小菜蛾高致病力绿僵菌的筛选、鉴定及培养特性研究

为开发蔬菜害虫小菜蛾Plutella xylostella的高致病力真菌生物农药,以3龄小菜蛾幼虫为供试虫源,测定了25株虫生真菌菌株对小菜蛾的致病力,从中筛选出1株对小菜蛾幼虫有较高致病力的菌株CQM125。生测结果显示,在20℃、1.0×108孢子mL 1菌株CQM125菌液处理小菜蛾幼虫的LT50为3.97 d;25℃、5.0×107孢子mL 1菌液的LT50为2.44 d;在25℃下,第7 d的LC50为2.31×104孢子mL 1;接种处理后,20℃、8 d的小菜蛾死亡率为84.22%,对小菜蛾表现出良好的控制效果。依据菌株的形态特征、培养性状和rDNA ITS序列分析将菌株CQM125鉴定为金龟子绿僵菌Metarhizium anisopliae。对该菌株的培养基和培养条件进行了优化,优化后的产孢培养基为PPDA,其中葡萄糖2%,蛋白胨0.5%;最适产孢温度30℃,最适产孢pH值为6.0;最适光照条件为前6 d黑暗,后8 d光照。

Screening, Identification and Culture Characteristics of a Highly Pathogenic Strain of Metarhizium against Plutella xylostella

To develop high pathogenic fungal biopesticide against diamondback moth,a serious pest in vegetable fields,virulence of 25 fungal strains against the 3rd larvae of Plutella xylostella were evaluated in laboratory.One high virulent isolate,CQM125,was obtained.Bioassay results showed that for the 3rdinstar larvae,the LT50values were 3.97 d（1.0×108spores mL 1,20 ℃） and 2.44 d（5.0×107spores mL 1,25 ℃）,respectively.The LC50value（7 d,25 ℃） was 2.31×104 spores mL 1,and the cumulative mortality（8 d,20 ℃） reached 84.22%.Based on morphology feature,culture characteristics and rDNA ITS sequence,the strain CQM125 was identified to be Metarhizium anisopliae.Optimization of cultural conditions showed that PPDA is the best medium for hyphal growth and sporulation,which contains 2% glucose and 0.5% peptone;the optimal temperature and pH value were 30 ℃ and 6.0,respectively.The 6 d dark followed by 8 d light was the suitable photoperiod for the sporulation.