3种绿僵菌对筛胸梳爪叩甲幼虫的毒力及保护酶活性的影响

Effects of Three Different Metarhizium Strains on Virulence and Protective Enzymes Activities of Melanotus cribricollis larvae

【目的】探索绿僵菌侵染后竹林筛胸梳爪叩甲幼虫保护酶系统的应答反应,为筛选高致病力的绿僵菌菌株提供依据。【方法】生物测定平沙绿僵菌WP08菌株、金龟子绿僵菌WTKH菌株及蝗虫绿僵菌菌株3种菌株在不同浓度条件下对该幼虫的致病力,同时测定不同侵染时期幼虫超氧化物歧化酶(SOD)、过氧化物酶(POD)及过氧化氢酶(CAT)3种保护酶含量及活性变化情况。【结果】3株绿僵菌对筛胸梳爪叩甲幼虫均具有致死性,WP08菌株最优,WTKH菌株次之,蝗虫绿僵菌最低。不同菌株的致病力随着浓度的增加而提高,WP08菌株在108spore·g^(-1)干土浓度条件下的致病效果最好,16天时供试幼虫已经全部死亡,但与107spore·g^(-1)干土浓度条件下的致病效果无显著差异。幼虫的3种保护酶在抗绿僵菌侵染过程中其活性变化趋势不同,SOD活性变化无显著差异,CAT活性变化则表现为先下降后上升再下降的趋势,POD活性波动虽与CAT相似,但其后期(5~7天)差异不显著。【结论】平沙绿僵菌WP08菌株对筛胸梳爪叩甲幼虫的致病性优于其他2种菌株,可作为林间应用的首选菌株。绿僵菌可对竹林金针虫体内的3种保护酶活性产生不同程度的影响,且在本次取样时间内CAT的活性变化较明显。

【Objective】The bamboo wireworm（ Melanotus cribricollis larvae） is one of the most rampant forest pests causing serious damage to bamboo shoots in southern China. It is hard to monitor and control this pest till now. Metarhizium spp. can be used for biocontrol of the wireworm. The purpose of this study is to screen high pathogenicity Metarhizium strain and explore the immune response of protective enzyme system in the wireworm after the fungal infection. 【Method 】The pathogenicity tests by applying three Metarhizium strains against the pest larvae with different spore concentrations were conducted. The dynamic activity changes of three protective enzymes in the host larvae,i. e. superoxide dismutase（ SOD）,peroxidase（ POD）,and catalase（ CAT）,were also determined during different infect periods.【Result】Results showed that all the three isolates possessed lethal property were able to infest M. cirbricollis larvae,among which M. pingshaense WP08 strain was the best,M. anisopliae WTKH strain was the second and M. acridum strain the last. The pathogenicity was enhanced with the increased spore concentration. With 108 spore·g^-1 DW soil,M. pingshaense WP08 strain exhibited the highest toxicity and all of the tested larvae died in 16 d,but M. pingshaense WP08 strain with 107 spore·g^-1 DW soil had no significant pathogenicity. There was difference in the dynamic change trends of three protective enzyme activities. There was no significant difference in the SOD activity. However,the CAT activity firstly down-regulated,then up-regulated and declined again subsequently,and the POD activity showed similar fluctuation trend to the CAT activity,but there was no significant difference at the late stage（ 5-7 d）. 【Conclusion】The present study indicated that M. pingshaense WP08 strain was the best entomopathogenic fungus to infect M. cribricollis larvae compared with other two strains. Therefore,the strain could be first selected as a biocontrol agent for control of the wireworm in bamboo forests. The fungal infection influenced activities of the three protective enzymes,especially to CAT activity.