Isolation And Characterization Of Endobacillus From Sugarcane And Study On The Plant Growth Promoting Mechanism

Sugarcane is the most important sugar crop in my country,and it plays an important role in promoting the increase of income and employment of farmers in the sugarcane area of our country.Guangxi is China's largest sugar-making province,with a large sugarcane planting area,many types of diseases,and serious damage.The large-scale use of chemical fertilizers and pesticides has played an important role to a certain extent,but the production costs caused by excessive application have risen and environmental pollution problems have become increasingly serious.The development and utilization of biological bacterial fertilizer provides an important guarantee for green production,quality improvement and efficiency enhancement of sugarcane.In this study,the isolation and identification of Bacillus endophyticus from sugarcane revealed the distribution of Bacillus spp.,which provided a theoretical basis for the construction of a resource library of bacillus endophytes.The main results are as follows.1.By using 16S rRNA gene sequencing,20 bacillus strains were isolated from sugarcane roots,and Rep-PCR technology was used to verify that the endobacillus has a rich phenotype and genetic diversity.2.Among the 20 strains tested,13?65%?produced IAA-like compounds in the range of 11.38-35.74?g.m L^-1 with highest amounts detected in strain Y8;10?50%?had the ability to produce siderophore;only five had the ability to solubilize phosphorus.3.Using 8 kinds of pathogenic fungi for antagonism experiments,it was found that all Bacillus spp.strains were resistant to at least one pathogenic fungus,and Bacillus velezensis Y8 had an antagonistic effect against all pathogenic fungi.4.Using Bacillus velezensis Y8 as the test strain,the fermentation process was optimized by the single factor method.The experimental results show that the following fermentation methods produce the most antibiotic extracts,this is fermentation time 36 h,inoculated bacterial volume 5%,initial p H7,fermentation temperature 28?,200 rpm.The best medium is NB.The fermentation was carried out under optimized conditions and the crude antibiotic extract produced reached 5.8 g.L^-1.5.Through thin layer chromatography,cloning of lipopeptide antibiotic synthase-related genes and UPLC-Q-TOF-MS analysis technology,it was determined that the lipopeptides secreted by the Y8 strain were surfactins,fengycins and iturins.6.The experimental results of fluorescence microscope and scanning electron microscope prove that Y8 strain has strong colonization ability in sugarcane root and leaves.The results of the growth promotion experiment showed that Bacillus velezensis Y8 could significantly promote the growth of sugarcane aboveground and underground parts of sugarcane.7.Inoculating Bacillus velezensis Y8 to sugarcane in greenhouse for biocontrol experiments,the results showed that Bacillus velezensis Y8 could reduce the incidence of sugarcane smut,indicating that it has the potential to become a biocontrol agent.