteria.The species and abundance of associated bacteria from larvae on loofah were different from that of ovaries and fresh eggs.At genus level,the genus including Bacillus,Klebsiella,Citrobacter,Escherichia – shigella,Enterococcus and Acinetobactor were detected in associated bacteria from insect ovary,fresh egg and larvae in loofah,however,the relative abundances of genus,Paenibacillus,Klebsiella and Citrobacter,dected in larva were significantly increased as compared to that in insect ovary and fresh egg.4.Isolation,identification and function verification of associated bacterium from B.cucurbitae eggThe associated bacteria from B.cucurbitae egg was isolated and screened,and 8strains were harvested and screened from 30 isolated colonies based on the area of rotten loofah.The bioassay of the effect of associated bacteria on loofah was performed with the mixture,target bacteria and fly egg treated with streptomycin,inoculated in host plant loofah.The bioassay results showed that the three associated bacteria,Klebsiella pneumoniae,Klebsiella aerogenes and Citrobacter freundii,increased the development of the fly from egg to larva and pupae,and increased the decay of host loofah.