COMBINING ABILITY ANALYSIS OF PHYSIOLOGICAL TRAITS AND GRAIN YIELD IN MAIZE UNDER HEAT STRESS

Crop yield is reducing due to adverse effects of high temperature. Improvement of physiological status of maize plant against heat stress is important for a successful hybrid-breeding program. In the present study, six heat tolerant inbred lines, crossed in diallel mating design to develop F-1 progeny. Parental lines including 30F(1) crosses were sown in triplicate randomized complete block design to select better performing inbred lines and F-1 crosses for leaf temperature, cell membrane thermostability, stomatal conductance, transpiration rate and grain yield under normal and heat stress environments. Low GCA/SCA variance ratio (< 1) showed the predominance of over-dominant gene action for all traits under normal and high temperature conditions, except osmotic potential (dominant) under high temperature. Three inbred lines, NCIL-20-4, D-135 and NCIL-10-5, showed desirable significant GCA estimates for physiological traits and grain yield under normal and high temperature. Five F-1 crosses, D-103 x NCIL-10-5 (its reciprocal), D-103 x NCIL-30-5, NCIL-20-4 x NCIL-10-5 and NCIL10-5 x NCIL-30-5, proved as the best single crosses for physiological traits and grain yield under heat stress. Selected inbred lines and F-1 crosses will be a good source for development of heat resilient, high yielding maize hybrids in future hybrid-breeding programme.