Abstract
Bean (Phaseolus vulgaris L.) cultivars for the Caribbean need greater heat tolerance. The principal objective of this research was to study the inheritance of heat tolerance in an Andean population. Field experiments were conducted over a two-year period (1999-2000) to test the performance of 81 bean lines derived from the cross 'DOR 303/Indeterminate Jamaica Red'. During the summer months, PR9919-116 and PR9919-168 produced significantly greater seed yields than the heat tolerant parent 'Indeterminate Jamaica Red'. Near narrow sense heritability estimates for seed yield per plant, number of pods per plant and number of seed per pod were low to intermediate, ranging from 0.16 to 0.62, thus suggesting that screening for tolerance to higher temperatures should be conducted by using advanced generation lines in replicated trials. Additive genetic correlations between seed yield per plant and number of pods per plant, number of seed per pod, and hundred seed weight were positive and significant. There were also positive and significant additive genetic correlations between hundred seed weight and number of pods per plant. Given the large additive genetic correlations between hundred seed weight and seed yield per plant and the high narrow sense heritabilities for hundred seed weight, indirect selection for larger seed size could have been used to select for heat tolerance. The line PR9920-13 had the highest mean seed yield in the winter plantings and the third greatest mean seed yield in the summer plantings. However, the performance of the other lines in the trials suggests that selection for seed yield in the winter months would not guarantee the identification of highyielding lines for the summer months. Selection for adaptation to high temperature environments requires the evaluation of bean lines during the summer months. Mean percentage pollen viability of the lines most tolerant to heat was significantly greater than pollen viability of the heat sensitive lines. Only one breeding line, PR9920-171, combined the heat tolerance of indeterminate Jamaica Red and the resistance to bean golden yellow mosaic virus of DOR 303.