Application of stress indices for heat tolerance screening of common bean

Common bean is adapted to relatively cool climatic conditions and temperatures of > 30 degrees C during the day or > 20 degrees C at night result in yield reduction. The long-term goal of breeding for heat tolerance is the development of germplasm with improved field level tolerance under variable temperature conditions. Using previously developed stress indices, this study presents results from high temperature screening of 14 genotypes in both the greenhouse and field in Puerto Rico. A total of three sets of paired trials were conducted in the field and in the greenhouse under high temperature (stress) and lower temperature (low-stress) conditions. The geometric mean (GM), stress tolerance index (STI) and stress susceptibility index (SSI) were used to evaluate the genotypic performance under stress and low-stress conditions. The results indicate that it was possible to identify superior genotypes for heat tolerance based on their stress indices. In this evaluation of heat tolerance indices, STI and GM, although correlated, were found to be effective stress indices for the selection of genotypes with good yield potential under stress and low-stress conditions.