亚洲白僵菌的分离鉴定及其对铜绿丽金龟幼虫的致病力

Isolation and identification of the insect pathogenic fungus Beauveria asiatica and its pathogenicity tocopper-green chafer Anomala corpulenta larvae

为挖掘对铜绿丽金龟Anomala corpulenta幼虫有高致病力的生防真菌,采用组织分离法对采集自花生田自然罹病铜绿丽金龟上的寄生真菌进行分离培养,观察分离菌株的生长性状并结合rDNA的ITS和EF1-a序列系统发育分析对其进行鉴定,比较该菌株与其他已知菌株的生物学特性差异和对铜绿丽金龟2龄幼虫的致病力,并基于侵染浓度、温度和相对湿度来明确其适宜施用条件。结果表明:从自然罹病铜绿丽金龟上分离获得1株菌株,结合形态学特征和分子生物学分析结果最终将该菌株鉴定为亚洲白僵菌Beauveria asiatica,命名为BaT;BaT菌株在恒温光照培养条件下,在萨氏培养基上的菌丝生长速率为3.49 mm/d,显著低于金龟子绿僵菌Metarhizium anisopliae菌株Ma26的菌丝生长速率(5.15 mm/d),但显著高于球孢白僵菌B.bassiana菌株Bb58、Bb31和Bb48的菌丝生长速率(3.11~3.34 mm/d);BaT菌株在培养15 d时产孢量为6.02×10^(7)个/cm^(2),明显低于球孢白僵菌菌株Bb58、Bb31和Bb48的产孢量(7.88×10^(7)~9.74×10^(7)个/cm^(2)),但显著高于金龟子绿僵菌菌株Ma26的产孢量;该菌株12 h孢子萌发率为96.22%,与其他4株菌株的孢子萌发率无显著差异。在相同侵染浓度下,铜绿丽金龟2龄幼虫接种菌株BaT后的校正死亡率随着时间的延长而升高,接种后15 d开始显著高于接种其余4株菌株幼虫的校正死亡率。菌株BaT对铜绿丽金龟2龄幼虫的致病力随着侵染浓度的增加而显著增加,在最高浓度1×10~8个/g处理后19 d时校正死亡率达到79.42%;对铜绿丽金龟2龄幼虫的致死中浓度LC50为2.01×10^(7)个/g。菌株BaT侵染铜绿丽金龟幼虫的适宜温度为20~30℃,25℃为最适宜温度;适宜相对湿度为[80%~90%)。表明亚洲白僵菌菌株BaT对铜绿丽金龟幼虫有较好的防控效果,可用于该虫的生物防治。

To identify highly pathogenic strains against copper-green chafer Anomala corpulenta larvae,entomopathogenic fungi were isolated and cultured from naturally infected A.corpulenta in the peanut field.Strain identification was based on morphological characteristics and phylogenetic analysis of the ITS and EF1-αregions of rDNA.The biological characteristics and pathogenicity of the isolated strain were compared with known strains.The strain’s efficacy was tested under various spore concentrations,temperatures,and humidity levels to determine the optimal conditions for larval control.The results identified a strain named BaT as Beauveria asiatica based on morphological and molecular analysis.The daily growth rate of BaT was 3.49 mm/d under constant temperature and illumination,which was significantly lower than that of Metarhizium anisopliae Ma26(5.15 mm/d)but significantl higher than that of B.assiana Bb58,Bb31,and Bb48(3.11-3.34 mm/d).On the 15th day,the spore production rate of BaT was 6.02×10^(7)spores/cm^(2),lower than strains Bb58,Bb31,and Bb48 but significantl higher than Ma26.The spore germination rate of BaT reached 96.22%within 12 hours,with no significant difference compared to the other four strains.Under the same infection conditions,the mortality rate of BaTinfected larvae increased over time and was significantly higher than that of the other four strains on the 15th day.At a concentration of 1×108 spores/g over 19 days,BaT achieved a corrected mortality rate of 79.42%,significantly higher than other concentrations tested.The LC50 of BaT for 2nd instar larvae of A.corpulenta was 2.01×10^(7)spores/g.The optimum temperature range for BaT infection was 20-30℃,with 25℃being the most effective.The optimal humidity was[80%-90%).These results indicate that BaT could be an effective agent for the biocontrol of A.corpulenta larvae.