Shapiro-Ilan David I, Brown Ian, Lewis Edwin E
USDA-ARS, Southeastern Fruit and Tree Nut Research Lab, Byron, GA 31008.
Department of Biology, Georgia Southwestern University, Americus, GA.
J Nematol. 2014 Mar;46(1):27-34.
The ability of entomopathogenic nematodes to tolerate environmental stress such as desiccating or freezing conditions, can contribute significantly to biocontrol efficacy. Thus, in selecting which nematode to use in a particular biocontrol program, it is important to be able to predict which strain or species to use in target areas where environmental stress is expected. Our objectives were to (i) compare inter- and intraspecific variation in freeze and desiccation tolerance among a broad array of entomopathogenic nematodes, and (ii) determine if freeze and desiccation tolerance are correlated. In laboratory studies we compared nematodes at two levels of relative humidity (RH) (97% and 85%) and exposure periods (24 and 48 h), and nematodes were exposed to freezing temperatures (-2°C) for 6 or 24 h. To assess interspecific variation, we compared ten species including seven that are of current or recent commercial interest: Heterorhabditis bacteriophora (VS), H. floridensis, H. georgiana, (Kesha), H. indica (HOM1), H. megidis (UK211), Steinernema carpocapsae (All), S. feltiae (SN), S. glaseri (VS), S. rarum (17C&E), and S. riobrave (355). To assess intraspecific variation we compared five strains of H. bacteriophora (Baine, Fl1-1, Hb, Oswego, and VS) and four strains of S. carpocapsae (All, Cxrd, DD136, and Sal), and S. riobrave (355, 38b, 7-12, and TP). S. carpocapsae exhibited the highest level of desiccation tolerance among species followed by S. feltiae and S. rarum; the heterorhabditid species exhibited the least desiccation tolerance and S. riobrave and S. glaseri were intermediate. No intraspecific variation was observed in desiccation tolerance; S. carpocapsae strains showed higher tolerance than all H. bacteriophora or S. riobrave strains yet there was no difference detected within species. In interspecies comparisons, poor freeze tolerance was observed in H. indica, and S. glaseri, S. rarum, and S. riobrave whereas H. georgiana and S. feltiae exhibited the highest freeze tolerance, particularly in the 24-h exposure period. Unlike desiccation tolerance, substantial intraspecies variation in freeze tolerance was observed among H. bacteriophora and S. riobrave strains, yet within species variation was not detected among S. carpocapsae strains. Correlation analysis did not detect a relationship between freezing and desiccation tolerance.
昆虫病原线虫耐受诸如干燥或冷冻条件等环境胁迫的能力，对生物防治效果有显著贡献。因此，在选择用于特定生物防治项目的线虫时，能够预测在预期存在环境胁迫的目标区域使用哪种菌株或物种非常重要。我们的目标是：（i）比较多种昆虫病原线虫在冷冻和干燥耐受性方面的种间和种内差异，以及（ii）确定冷冻耐受性和干燥耐受性是否相关。在实验室研究中，我们比较了处于两种相对湿度（RH）水平（97%和85%）和暴露时间段（24小时和48小时）的线虫，并且将线虫暴露于-2°C的冷冻温度下6小时或24小时。为了评估种间差异，我们比较了十个物种，包括七个目前或近期具有商业价值的物种：嗜菌异小杆线虫（VS）、佛罗里达异小杆线虫、佐治亚异小杆线虫（凯莎）、印度异小杆线虫（HOM1）、大异小杆线虫（UK211）、小卷蛾斯氏线虫（All）、夜蛾斯氏线虫（SN）、格氏斯氏线虫（VS）、稀少斯氏线虫（17C&E）和里奥布拉沃斯氏线虫（355）。为了评估种内差异，我们比较了嗜菌异小杆线虫的五个菌株（贝恩、Fl1-1、Hb、奥斯威戈和VS）、小卷蛾斯氏线虫的四个菌株（All、Cxrd、DD136和Sal）以及里奥布拉沃斯氏线虫的四个菌株（355、38b、7-12和TP）。小卷蛾斯氏线虫在物种中表现出最高水平的干燥耐受性，其次是夜蛾斯氏线虫和稀少斯氏线虫；异小杆线虫物种表现出最低的干燥耐受性，而里奥布拉沃斯氏线虫和格氏斯氏线虫处于中间水平。在干燥耐受性方面未观察到种内差异；小卷蛾斯氏线虫菌株比所有嗜菌异小杆线虫或里奥布拉沃斯氏线虫菌株表现出更高的耐受性，但在物种内未检测到差异。在种间比较中，印度异小杆线虫、格氏斯氏线虫、稀少斯氏线虫和里奥布拉沃斯氏线虫表现出较差的冷冻耐受性，而佐治亚异小杆线虫和夜蛾斯氏线虫表现出最高的冷冻耐受性，特别是在24小时暴露时间段。与干燥耐受性不同，在嗜菌异小杆线虫和里奥布拉沃斯氏线虫菌株中观察到冷冻耐受性存在显著的种内差异，但在小卷蛾斯氏线虫菌株中未检测到种内差异。相关性分析未检测到冷冻耐受性和干燥耐受性之间的关系。
