PHYSIOLOGICAL EVALUATION OF WHEAT GENOTYPES FOR HEAT STRESS TOLERANCE

Abstract

To evaluate wheat genotypes under high temperature stress during germination and early seedling growth, ten wheat genotypes were tested in 25 and 35ºC temperature at Crop Physiology and Ecology Laboratory, Hajee Mohammad Danesh Science and Technology University, Dinajpur during September 2015 to October 2015. Speed of germination as expressed by rate of germination and germination vigor index of all wheat genotypes was increased due to high temperature (35ºC) during germination of seeds. Shoot length, root length, seedling dry weight and seed reserve utilization efficiency were found to be affected due to high germination temperature. But the magnitude of reduction of these parameters due to high germination temperature was not similar for all wheat genotypes. Among the ten wheat genotypes BARI Gom 29 and BARI Gom 26 showing higher pooled stress tolerance index (STI) and E 22 and BARI Gom 27 showing lower STI were selected as comparatively high temperature tolerant and sensitive genotypes for the next experiment. These four wheat genotypes were grown under normal and post anthesis heat stress condition sowing them on 30 November and 30 December at the research field of Crop Physiology and Ecology department, Hajee Mohammad Danesh Science and Technology University, Dinajpur during the period of November 2015 to April 2016 to evaluate the sensitivity of physiological traits of wheat resulting reduced grain yield under heat stress condition. The experiment was laid out in a Split plot design with three replications. BARI Gom 29 and BARI Gom 26 which were comparative tolerant based on germination characters showed greater cell membrane thermostability, greater stability of flag leaf chlorophyll, higher level of proline in flag leaf and kernel, lower level of soluble sugar in flag leaf and kernel and greater ability to keep the canopy cooler compared to BARI Gom 27 and E 22 under heat stress condition. Better yield components such as ears m-2 , grains spike-1 and grain size under heat stress condition contributed to better tolerance of BARI Gom 29 and BARI Gom 26. The order of tolerance based on grain yield was BARI Gom 26 > BARI Gom 29 > E 22 > BARI Gom 27.