| Biological control,as an important part of comprehensive plant disease control,has the advantages of pollution-free,pollution-free and long-term effectiveness.It is a very active research field of plant disease control at present.Actinomycetes and active substances produced to control plant diseases have been proved to be an effective measure.Although gratifying achievements have been made in the utilization of actinomycetes resources,there are still infinite resources to be exploited.Therefore,the isolation and screening of new actinomycetes with good biocontrol potential is of great significance to the research and development of biocontrol in China.In this study,136 actinomycetes were isolated from 41 soils from different vegetation types on the southern slope and the northern slope of Taibai Mountain in Qinling Mountains.The potential biocontrol actinomycetes were antagonized against pathogens and promoted plant seed germination.The rapid screening of the strains and the potted wheat and Chinese cabbage experiments were carried out to verify the growth promoting effects of the three potential strains,and the growth promoting mechanism of the three actinomycetes was also analyzed.The main findings obtained are:(1)Identification and statistics of 136 actinomycetes totaling 17 genera,including 98 strains of Streptomyces,13 strains of Nocardia,6 strains of Amycolatosis,3 strains of Bacillus licheniformis and 16 strains of other bacteria;The antagonistic activity of 136 actinomycetes was identified.67 strains of actinomycetes showed antagonistic activity against some pathogenic bacteria,but most actinomycetes had antagonistic activity against one or two pathogens,and their broad-spectrum antibacterial activity was better.Weak;for the promotion of 136 strains of actinomycetes,46 strains of actinomycetes with different gradient fermentation broth showed significant growth-promoting effects on wheat seed germination;Combined with antagonistic activity and growth-promoting,3 strains of potential biocontrol actinomycetes strains 31-1,37-23 and 25-28 with significant growth-promoting and antagonistic functions were screened.(2)The effects of 31-1,37-23 and 25-28 cell-free fermentation broth on wheat growth and mechanism were verified by wheat pot experiment.The results showed that:(1)The31-1,37-23,and 25-28 cell-free fermentation broths significantly promoted wheat plants.Treatment of wheat with 31-1,37-23 and 25-28 fermentation broth can increase the fresh quality of wheat seedlings by 37.26%~41.83%,the fresh quality of roots by38.10%~100.00%,SPAD Increased from 20.78% to 24.67%,root activity increased by2.69% to 39.06%,of which 37-23 cell-free fermentation broth was the most effective,and all indicators reached extremely significant levels;(2)Irrigation of acellular fermentation broth of three actinomycetes could increase the activities of PPO,POD,PAL and CAT defense enzymes in wheat.Among them,37-23 acellular fermentation broth had the most obvious effect.The activities of PPO,POD,PAL and CAT in wheat were significantly increased by6.67%,26.03%,45.25% and 30.88% compared with the control.(3)Three strains of actinomycete-free cell-free fermentation broth were used to significantly increase the expression levels of wheat resistance genes AOS,LOX8,auxin-related genes KO-1,GA2oX8,resistance protein genes GLU2,PR-1 and TLP.(4)Irrigation of acellular fermentation broth of three actinomycetes could improve the microbial community structure in wheat rhizosphere,increase the number of beneficial bacteria in azotobacter,sphingosinomyces and lysobacteria,and decrease the number of harmful bacteria in the genus Oyster and Microactinomycetes.(3)The growth promoting mechanism and mechanism of 31-1,37-23 and 25-28cell-free fermentation broth and microbial agents on cabbage were verified by germination test and cabbage pot experiment in cabbage.The results showed that:(1)The three cell-free fermentation broths of actinomycetes could significantly promote the growth of hypocotyls and radicles of Chinese cabbage seeds.Among them,the cell-free fermentation broth of37-23 actinomycetes had the best growth promoting effect,which made the hypocotyl length and radicle of Chinese cabbage seeds.The length increased by 42.11% and 68.02%,respectively,and the concise vitality index increased by 85.50%;(2)Three strains of actinomycetes and acellular fermentation broth could significantly improve the quality of aboveground parts and roots of Chinese cabbage,of which strain 37-23 had the best promotion effect,which significantly increased the dry weight of aboveground parts and roots of Chinese Cabbage by 39.27% and 71.13%.(3)The three cell-free fermentation broths and microbial agents could significantly improve the PPO,POD,PAL and CAT defense enzyme activities of Chinese cabbage,and the effect of bacterial treatment on the defense enzyme activity of Chinese cabbage was stronger.(4)Three strains of actinomycete cell-free fermentation broth and microbial treatment could increase the expression levels of TGA,NPR1,CTR1,AOS and PFD1.2 genes related to resistance to(SAR)and induced systemic resistance(ISR)pathways in Chinese cabbage;(5)The three cell-free fermentation broths and microbial agents could change the rhizosphere microbial community of Chinese cabbage,and there were significant differences in rhizosphere microbial communities between different treatments.The microbial community structure under the same treatment was moresimilar and identical.The similarity of microbial community structure under the treatment of strain fermentation broth and microbial agent was lower.(4)Through comprehensive identification of morphological,physiological and biochemical characteristics and molecular biology methods,strain 31-1 was identified as Streptomyces rochei,strain 37-23 as Streptomyces hokutonensis and strain 25-28 as Amycolatopsis balhimycina. |
