DESICCATION AND OXIDATIVE STRESS TOLERANCE AS MEASURES TO EVALUATE LONGEVITY IN ENTOMOPATHOGENIC NEMATODES

Abstract

Attempts at improving the performance of the entomopathogenicnematodes, Heterorhabditis bacteriophora for the bio-control of insect pests, are focused on the free-living forms, the infective juveniles (IJs).This stage is a non-feeding and developmentally arrested form in which the nematodes remain until environmental conditions become favourable. This study evaluated the IJ longevity of two Heterorhabditis bacteriophora inbred lines, H. bact IL-1 and H. bactIL-2, by subjecting the IJs to desiccation and oxidative stress conditions. Desiccation stress was induced on the IJs after exposing batches of the IJs to 7 concentrations of PEG 600. Tolerance to desiccation was expressed as water activity (aw), which is a measure of the relative proportion of unbound water available to the IJs for survival. Oxidative stress was induced on the IJs after exposing batches of the IJs to 60 mM of Hydrogen Peroxide (H2O2). The longevity of IJs from both inbred lines was compared to their tolerance to oxidative stress and desiccation. This study showed that tolerance to high oxidative stress correlates with tolerance to low water activity, which indicates the survival and extent of longevity inIJs of H. bacteriophora. This offers a firm support and validates the use of either oxidative stress or desiccation tolerance as a functionaltrait to correlate variations in environmental stress tolerance with the genes modulating longevity in H. bacteriophora IJs.