Agro-morphological characterization and genetic divergence assessment in bush snap bean genotypes1

Abstract

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.

Characterization, Genetic Diversity, and Clustering of Common Bean (Phaseolus vulgaris L.) ‎Accessions Based on Seed Yield and Related Traits ‎

“…The ratio between genotypic coefficient of variation and environmental coefficient of variation (GCV/ECV) was larger than the unit for all traits, with high estimates, therefore, it is additional evidence that the traits are promising for successful selection (Correa et al, 2015 andVaz et al, 2017). The high genetic variations are probably due to the nature of the investigated genetic materials, since they are genebank germplasm, consist of landraces and advanced cultivars which widely differ in their traits.…”

“…The inter-cluster distances and the mean performance of the accessions should be considered together as the genetically divergent parents may not have the best combining ability unless they also have good performance of the traits being improved (Vaz et al, 2017) . Consequently, the crossing between the best performing genotypes from diverse clusters is recommended.…”

“…Our results agree with those obtained by Carvalho et al (2016) since he found that 24 accessions of common bean were grouped into three groups by Tocher optimization method or UPGMA method. Also, Vaz et al (2017) reported that four groups were formed for 29 genotypes of the bush snap bean by either grouping methods.…”

Seed production of bush snap beans genotypes in conventional and organic systems

“…Evaluating only the conventional system, in the Cerrado region, Vaz et al (2017) found yield ranging from 1,536 to 3,398 kg ha -1 . The high incidence and controlling difficulty of Diabrotica speciosa in the initial phase, and of Bemisia tabaci, from the flowering stage onwards, may have been the main responsibles for the low yield, specially in the conventional system, despite the adopted controlling measures using recommended pesticides.…”

“…These have contributed to the expansion of snap beans crop in several regions of Brazil, with it standing out as a good low operational cost option for Fall/ Winter in irrigated areas, since they enable the mechanization of most cultivation operations. Moreover, these cultivars produce good quality pods, which in turn has led to the greater demand for this group by producers (Francelino et al, 2011;Andrade et al, 2017;Peixoto & Cardoso, 2016;Vaz et al, 2017).…”