Differential response of common bean genotypes to high temperature

Yield components of 24 common bean (Phaseolus vulgaris L.) genotypes were evaluated following exposure during reproductive development to four greenhouse day/night temperature treatments (24 degreesC/21 degreesC, 27 degreesC/24 degreesC, 30 degreesC/27 degreesC and 33 degreesC/30 degreesC). Genotypes included 12 snap beans, two wax beans, six dry beans, and four common bean accessions; 18 genotypes were previously described as heat-tolerant and three were heat-sensitive controls. The highest temperature treatment reduced seed number, pod number, mean seed weight and seeds/pod an average of 83%, 63%, 47%, and 73%, respectively. A heat susceptibility index (S) measuring yield stability underhigh temperatures indicated that 'Brio', 'Carson', 'G122', 'HB 1880', 'HT 20', 'HT 38', 'Opus', and 'Venture' were heat tolerant. Heat-tolerant genotypes displayed differential responses to high temperature, suggesting different genetic control of heat tolerance mechanisms. Genotypes with moderate heat tolerance, including 'Barrier' and 'Hystyle', showed stable yields in the 30 degreesC/27 degreesC treatment only, indicating this regime is optimal for screening common bean materials of unknown heat tolerance. 'Haibushi', 'Indeterminate Jamaica Red', and 'Tio Canela-75' were previously described as heat tolerant but exhibited a heat-sensitive reaction in this study. Heat-sensitive genotypes 'Haibushi' and 'Labrador' maintained mean seed weight under high temperature. This data will help utilize nonallelic heat tolerance genes in development of bean varieties grown in high temperature environments.