Selection for high temperature tolerance in some native Steinernema and Heterorhabditis species

Effect of heat-shock treatment on survival and viability of some isolates of Steinernema sps. and Heterorhabditis spp. at relatively higher temperatures was studied. Survival, infectivity and multiplication were unaffected at sub-lethal temperatures 35 and 37°C. Exposure to 40°C affected the survival and infectivity of both Steinernema spp. and Heterorhabditis spp. Pre-conditioning at 37°C enhanced survival rate and viability of IJs on subsequent exposure at 40°C. Studies on F1 generation revealed the superior tolerance of Fl generation to high temperature compared to wild population. Pathogenicity of F1 generation was only marginally affected after exposure to 42°C for 3 and 4 h whereas wild population experienced marked reduction in pathogenicity under the same conditions. This is the first successful attempt at detecting thermotolerance in native isolates in India.