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

Abstract

Common bean (Phaseolus vulgaris L.) cultivars with slow seed coat darkening benefit the growers by extending the seed storage period without losses in commercial quality. Seed coat darkening in pinto and carioca seeded common bean is controlled by recessive genes, but it is not known whether these genes are different or not. The objectives of this study were (i) to verify if the gene that controls seed coat darkening in common bean cultivars from different market classes is the same, and (ii) to evaluate the efficiency of the simple sequence repeat (SSR) marker Pvsd‐1158 and the single nucleotide polymorphism (SNP) marker PvbHLHp12804 linked to the Sd gene in identifying carioca and mulatinho seeded lines contrasting for seed coat darkening. Seventeen lines were used for genotypic and phenotypic evaluations in two trials, and F2:3 progenies obtained from crosses between one pinto bean line (Sd gene) and two carioca lines that have slow seed coat darkening were used in segregation tests. The result of the two markers was identical and shown 87.5% coincidence with phenotypic data. Only two lines, CNFM 11940 (mulatinho) and TAA Dama (carioca), exhibited slow seed coat darkening and marker alleles related to regular darkening. Therefore, there was recombination between the markers and the Sd gene, or there is another gene causing slow seed coat darkening in these lines. All F2:3 progenies exhibited slow seed coat darkening, indicating that there was no segregation. The two markers are efficient for assisted selection. Results of the genotypic evaluations and the segregation test indicating that the same gene (Sd) is responsible for seed coat darkening in pinto and carioca beans.