关键词:  球孢白僵菌, 松褐天牛, 航天诱变, 微生物防治, 优良菌株, 致病力

Abstract: 【Aim】 Monochamus alternatus is the major vector of pinewood nematode disease Bursaphelenchus xylopilus in China. We aimed to obtain high virulence mutants of Beauveria bassiana for biological control of M. alternatus through space mutation and laboratory selection. 【Methods】 A wild-type B. bassiana strain cfcc81357 isolated from M. alternatus had been carried into space for mutation induction by the Shenzhou 8 Spacecraft in 2011. Then, the obtained spore diluents were spread on PDA plate culture for single colony strains. Biological characteristics including the morphology, colony growing rate, spore production, conidia germination rate and conidial tolerance to thermal stress were compared between nine aerospace mutants and the original wild-type strain used as the control. Based on these results, three mutants (B159, B252 and B305) were adopted for further bioassay against the 4th instar larvae of M. alternatus. By sprinkling conidial powder on pine log surface and injecting conidia liquid into beetle-bored holes, the pathogenicity of the mutants B252 and B305 against M. alternatus larvae in pine logs was assessed. 【Results】 The results showed that these colony morphologies of nine aerospace mutants of B. bassiana changed at different degrees, of which six mutants had the colony growing rate obviously slowed down while only three mutants (B159, B252 and B305) produced conidial spores. Compared with the wild-type strain, mutant B252 and B305 had evidently higher virulence against M. alternatus, with a corrected mortality of 100% and the median lethal time (LT₅₀) of 8.08 and 8.56 d when applied at the concentration of 1.0×107 spores/mL, respectively. 【Conclusion】 The results suggest that aerospace mutants B252 and B305 may be excellent strains with great application potential for biological control of M. alternatus.

Key words:  Beauveria bassiana; Monochamus alternatus, aerospace mutagenesis, microbial control, superior strain, pathogenicity