A Study Of Diversity And Transmission Mode Of Endophytic Bacteria In Meloidogyne Incognita

Root-knot nematode is the most dangerous plant parasitic nematode in the world,which can infect more than 3000 plants,among which Meloidogyne incognita is the most dangerous.A growing number of studies have shown that endophytic bacteria play an important role in the growth,development and reproduction of the host.However,whether the endophytic bacteria exist in M.incognita remains largely unknown.To answer this question,we used high-throughput16 S r RNA gene sequencing and pure culture methods to study the community of symbiotic bacteria in a variety of tissues in M.incognita.According to the two methods of high-throughput sequencing and pure culture,we found that Proteobacteria,Firmicutes and Bacteroidetes had the most abundant diversity at taxonomic level of phylum.The difference of diversity obtained by the two methods was the least at phylum.In the taxon of genus,the results of the two methods were significantly different.In the sample of eggs,Bacillus was the most abundant isolated by the pure culture method.Although Bacillus was also detected by high-throughput sequencing,Spingomonas and Brevundimonas were the most abundant species.In whole body of female,pure culture method showed that Enterobacteria was the most abundant,whereas the high-throughput sequencing showed that Enterobacteria,Pseudomonas and Aeromonas were the most diverse.In gonad of female adults,only Bacillus cereus,belonging to the genus Bacillus of Firmicutes,was isolated by pure culture method.Although Bacillus was also detected by high-fluence sequencing Lactobacillus and Acinetobacter were the two most abundant genera.Based on results of pure culture,we used fluorescence in situ hybridization(FISH)method to investigate the possible transmission modes of endophytic bacteria in M.incognitas.Our results showed that Bacillus cereus was transmitted vertically from the female adults to the egg through the gonadal gland.Finally,using antibiotics to remove some endophytic bacteria from the eggs,we investigated the effects of bacteria on their development and hatching.Our results showed that the removal of some endophytic bacteria from the eggs of M.incognita delayed the development of the eggs,implicating that endophytic bacteria are involved in physiolocial functions in M.incognita.In conclusion,there are endosymbiont bacteria in M.incognita,and their diversity is rich.Some of the endophytic bacteria are passed to the next generation by vertical transmission.Understanding of role for endophytic bacteria in physiological functions of M.incognita may provide a new strategy for the control of root-knot nematode.