title: Screening of high-yielding biocontrol bacterium Bs-916 mutant by ion implantation.
abstract: Bacillus subtilis 916 was an effective biocontrol agent in control rice sheath blight caused by Rhizoctonia solani. To further improve its antagonistic ability, low-energy ion implantation was applied in Bs-916. We studied the effects of different doses of N(+) implantation. The optimum dose of ion implantation for the Bs-916 was from 15 x 2.6 x 10(14) N(+)/cm(2) to 25 x 2.6 x 10(14) N(+)/cm(2). The mutant strain designated as Bs-H74 was obtained, which showed higher inhibition activity in the screening plate. Its inhibition zone against the indicator organism increased by 30.7% compared to the parental strain. The control effect of rice sheath blight was improved by 14.6% over that of Bs-916. Thin-layer chromatography and high-performance liquid chromatography analysis indicated that lipopeptides produced by Bs-916 and the mutant strains belonged to the surfactin family. Bs-H74 produced approximately 3.0-fold surfactin compared to that of Bs-916. To determine the role of surfactin in biocontrol by Bs-916, we tested another mutant strain, Bs-M49, which produced lower levels of surfactin significantly, and found that Bs-M49 had no obvious effects against R. solani. These results suggested that the surfactin produced by Bs-916 plays an important role in the suppression of sheath blight. These observations also showed that the Bs-H74 mutant strain is a better biocontrol agent than the parental strain.
authors.affiliation: Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Dequan
authors.initials: D
authors.lastname: Li
authors.forename: Fengya
authors.initials: F
authors.lastname: Nie
authors.forename: Lihui
authors.initials: L
authors.lastname: Wei
authors.forename: Benqiang
authors.initials: B
authors.lastname: Wei
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Chen
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D002414:Cations, Monovalent; D009154:Mutation; D009584:Nitrogen; D010572:Pest Control, Biological; D012232:Rhizoctonia
chemical_list: D002414:Cations, Monovalent; D009584:Nitrogen