CHOICE OF PARENTS TO OBTAIN COMMON BEAN (PHASEOLUS-VULGARIS) CULTIVARS TOLERANT TO LOW-TEMPERATURES AT THE ADULT STAGE

We investigated the genetic control of low temperature tolerance and t he interaction among the combining abilities for locations and generat ions in order to improve common bean plant tolerance to low temperatur es at the adult stage. In the fall/winter of 1995, a complete diallel involving the F-3 and F-4 generations obtained from direct and recipro cal crosses among II parents was assessed in two locations (Lavras and Lambari, Minas Gerais). Data for grain yield (kg/ha), anthracnose inc idence and flowering period (Lavras) were analyzed. The genetic varian ce and broad sense heritability for grain yield were estimated within the segregant populations. The diallel, analysis was carried out using method ill, described by Griffing (Aust. J. Biol. Sci. 9: 463-493,195 6). The parents differed in flowering period and grain yield under low temperature conditions at the adult phase. The line Small White was t he earliest; A-488, Ouro and ESAL 591 were the most cold tolerant, and CNF-05, Rio Vermelho and ESAL 501 were the most cold sensitive. Addit ive, dominance and reciprocal effects were observed, with the predomin ance of the additive. The reciprocal effect explained only a small par t of the variation, in a few populations. Only additive effects of the genes were observed for the flowering period. The general combining a bility (GCA) interactions indicated that the populations should be ass essed in several locations and generations in order to obtain reliable estimates. The A-488 x Ouro and Esal 591 x Ouro populations were the most promising for selection.