Genotypic variation in response to high temperature at flowering in common bean (Phaseolus vulgaris L.)

Abstract

In controlled temperature glasshouses, 5 cultivars of Phaseolus vulgaris L. (cv. Actolac, and 4 Mexican cultivars: M 650, 659, 674, 685B) were subjected to super-optimal temperature (34/29�C day/night) stress pre-flowering (T2), pre- and post-flowering (T3), and post-flowering (T4). The stress treatments increased bud and flower production and dramatically increased abscission of buds, flowers, and pods compared with controls at 24-19�C. Actolac was the most sensitive to heat stress, while the Mexican cultivars displayed varying degrees of partial tolerance. For pod and seed production, M 674 was the most tolerant under T2, and M 685B the most tolerant under T4, with grain yields nearly equal to the control. This was achieved despite reduced seed weight, through increased seed set. Under T3 no cultivar produced seed. Cultivar M 659 was intermediate in stress reaction between Actolac and M 674 under T2, and M 650 was intermediate between Actolac and M 685B under T4. The data indicate that optimum growth temperatures for M 674 and M 685B may be greater than that for Actolac.