Genotypic variability in membrane thermo-stability in groundnut

High temperature is one of the major constraints, which destabilizes the yield of groundnut (Arachis hypogaea L.) in semi-arid tropics. Membrane thermostability is one of the important parameters to evaluate the genetic variability for heat stress. In our study, genotypic variations for membrane thermostability were examined by using the heat killing temperature and heat killing time as the selection index. The temperature needed to cause the 50% electrolyte leakage from heat stressed leaf tissue for 1 hour duration is taken as heat killing temperature. Similarly the time needed to cause the 50% electrolyte leakage from heat-stressed leaf tissue at 54.0°C is taken as heat killing time. Our results recorded the existence of genotypic variability among the genotypes for both heat killing temperature and heat killing time. A strong relationship between heat killing time and heat killing temperature suggested that any of the two parameters can be used as screening tool for heat tolerance in groundnut. Comparatively, wider range of the heat killing time (43 to 68 min.) than that of heat killing temperature (53.4 to 55.2 °C) suggested that heat killing time would be more useful selection criteria for heat tolerance in groundnut. Moreover, the varieties which are able to tolerate moderately higher temperature for longer durations are very important in breeding for heat tolerance rather than the varieties which can withstand very high temperature but for less duration.