Abstract:

Endophytes are important biocontrol resources in controlling plant diseases. The Pseudomonas putida HB3S-20 was screened as a potential biocontrol agent which had significant control effect against cotton Verticillum wilt in our laboratory. The colonization dynamics and colonization sites of strain HB3S-20 incotton tissues were detected using rifampicin resistance labeling technique and GFP labeling technique in this study. Moreover, the activities of the plant defense-related enzymes SOD, POD and CAT of cotton after inoculation of the strain HB3S-20 were detected. The rifampicin resistance labeling experiment showed that the strain HB3S-20 mainly colonized the roots of cotton, the amount of bacteria of the strain HB3S-20 detected in cotton roots ranged from 2.2×10⁴ to 6.7×10⁴ cfu/g on the 3^rd to 30^th day after inoculation of the strain HB3S-20. The amount of bacteria of the strain HB3S-20 detected in cotton stems ranged from 0.04×10⁴ to 2.7×10⁴ cfu/g, lower than the amount of bacteria in roots, but not found in leaves. The results of GFP labeling experiment showed that the strain HB3S-20 not only attached to the surface of cotton roots but also colonized the vascular system of cotton roots. Moreover, the strain HB3S-20 could increase the activities of the plant defense-related enzymes SOD and POD in cotton, and it indicated that the strain HB3S-20 could induce systemic resistance and enhance the resistance of cotton to the pathogens. In this research, the colonization regulation and induced resistance of Pseudomonas putida HB3S-20 incotton were studied, which provides theoretical basis for the mechanism of the strain HB3S-20 controlling cotton Verticillium wilt.

Key words: Pseudomonas putida, cotton, colonization; induced resistance