Abstract
Three genes associated with the seed coat color in a TU/Musica RIL population were located on a genetic map, and two candidate genes proposed to control black seed coat in the TU genotype were characterized. Seed coat color is an important characteristic of common bean (Phaseolus vulgaris L.) associated with the marketability of dry bean cultivars, quality and nutritional characteristics of seed, as well as response to pathogens. In this study, the genetic control of seed coat color in a recombinant inbred line population (175 lines) obtained from the cross 'TU' × 'Musica' was investigated. Phenotypic segregation fitted 1:1 for white vs. nonwhite, and 3:1 for brown versus black, indicating the involvement of three independent genes, one controlling white color and two (with epistatic interaction) controlling black color. Using a genetic map built with 842 SNPs, the gene responsible for the white seed coat was mapped on the linkage group Pv07, in the position previously described for the P gene. For the black seed coat phenotype, two genes were mapped to the beginning of chromosomes Pv06 and Pv08, in the positions estimated for the V gene and the complex C locus, respectively, by classical studies. The involvement of these two genomic regions was verified through two crosses between three selected RILs exhibiting complementary and dominant inheritance, in which the TU alleles for both genes resulted in a black phenotype. Two genes involved in the anthocyanin biosynthesis pathway were proposed as candidate genes: Phvul.006G018800 encoding a flavonoid 3'5'hydroxylase and Phvul.008G038400 encoding MYB113 transcription factor. These findings add knowledge to the complex network of genes controlling seed coat color in common bean as well as providing genetic markers to be used in future genetic analysis or plant breeding.
Highlights
Common bean (Phaseolus vulgaris L.) is one of the most important grain legumes and is cultivated widely throughout the world (FAOSTAT 2020)
The observed segregation fitted an expected Mendelian ratio of 1 (89): 1 (86) (χ2 = 0.05; p = 0.82), suggesting genetic control based on a single gene for the white seed coat trait
The final version of the TUM linkage map contained 842 highly informative Single nucleotide polymorphisms (SNPs) mapped to 13 linkage groups (LGs) corresponding to the 11 bean chromosomes, with chromosomes Pv04 and Pv05 divided into two blocks (Table S1, Figure S1)
Summary
Common bean (Phaseolus vulgaris L.) is one of the most important grain legumes and is cultivated widely throughout the world (FAOSTAT 2020). Beans can be consumed as immature pods (snap or green beans) or as mature seeds after re-hydration and cooking (dry beans). Organization of the United Nations (FAO) estimates, world production of dry beans for the year 2019 was 28.9 million tons (FAOSTAT 2020). Bean seeds exhibit wide phenotypic diversity, including variations in size, shape, and coat color, leading to many market classes. Within seed coat color variation there is a wide spectrum of solid colors (white, cream, yellow, brown, red, purple, and black) of different intensities, as well as patterns combining different colors (e.g., bicolor, mottled, and spotted) (Voysest 2000)
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