玫烟色棒束孢的生物学特性与其对小菜蛾致病力的相关性

Correlation between biological characteristics of Isaria fumosorosea and its pathogenicity against Plutella xylostella

测定了玫烟色棒束孢原始亲本菌株PFCF—O、退化亲本菌株PFCF—D和单孢分离子菌株PF-CF．D58、PFCF．D20、PFCF．D50的菌落生长速率、产孢量、孢予萌发率和胞外蛋白酶水平等生物学指标以及各菌株对小菜蛾2龄幼虫的校正死亡率。结果表明，菌株PFCF—O的生长速率呈先快后慢的趋势，产孢量为2．7×10^7个／mL，孢子萌发率为62．59％，胞外蛋白酶水平为1．16，对小菜蛾2龄幼虫校正死亡率达97．74％。而菌株PFCF．D、PFCF—D20、PFCF—D50和PFCF—D58间平均生长速率和孢子萌发率无显著差异，产孢量变化范围为1．05×10^7～2．34×10^7个／mL，胞外蛋白酶水平变化范围为1．02—1．07，各生物学指标及其对小菜蛾2龄幼虫的校正死亡率（19．86％～51．44％）都显著低于菌株PFCF-O。相关性分析结果显示，玫烟色棒束孢对小菜蛾的致病力与菌株生长初期的生长速率、产孢量、孢子萌发率和胞外蛋白酶水平呈极显著的正相关关系，与菌株生长后期的生长速率呈极显著负相关关系。

In order to explicit the correlation between biological characteristic and pathogenicity of Isaria fumosorosea （ = Paecilornyces fumosoroseus ） to Plutella xylostella , five L fumosorosea strains, including original father strain PFCF-O, degenerated father strain PFCF-D, single-spore isolates PFCF-D58, PFCF- D20, and PFCF-D50, which isolated from PFCF-D, were assayed on sporulation, growth rate, spore germinate rate, extracellular protease and their pathogenicity to the 2nd instar larva of P. xylostella. The results showed that the growth rate of strain PFCF-O was fast at initial stage after inoculated to medial but slowed down with the time elapsed. The strain PFCF-O appeared an obviously higher sporulation （2.7 × 10^7 conidial/mL） after 20 days culture, spore germinate rate （62.59%）, extracellular protease level （1.16） and corrected mortality （97.74%） to the 2nd instar larva compared to other strains. However, among the strains PFCF-D, PFCF-D20, PFCF-D50 and PFCF-D58, there were no significant differences on the growth rate and sporulation germinate rate. Sporulation of these strains was 1.05× 10^7 - 2.34 × 10^7 conidial/mL and extracellular protease level was 1.02 - 1.07. The corrected mortality of these four strains to the 2nd instar larva was 19.86% -51.44% , significantly lower than that of strain PFCF-O. The pathogenicity of L fumosorosea against P. xylostella significantly correlated to the sporulation, spore germinate rate, extraeellular protease level and strains growth rate of the initial stage after inoculated to medial, but negatively to the growth rate of the later stage after inoculated to the medial.