Agro-morphological characterization and genetic divergence assessment in bush snap bean genotypes 1

摘要

The characterization and identification of genetically divergent parents for crosses are important tasks in snap bean breeding programs, for a greater availability of cultivars to growers. This study aimed at characterizing bush snap bean genotypes originating from different countries; assessing the genetic divergence between the genotypes and the genetic variability extent, concerning 12 agro-morphological traits; and determining the relative importance of these traits for the genetic divergence. The experiment was conducted in a randomized complete block design, with 29 genotypes and four replications. The UPGMA and Tocher optimization methods, both based on the generalized distance of Mahalanobis, and the canonical variables method were used to analyze the genetic divergence. The genotypes exhibited a wide range of genetic variability for the agro-morphological traits evaluated, mainly for 100-seed weight, aspect and yield of commercial pods, plant height at harvest and pod weight. A high genetic divergence was detected between the genotypes, in which the 100-seed weight and aspect of commercial pods were the most important traits for clustering. Some genotypes own desirable characteristics for these and other traits, given the favorable genetic associations between traits. The snap bean genotypes originated from different countries tended to cluster together, indicating that similar germplasm is shared among different countries, thus suggesting a strong trans-national seed exchange.