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journal1 ›› 2017, Vol. 33 ›› Issue (4): 537-544.DOI: 10.16409/j.cnki.2095-039x.2017.04.015

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Selection of Insecticidal and Fungicidal Engineering Strain by Protoplasts Fusion of Inactivated Parental Strain Bacillus thuringiensis and Bacillus subtilis

ZHAO Xiaoyan, ZHOU Fangyuan, ZHOU Hongzi, WU Xiaoqing, ZHANG Guangzhi, ZHANG Xinjian, LI Tianyuan, XIE Xueying   

  1. Shandong Provincial Key Laboratory of Applied Microbiology/Institute of Ecology, Shandong Academy of Sciences, Jinan 250014, China
  • Received:2016-10-13 Online:2017-08-08 Published:2017-08-11

Abstract: Fermentation broth of Bacillus thuringiensis B7 caused 85.06% mortality of Plutella xylostella 2nd instar larvae at 96 h after treatment. Bacillus subtilis TL2 showed antagonistic effects on pathogenic fungi Fusarium oxysporum and FPhytophthora capsici, which reduced more than 60% of mycelial growth of these fungi at 5 d after confronting incubation. The best condition for protoplast obtaining, complete inactivation, and protoplast fusion of these two bacterial strains were determined. The best protoplast formation rate and regeneration rate were 85.00% and 29.41%, respectively, for strain B7 under 1.0 mg/L of lysozyme for 70 min. The best protoplast formation rate and regeneration rate were 80.00% and 25.00%, respectively, for strain TL2 under 1.25 mg/L of lysozyme for 50 min. The best protoplasts inactivation condition for strain TL2 was water bath at 60℃ for 35 min, and for strain B7, ultraviolet radiation for 25min. The best protoplast fusion condition was water bath at 30℃ for 20 min. Then the mixture was spread on regeneration medium plates. Seventeen fusants were obtained after 10 times of subcultures, and the fusant TLB15 showed both high insecticidal and fungicidal activity. Fermentation broth of TLB15 resulted in 93.44% mortality of P. xylostella 2nd instar larvae at 96 h after treatment and inhibited 60.00% and 62.79% of mycelial growth of F. oxysporum and P. capsici, respectively (5 d of confrontation cultivation).

Key words: protoplast fusion, Bacillus subtilis, Bacillus thuringiensis

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