The colonization of endophytic Bacillus velezensis BHZ-29 in cotton enhances defence enzyme activities against cotton Verticillium wilt

Abstract In order to clarify the colonization characteristics and induced disease resistance of endophytic bacteria against Verticillium dahliae , the colonization ability in cotton and the defence enzyme activities of cotton were determined by using the antibiotic labeling method and the greenhouse pot culture method, respectively. The results showed that there was no significant difference in morphological characteristics, antagonistic ability and disease prevention effect between RIF-resistant strains and original strains. The colonization experiment showed that BHZ-29 could be effectively colonized in the roots, stems and leaves of the three varieties of cotton, and the colonization ability was ranked as root > stem > leaf. The colonization dynamics of B. velezensis BHZ-29 in different resistant varieties of cotton showed that the maximum colonization amount of root was 9.13 × 10 5 CFU/g for Xinluzao 61T, 1.82 × 10 5 CFU/g for 9T, and 1.30 × 10 5 CFU/g for Xinluzao 36S. The activities of defense enzymes among three varieties of cotton showed an initial increasing trend after which it decreased, ranked in the following order: BHZ-29 + VD > BHZ-29 > CK > VD. The highest Vc content of Xinluzao 36S inoculated with BHZ-29 + VD was 2281.12 µg/g ·FW, Xinluzao 61T inoculated with BHZ-29 was 2278.30 µg/g·FW, 9T inoculated with BHZ-29 + VD was 2268.43 µg/g FW. The order of MDA content in the three varieties was VD > CK > BHZ-29 > BHZ-29 + VD.