Evaluation of Screening Techniques for Heat Tolerance in Wheat

Cell membrane thermal stability, antioxidant activity, phenolics content, Paraquat tolerance and kernel weight were compared for their ability to identify heat tolerant genotypes. Four wheat (Triticum aestivum L.) genotypes, Kauz, MTRWA116, Opata and W7984 were used in this study, Kauz and MTRWA116 being thermotolerant and thermosensitive, respectively. Plants were exposed to high temperatures of 39 and 35 degrees C and then their measurements form different techniques were compared to each other and to the controls. The experiments were run several times to measure the repeatability of the measurements. Although the amount of phenolic compounds increased under stress condition, there was no significant difference between tolerant and susceptible varieties. Membrane thermal stability, antioxidant activity, phenolics content and Paraquat tolerance did not provide repeatable data. Nor did they discriminate among tolerant and susceptible genotypes. Kernel weight, however, varied between tolerant and susceptible genotypes. The results indicate that kernel weight is more suited for heat stress screening than other physioloical techniques evaluated in this study.