Genetic divergence and selection of bean cultivars of different grain types based on physical traits

Genetic divergence analysis and combined selection for various physical grain traits are unprecedented for common bean cultivars. The objectives of this study were to examine the genetic variability of common bean cultivars for 12 physical grain traits; study the correlations between these traits; analyze the genetic divergence; and select superior common bean cultivars. Two experiments were carried out in 2019 in which 22 common bean cultivars of different grain types were evaluated. Significant effects of genotype, grain type and genotype x environment interaction were obtained for all physical grain traits, indicating the existence of genetic variability. High correlations were observed between grain length and width (r = 0.844), normal grains and uptake (r = 0.796) and uptake and cooking time (r = -0.651). The L* (grain lightness) and a* (variation between green and red hue) values had a greater contribution to the differentiation between common bean cultivars. Four and three groups of cultivars were formed by the analyses of canonical variables and unweighted pair group method with arithmetic mean, respectively. Both cluster analyses are efficient in separating the cultivars into homogeneous groups based on the L* and a* values, although the canonical variables analysis provides more detailed information. The cranberry bean cultivars BRS Executivo, BRS MG Realce and Hooter and the black bean cultivars IPR Tiziu, BRS Esteio and Guapo Brilhante have superior physical grain traits and will thus be selected by the breeding program.