Colonization Dynamics Of Endophytic Bacteria BS-41 In Soybean And Isolation And Screening Of Beneficial Endophytic Bacteria In Soybean

Endophytic bacteria can produce substances with antibacterial and growth-promoting properties,which can not only inhibit the infection of plant pathogens to host plants,but also promote the growth of plants.They are important microbial resources.In this study,soybean endophytic bacteria were taken as the research object,which laid a theoretical foundation for the application of plant endophytic bacteria.In order to study the colonization stability of soybean endophytic bacteria BS-41 with antagonistic ability during the whole growth period of soybean plants and to test whether endophytic bacteria can be inherited through seeds to the next generation,the mutant strain BS-41 R resistant to rifampicin was induced by using antibiotic labeling method in this experiment.Two soybean varieties Zhonghuang 13 and L85-2352 were treated with root irrigation for 4,8,16,32,52 and 92 days later,the content of BS-41R in soybean roots,stems,leaves,flowers and pods was detected by plate separation method,and then the newly harvested soybean seeds were re-sown.The colonization of BS-41R was separated and detected again,and the related biological characteristics of newly harvested soybean seeds were tested.The results showed that strain BS-41 R could colonize in two soybean varieties Zhonghuang 13 and L85-2352 stably,and the number of colonization was different in different parts.The colonization in roots was generally higher than that in stems,leaves,flowers and pods.BS-41R could also be detected in re-sown soybean plants.The results showed that BS-41 R could colonize stably in soybean and inherit to the next generation through seeds.The newly harvested soybean showed certain resistance to Phytophthora sojae.The above research laid a theoretical foundation for the production and application of BS-41 R.In order to isolate and screen endophytic antagonistic bacteria in soybean,tissue homogenate method was used to isolate endophytic bacteria from soybean plants infected with Phytophthora sojae P6497 and soybean plants not infected with P.sojae P6497.The 16S rDNA and gyrB sequence analysis were used to identify the isolated endophytic bacteria.At the same time,the antagonistic strains against P.sojae were screened by plate confrontation method,and the induced and promoting effects and colonization ability of endophytic antagonistic bacteria were determined.The results showed that 112 endophytic bacteria were isolated from the two soybean materials,22 of which could antagonize P.sojae P6497,with the highest inhibition rate of 56%.Soybean inoculated with endophytic antagonistic bacteria has improved in germination rate,plant height,root length and dry weight.The labeled strains can be recovered after 4,8,16 and 32 days of root irrigation with labeled strains induced by antibiotics.The maximum recovery amount can reach 233 X 102cfu/g.The soybean yellow seedlings inoculated with endophytic bacteria are resistant to P.sojae S34.The results showed that the selected endophytic antagonistic bacteria had certain promoting effect on soybean and could colonize stably in soybean.The colonization dynamics of BS-41R in other soybean varieties were also tested.It was found that BS-41R could colonize in seven different soybean varieties.Meanwhile,the difference of endophytic bacteria in different soybean plants was analyzed by high-throughput sequencing method,which provided a new idea and method for the research of endophytic bacteria.