Selection and Inheritance of Heat Tolerance in the Common Bean by Use of Conductivity

Abstract

Abstract Inheritance and selection of heat tolerance were investigated in common bean (Phaseolus vulgaris L.). Parental, F1, backcross, and F2 populations from the crosses PI 271998 × BBL 47, PI 271998 × 80 BP-6 and 5BP-7 × BBL 47 were used in the inheritance study. Parental, F2, F3 and backcross populations of the cross PI 271998 × BBL 47 were used to estimate selection gain. Plants were evaluated for heat tolerance by the conductivity method after 32 days in the growth chamber at 20°/15°C (day/night) and acclimation at 37° for 24 hr. The joint scaling test indicated that the additive-dominance model was adequate to explain heat tolerance in crosses PI 271998 × BBL 47 and 5BP-7 × BBL 47. The major variation for tolerance for these 2 crosses may be controlled by a small number of genes. The additive-dominance model was inadequate for PI 271998 × 80BP-6, however, and epistasis was present. Narrow sense heritability estimates ranged from 2.9% to 24.0%, indicating relatively small additive effects. Broad sense heritability estimates ranged from 0.0% to 21.6%, suggesting sizable environmental effects. Realized heritability from selection for tolerant F2 plants was 7.9%. These estimates perhaps represent the lower limit of heritability for heat tolerance. The conductivity method could be considered for evaluating heat tolerance in a breeding program but should be more effective in screening F3 families than individual F2 plants.