球孢白僵菌野生及转基因菌株的退化

球孢白僵菌在人工培养基上继代培养容易发生退化变异,表现为菌丝徒长以及产孢量减少和毒力的逐渐下降,给真菌杀虫剂的生产和使用造成较大的损失.没有丢失被插入的外源毒力基因的工程株同样出现退化.培养基成分和含水量以及培养温度和光照等环境因子皆可不同程度地诱发退化的发生,但退化主要由其遗传机制决定,包括线粒体基因突变、异核现象、准性生殖、核基因突变以及有性重组等；菌落局变实质上也是菌种老化的征兆.真菌杀虫剂生产中防止退化的对策除减少传代次数外,还要根据具体菌株确定适宜的环境控制细则.

Degeneration of wild type and transgenic strains of Beauveria bassiana

Successive subculture of Beauveria bassiana is subject to degenerative variation, with phenotypic nourishing hyphal growth and gradual decline of sporulation and virulence on hosts, resulting in dramatic loss of production and application of fungal insecticides. Degeneration also happens to transgenic strain with inserted virulent gene not lost. Components and water content of medium, and environmental factors such as incubation temperature and illumination variously induce saltation, but degeneration is mainly controlled by genetic mechanisms, including mutation of mitochondrial genome, heterokaryosis, parasexuality, mutation of nuclear genome as well as sexual recombination; saltation is essentially a sign of ageing. As a strategy of degeneration control for fungal insecticide production, environment control details should be carried out based on specific isolate, in addition to decrease of subculturing.