PATH ANALYSIS, CANONICAL CORRELATIONS AND GENETIC DIVERGENCE: I. AMONG PRIMARY AND SECONDARY CHARACTERS OF GRAIN YIELD IN BLACK BEANS (Phaseolus vulgaris L.) GENOTYPES

Abstract

Twenty tive black beans genotypes were evaluated in Lages, Santa Catarina, studying the influence of seven characters of agronomic importance on the grain production per unit arca. The experiment, in randomized blocks with thrce replications per treatment, was conducted in the growing season 1995/96 (November - January) . The objectives of this work were: I ) estimate the direct and indirect effects among the characters of agronomic importance, through path analysis; 2) estimate the association intcnsity between primary and secondary components of grain yield; 3) estimate the genetic divergence of twenty-five black bean genotypes, using Mahalanobis statistics. The first group of variables (primary components) was composed by the number of pods per plant, 1000 grains weight, and number of grains per pod; the second group (secondary components), by the number of days from emergency to flowering, number of days, from emergency to harvesting point, plant height and first pod insertion (cm). The canonical correlations analysis showed the influence of the secondary components over the primary ones. Thc path analysis showed the importante of 1000 grains weight, number of pods per plant, and number of grains per pod, presenting the largest direct effects and high phenotypic correlation with grain yield. The Mahalanobis analysis made possible to discriminate black bean genotypes regarding their degree of genetic similarity. It was also evidenced a wide genetic variability for all the evaluated characters, especially for the vegetative cycle, number of pods per plant and number of grains per pod. The use of distant genotypes in bean breeding programs, which use artificial hybridization to increase genetic variability, certainly would not lead to the narrowing of the genetic basis, since a wide genetic variability is found among black bean genotypes.