Abstract
ABSTRACT Seed color, brightness and texture are important aspects for the consumption of immature beans. This study aimed to estimate the phenotypic variability among thirty cowpea genotypes for immature seed harvesting, in order to guide breeding programs. The experiment was carried out in a randomized blocks design, with three replications. The evaluated traits were immature seeds yield, pods and dry seeds production, number of immature pods, 100-immature seeds weight, immature pods length, number of seeds per immature pod, cooking time, harvesting period of immature pods, seed color, pod color, plant growth habit, opening of immature pods, seed threshing from immature pods, cultivation value and seed browning after threshing. Anova and three clustering methods were applied: UPGMA using the Jaccard coefficient of similarity; modified Tocher method based on the Gower algorithm; and k-means. All the analyses were performed based on the variable means of experiments evaluated in six environments. A statistically significant phenotypic variability was observed among all the quantitative traits. Discrepancies occurred in the accessions grouping and number of clusters. The accession BRS Acauã, in one group, and P508 and PCCR3F6L15, in other groups, showed a good quality for immature grain harvesting, were consistently grouped into different clusters and are recommended for use as parents in the development of new cultivars.
Highlights
In northeastern Brazil, cowpea [Vigna unguiculata (L.) Walp] is mainly grown for dry seed production, the commercialization of immature seeds is expressive
The means of the cowpea genotypes were subjected to three cluster analyses: unweighted pair group method with arithmetic mean (UPGMA), using the NTSYs software (Rohlf 2000), considering the Jaccard similarity coefficient with nine quantitative variables categorized into five classes; presence (1) or absence (0) of traits evaluated in each class using the modified Tocher method based on the Gower algorithm with the Genes software (Cruz 2016); k-means clustering with qualitative data transformed to √x + 1, considering the formation of three groups
The genotypes differed with regard to the opening of immature pods and seed release from immature pods by manual threshing
Summary
In northeastern Brazil, cowpea [Vigna unguiculata (L.) Walp] is mainly grown for dry seed production, the commercialization of immature seeds is expressive. Immature seeds are obtained from pods around maturity, i.e., immediately before or shortly after the plant stops accumulating photosynthates and begins the natural dehydration process, which occurs with. Cowpea has a high genetic variability for almost all morphological and agronomic traits, though little has been investigated in this regard (Teixeira et al 2010). Information on the phenotypic variability of cowpea germplasm and on how much of it is due to genetic differences is fundamental in breeding programs (Cruz et al 2004). According to Cruz et al (2004), diversity denotes the genetic distance within species, populations or accessions measured through morphological, agronomic, biochemical, physiological and molecular traits
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