Genetic control and estimation of genetic parameters for seed-coat darkening of carioca beans

Abstract

ABSTRACT. The maintenance of the light color of the grains of carioca beans is a requirement for the development of new cultivars of common beans because it enables the storage of grains for long periods so that they may be traded at a proper opportunity. Crosses of cultivar BRSMG Madrepérola, which presents slow grain darkening, were made to 10 elite lines presenting normal darkening to obtain information about the genetic control of the trait and estimates of phenotypic and genotypic parameters. Progenies at the tegument generations F 3 and F 4 and their parents were evaluated at the locations of Santo Antônio de Goiás and Ponta Grossa at 71, 106, and 155 days of storage for seed-coat darkening using a rank of scores ranging from 1 (very light colored grains) to 5 (very dark colored grains). Genotypic and phenotypic variances and broad-sense heritabilities were estimated for each population. The segregation ratios were subjected to the chi-square test to establish the genetic control. Some populations did not present consistent patterns of genetic control, while others presented monogenic or double-recessive digenic segregation, indicating that the trait is controlled by few genes. Six segregant populations were identified 6487 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (3): 6486-6496 (2014) Seed-coat darkening of carioca beans with both low means for darkening and high expected gain under selection. Despite the strong environmental influence on the expression of the traits and the occurrence of the genotype by environment interaction, the estimates of genotypic and phenotypic parameters indicate the possibility of successful selection to develop lines with slow seed-coat darkening.

Genetic Control of Seed Coat Darkening in Common Bean Cultivars from Three Market Classes

“…This can be explained by the fact that some genotypes darken in a more accentuated way over time, a trait that cannot be observed in newly harvested seeds. In general, there was an increase in the mean values for bean seed coat darkening over storage time, as also reported in the studies of Silva et al (2014) and Alvares et al (2016).…”

“…Results from ANOVA of the two trials for phenotypic evaluation of the 17 common bean lines shown significant differences among them, regardless of seed coat storage time. The results confirm that only 45 d of storage is already sufficient to differentiate lines regarding bean seed darkening (Silva et al, 2008; Silva et al, 2014). The scores obtained at 90 and 135 d of storage were identical, and consequently, the results of ANOVA were equal in these storage periods.…”

“…After harvest, the carioca bean rapidly loses its commercial value due to chemical changes on the light‐colored seed coat, leading to depreciation of the bean seeds (dry beans) by seed coat darkening. This occurs because darker‐colored bean seeds are associated with old beans (harvested and stored for long time) and with extended cooking time and are thus rejected by consumers (Junk‐Knievel et al, 2008; Silva et al, 2008; Silva et al, 2014; Alvares et al, 2016).…”

“…There is genetic variation for seed coat darkening in common bean genotypes from pinto and carioca market classes (Junk‐Knievel et al, 2008; Silva et al, 2008; Silva et al, 2014), which creates the possibility of obtaining cultivars with slow darkening. Thus, the use of cultivars with slow seed coat darkening benefits the farmer because these cultivars will extend the possible storage period without economic losses, providing the grower with more flexibility in trading the produced beans (Silva et al, 2008).…”

“…After that, Elsadr et al (2011) indicated the presence of two genes controlling bean seed coat darkening through recessive epistasis, with one gene being responsible for darkening or lack of darkening of the bean seed coat ( J gene, with the genotype jj controlling nondarkening of the seed coat) and the other responsible for speed of darkening ( Sd gene), which may be slow ( sdsd ) or regular ( SdSd or Sdsd ). Evaluating carioca beans, Silva et al (2014) suggested that seed coat darkening is under oligogenic genetic control, with one or few genes controlling this trait. Alvares et al (2016), however, studied four carioca seeded populations and confirmed the monogenic segregation obtained by Silva et al (2008).…”