两株绿僵菌菌株的分离鉴定及其对花生蛴螬的致病力

Identification of Two Metarhizium Species and Bioassay of Their Virulence against the White Grubs of Peanut

从山东日照、青岛两地的花生生产示范大田采集得到天然罹病的花生蛴螬僵虫中,分离得到两株绿僵菌菌株(Metarhizium spp.)。对两株菌株的ITS1-5.8S rRNA-ITS2区域进行序列分析,并结合菌株的形态和培养特征,分别确定为平沙绿僵菌M.pingshaense(CQM132)和贵州绿僵菌M.guizhouense(CQM135)。筛选了菌株CQM132和CQM135的最适培养温度和最适培养基,结果表明两个菌株均在28℃温度条件下,在PPDA培养基上的生长速度最快且产孢时间显著最短。室内测定了菌株CQM132和CQM135对铜绿丽金龟和暗黑腮金龟幼虫(蛴螬)的致病力。结果表明,菌株CQM132和CQM135对铜绿丽金龟和暗黑腮金龟幼虫均具有较强的毒力。菌株CQM132的高浓度孢悬液(1.1×107～1.1×108孢子mL-1)对两种金龟幼虫的累计死亡率均达到85%以上,致死中时LT50≤7.58 d。菌株CQM135的高浓度孢悬液(1.1×107～1.1×108孢子mL-1)对两种蛴螬的累计死亡率均达到90%以上,致死中时LT50≤6.85 d。相比而言,菌株CQM135对两种蛴螬的致病力略优于菌株CQM132,可以作为优良菌株进一步研究。

In this study, two species of Metarhizium spp. were isolated from natural cadaver of white grubs from peanut planting field in Rizhao and Qingdao, Shandong province. The two Metarhizium species were identified as M. pingshaense for strain CQM132 and M. guizhouense for strain CQM135 based on the sequence of their ITS1-5.8SrRNA-ITS2 and morphological and cultural characteristics. The optimum culture temperature and medium for strain CQM132 and CQM135 were screened, results showed that the optimal culture temperature for the two strains was 28℃ and PPDA was the best media for hyphal growing and sporulation of the two strains. Virulence of CQM132 and CQM 135 to the larvae （white grubs） of Anomala corpulenta and Holotrichia parallela was evaluated in the laboratory. Bioassay results indicated that the two strains were highly virulent against two species of white grubs. The corrected accumulative mortality on the two grubs was over 85% with the suspension at a high concentration （1.1×107--1.1×108 spore-mL-1） of CQM132, and the LTs0was less than 7.58 d; while the corrected accumulative mortality against two grubs was over 90% with the spore suspension at a concentration 1.1× 107-1.1× 108 spore-mL-1 of CQM135, and LTs0 was less than 6.85 d. The results indicated that the virulence of CQM135 was more aggressive than CQM132 and it could be used as a potential biocontrol agent against white grubs in the peanut field.