Study On Isolation And Screening Of Biocontrol Endophytes From Salvia Miltiorrhizae And Its Biocontrol Effects

As a new type of resource microorganisms,plant endophytes have been widely used in plant disease and insect pest control,environmental management,biological fungi,and new medicine research and development.Screening and digging out endophytic resources with agricultural value from medicinal plants has become a current research hotspot.At present,there are few reports on the biocontrol and growth promotion of Salvia miltiorrhiza endophytes.This study uses Salvia miltiorrhiza as the plant tissue Isolation and screening of endophytes were carried out,and further studies were carried out on a selected endophyte with good bacteriostatic and growth-promoting effects,revealed its systematic classification status,discussed the biological control effect and its preliminary mechanism of action,and clarified the most Optimal fermentation conditions are expected to lay a solid foundation for the development and utilization of Salvia miltiorrhiza endophytes.The main findings are as follows:82 endophytic bacteria were isolated from Salvia miltiorrhiza plant tissues by tissue separation method and dilution coating plate method,and 45 endophytic bacteria were isolated from roots(26),stems(10)and leaves(9),roots(12)and stems(18)37 strains of endophytic fungi were isolated from leaves(7).Through the plate antagonism test and seed germination test,a number of endophytic bacteria with biocontrol potential were screened out.Among them,R25 has strong antibacterial activity against a variety of tested pathogens and has broad-spectrum antagonism.It is treated with R25 fermentation broth.The germination potential of the dried Salvia seeds increased by 55.91%,the germination rate increased by 49.98%,the hypocotyl length increased by 51.04%,and the radicle length increased by 74.93%.Through the observation of the morphological characteristics of the strain R25,physiological and biochemical tests and molecular biology analysis,the strain R25 was preliminarily identified as Bacillus velezensis(Bacillus velezensis).The effects of different concentrations of R25 fermentation filtrate on the growth,spore germination and mycelial morphology of cucumber Fusarium wilt were tested,and the changes in the defensive enzyme activities in the body of cucumber plants inoculated with R25 fermentation broth were measured,and the biological control mechanism of R25 was preliminarily revealed.The results show that the strain R25 has a certain inhibitory effect on the pathogen of cucumber fusarium wilt,and obviously inhibits the growth of mycelium and the germination of spores,resulting in malformed and enlarged hyphae.The treatment of strain R25 can significantly increase the enzyme activities of POD,SOD and CAT in cucumber leaves.The fermentation filtrate of strain R25 may enhance the resistance of cucumber to Fusarium wilt by inducing systemic resistance of cucumber plants.The results of pot experiments show that the strain R25 has a significant control effect on cucumber fusarium wilt,and the control effect reaches 51.8%.The optimization of fermentation parameters clarified the most suitable culture conditions for strain R25.The best nutrient combination suitable for the growth of strain R25 is: glucose2%,yeast extract 0.5%,sodium chloride 0.75%(1L water);optimal liquid fermentation The conditions are that the optimal inoculum amount is 3%,the temperature is 32℃,the liquid is40 mL in a 150 mL shake bottle,the rotating speed of the shaker is 180 rpm,the initial p H of the medium is 7,and the optimal fermentation time is 18 hours.