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棉 花 学 报 Cotton Science 2006，18(3)：131-134
Generation of Antibiosis-free Mutants of Bacillus subtilis NCD-2 with Transposon Tn917 and the Role of Antibiosis of NCD-2 in Controlling Cotton Sore Shin Abstract：The bacterial isolate NCD-2，isolated from the rhizosphere of cotton, was an effective Bacillus subtilis strain to control cotton Verticillium wilt in field. Further it had been proved that this bacterium secreted antipeptides to inhibit the plant pathogens, Verticillium dahliae of cotton Verticillium wilt and Rhizoctonia solani of cotton sore shin. This paper determined the role of the antipeptide in controlling cotton disease. A mutagenesis technique system of B. subtilis NCD-2 was generated by transposon Tn917 mutageneisis, and the functional gene encoding the antipeptide was knocked off by the transponson. In this study, B.subtilis NCD-2 was transformed with a plasmid pTV1 carrying transponson Tn917 by protoplast methods. Twenty tranformed NCD-2 strains were screened resistant against chloromycetin, erythromycin and lincomycin. By the transposon Tn917 mediated insertional mutagenesis technique, the transponson Tn917 successfully inserted the genome of B. subtilis NCD-2 and 1500 mutants were sreened that were resistant to erythromycin and lincomycin but susceptible to chloromycetin. Among them, 2 antibiosis free mutants were screened against V. dahliae . The results from the experiement on control of cotton sore shin with wild NCD-2 and antibiosis-free mutants in greenhouse showed that antibiosis of NCD-2 played an important role in controlling this disease with B.subtilis NCD-2. This suggested that the functional gene of B.subtilis NCD-2 encoding the antipeptide against V. dahliae had a significant function in control of cotton sore shin disease.
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