生防真菌分生孢子抗氧化能力与多糖含量的关系

作为重要的丝孢类昆虫病原真菌,球孢白僵菌和玫烟色棒束孢因其易于生产和环境友好等优点而在害虫生防防治中受到广泛青睐。为初步探求孢子耐氧化力及其与孢子多糖含量的关系,球孢白僵菌和玫烟色棒束孢11株菌经胁迫后的残存指数随氧化剂H2O2浓度增加而减小。所有菌株的残存指数均能良好地与Logistic方程拟合,并计算出各菌株在氧化胁迫条件下的半致死浓度。结果显示玫烟色棒束孢孢子的耐氧化力强于球孢白僵菌。两种真菌的分生孢子耐氧力与各自多糖含量呈现良好线性正相关。培养基碳源成分和浓度变化可影响球孢白僵菌孢子耐氧化力,但耐氧化力与多糖含量依旧呈现线性正相关。由此可见,生防真菌分生孢子的耐氧化力的确与多糖积累有关,并在一定程度上受培养条件的调节。研究结果有望为提高生防真菌孢子环境稳定性提供新的策略。

Relationships between oxidative tolerance and polysaccharide content in aerial conidia of the entomopathogenic fungi

Entomopathogenic hyphomycete has long been widely applied in biocontrol of insect pests due to easy production, formulation and environmental safety. This study was to illustrate the relationship between the oxidative tolerance and the polysaccharide content in aerial conidia of Beauveria bassiana and Isaria fumosorosa. Survival indices of 11 isolates were separately assessed as a ratio of the viability of conidia exposed to 10min stress with H2O2 over that of unstressed conidia and fitted well to a survival model (r2>0.95). For a given isolate, the fitted model generated an LD50, the concentration for 50% viability loss under the stress. As a result, I. fumosorosea was more tolerant to oxidative stress than B. bassiana. The LD50 for B. bassiana and I. fumosorosea was correlated well to the conidial polysaccharide content of the respective strain. The conidial contents of B. bassiana could be modified by changing the concentration and type of sugar in media. However, the survival indices of isolate were still correlated well to the polysaccharide content from conidia produced on glucose-, sucrose-, or starch-based media. The relationship between conidial polysaccharide content and oxidative tolerance suggested a new way to search for fungal biocontrol agents with more environmental stability.