关键词: 芽孢杆菌HT-7, 棉花黄萎病, 大丽轮枝菌, 拮抗作用, 生物防治

Abstract: The prupose of this study was to obtain safe,efficient and sustainable biological control resources of Verticillium wilt of cotton,explore the main antagonistic factors,and carry out green prevention of Verticillium wilt of cotton.Bacillus sp.HT-7,a strain with good control effect on Verticillium wilt of cotton was isolated from the root soil of Verticillium wilt resistant cotton(Hai 7124).Plate confrontation method and pot experiment were used to explore the disease resistance of the antagonistic strain,and the antagonistic factors were explored by ammonium sulfate salting out and gene cloning for antibacterial identification.The plate confrontation experiment showed that the inhibition rate of HT-7 on the pathogen of V.dahliae was 56%.Pot experiments showed that HT-7 strain could significantly improve the resistance of upland cotton to Verticillium wilt.Compared with the control group,the cotton roots treated with strain HT-7 had a cure effect of 82.58% after inoculated with V.dahliae.Further studies indicated that HT-7 fermentation broth could significantly inhibit the spore germination of V.dahliae.It was identified that the main antagonistic factor in strain HT-7 was protein substance β-1,3-1,4-glucanase.The β-1,3-1,4-glucanase gene was cloned from HT-7 and highly expressed in E.coli BL21.The purified recombinant enzyme could obviously inhibit the growth of V.dahliae with a bacteriostatic rate of 25% and had an activity
of 23.5 U/mL.In summary,an antagonistic Bacillus sp.HT-7 was successfully isolated and β-1,3-1,4-glucanase was an important virulence factor in HT-7,which laid a foundation for the further development of biological control strains of Verticillium wilt in cotton.

Key words: Bacillus sp.HT-7, Verticillium wilt of cotton, V.dahliae, Antagonism, Biological control