球孢白僵菌生物学特性与其对不同昆虫侵染差异相关性分析

Correlation between Biological Characteristics of Beauveria bassiana and Its Cuticle Infection on Different Insects

球孢白僵菌对不同目标昆虫的侵染能力存在很大差异。应用4株不同寄主来源的球孢白僵菌对2龄小菜蛾和棉铃虫幼虫进行毒力测定,扫描电镜观察分生孢子在试虫体表的萌发及侵染过程,同时测定了4菌株的生长速率、产孢量和孢外酶水平等生物学特性。结果表明,供试菌株中HFW-05的生长速率及酶活性均高于其余3菌株;菌株HFW-05对小菜蛾致病力较高,处理6 d后校正死亡率为87.1%,其余3株为30%左右;4菌株对棉铃虫6 d后校正死亡率均低于20%。扫描电镜观察结果表明,菌株HFW-05附着在小菜蛾表皮12 h后,孢子萌发后直接或产生较短芽管穿透表皮,36 h后,未穿透小菜蛾表皮的菌丝体断裂为芽生孢子;其余处理分生孢子在试虫表皮均能萌发,但芽管多呈蔓延生长直至断裂为芽生孢子,未能有效穿透寄主表皮,且孢子生长周期均长于菌株HFW-05。单纯依据孢子萌发率、产孢量或酶活评价筛选高毒力菌株是不够的。

There were significant differences of infection ability of Beauveria bassiana on different target insect. Toxicity test was carried out using four different origin strains orB. bassiana against 2nd instar larvae of diamond back moth Plutella xylostella and cotton bollworm Helicoverpa armigera. Conidia germination and infection on the larval body surface of four strains were observed by scanning electron microscopic. We determined the growth rate, sporulation and extracellular enzyme activity of these strains. The results showed that the growth rate and enzyme activity of strain HFW-05 were higher than those of the other three strains. The corrected mortality of strain HFW-05 to diamond back moth was 87.1% at 6 d after inoculation. While the other three strains were about 30% to diamond back moth. The corrected mortality of four strains was lower than 20% for cotton bollworm after 6 d infection. The scanning electron microscopic observation results showed that strain HFW-05 directly penetrated diamondback moth epidermal after germinated or produced a shorter germ tube after 12 h infection. Mycelium failed to penetrate host cuticle but grew to break as blastospores after 36 h infection. For other treatments, scanning electron microscope results showed that conidia failed to penetrate host cuticle by cuticle infection, but affixed to the growth on the cuticle surface of host, and grew to break as blastospores with longer growth cycle than conidia of strain HFW-05. The results indicated it was not enough to evaluate and screen high virulent strains purely based on germination rate, conidia production or enzyme activity.