Divergência genética em genótipos de feijão-caupi (Vigna unguiculata (L.) Walp.) por descritores morfoagronômicos e variáveis multicategóricas

Abstract

Cowpea (Vigna unguiculata (L.) Walp.) Has great socioeconomic importance, mainly in the North / Northeast, constituting one of the main food components of its populations, being an important source of employment and income for small and medium producers . The genetic improvement of this species has become increasingly relevant in the countries producing this legume. Among the several methodologies used to perform the breeding, the genetic divergence has been highlighted. This analysis has helped to classify genotypes into groups and facilitated the choice of parents with characteristics desirable for the purpose of the program. Some researches have already been carried out to obtain new varieties that have desirable agronomic characteristics, however, the researches in the state of Pernambuco are being developed in an incipient way. The objective of this study was to characterize 30 cowpea genotypes of the Germplasm Bank of the Instituto Agronômico de Pernambuco (IPA), using morphoagronomic descriptors and to determine the genetic divergence between them. Qualitative and quantitative characteristics were evaluated according to the morphoagronomic descriptors proposed by Biodiversity Intenational (2007). The data were submitted to analysis of variance, obtaining the means, the variance matrix and residual covariance. The averages were purchased by the Scott-Knott test, at 5% probability, for all descriptors analyzed. With dissimilarity measures, the cluster analyzes were performed, using the multivariate technique. The coefficients of phenotypic and genotypic and environmental correlation between the pairs of characters were also estimated. There is genetic divergence among the studied genotypes, and can be used by breed improvement breeders. The quantitative characteristics contributed the most to the discrimination of the genetic divergence among the studied genotypes. The crosses between the genotypes Pitiúba x Cabeçudo, Pitiúba x Manteiga and Pitiúba x Costela de Vaca may originate new genetic combinations, because they present genetic divergence and because they have favorable agronomic characteristics. There is a high genetic component in the phenotypic expression of the evaluated traits, with a high probability of genetic gains through selection cycles for crop improvement. Among the characters evaluated, the number of pods per plant, the weight of ten pods and the weight of grains per pod are more suitable for selection of promising genotypes.