河北异小杆线虫一品系的分类鉴定及其对蛴螬致病力的测定

昆虫病原线虫是一种有应用潜力的地下害虫生物防治因子。本研究利用形态学特征和ITS-rDNA分析方法对从河北省沧州分离的异小杆线虫一品系进行了鉴定, 并在室内测定比较了其对蛴螬的致病力。通过对该线虫侵染期幼虫和雄性成虫主要形态学特征的参数测量, 发现其与嗜菌异小杆线虫Heterorhabditis bacteriophora的形态特征最为相近；同时ITS1-rDNA序列比对和系统发育学分析结果显示其与嗜菌异小杆线虫亲缘关系最近。结合形态学和分子生物学特征, 确定该线虫为嗜菌异小杆线虫沧州品系。该线虫对蛴螬（华北大黑鳃金龟Holotrichia oblita、暗黑鳃金龟H. parallela和铜绿丽金龟Anomala corpulenta 3种金龟子的2龄幼虫）的致病力研究结果表明：处理72 h后, 暗黑鳃金龟幼虫死亡率显著高于另外两种金龟子幼虫 (P<0.05)；处理120 h后, 暗黑鳃金龟和铜绿丽金龟幼虫的死亡率分别达到93.3%和80.0%, 二者无显著差异 (P>0.05), 可见该线虫对它们有较强的致病力。不同线虫对暗黑鳃金龟幼虫的致病力结果显示, 嗜菌异小杆线虫沧州品系侵染96 h后, 幼虫的死亡率显著高于Steinernema feltiae和S. longicaudum两种线虫的处理 (P<0.05) , 说明嗜菌异小杆线虫沧州品系的致病力显著高于另外两种线虫。

Identification of a strain of Heterorhabditis (Nematoda: Heterorhabditidae) from Hebei and its virulence to white grubs

Entomopathogenic nematode is a potential factor for biological control of underground pest. A strain of Heterorhabditis isolated from Cangzhou of Hebei province was identified based on the morphological characters and ITS-rDNA sequence analysis, its virulence to white grubs was also determined in the laboratory. Morphological measurement of infective juveniles and males showed that the population was most closely related to Heterorhabditis bacteriophora, while the results of ITS1-rDNA sequences alignment and phylogenetic analysis indicated that the population had the closest genetic relationship with H. bacteriophora. Based on the morphology and biological characters, the population was identified as H. bacteriophora strain Cangzhou. Pathogenicity tests of the nematode to white grubs (2nd instar larvae of Holotrichia oblita, H. parallela and Anomala corpulenta) showed that the mortality of H. Parallela. Larvae was significantly higher than that of the other two scarabes ( P < 0.05 ) after infection of 72 h. After 120 h, the mortality of H. Parallela and A. Corpulenta larvae were 93. 3% and 80.0% , respectively, without significant difference ( P > 0. 05 ), suggesting that the nematode has strong virulence against them. Virulence tests of different nematodes to larvae of H. parallela indicated that the larvae which were infected by H. Bacteriophora strain Cangzhou had higher mortality than those infected by Steinernema feltiae and S. longicaudum after infection of 96 h (P <0. 05) , suggesting that the virulence of H. Bacteriophora strain Cangzhou is significantly higher than the other two nematodes.