Cotyledon color is one of the important indices for identifying faba bean variety purity and measuring processing quality. Therefore, an in-depth study of the genetic mechanism of cotyledon color is vital for promoting faba bean industry development. We used the yellow cotyledon variety Qingcan 16 and the green cotyledon variety Qingcan 17 as parent plants to construct hybrid combinations. F1-, F2-, BC1F1-, and BC2F1-generation single-plant cotyledon colors were counted to clarify cotyledon color inheritance. F2-generation individuals were genotyped using ddRAD-Seq to construct a genetic linkage map and identify QTLs for cotyledon color. Green cotyledons were controlled by one pair of recessive nuclear genes. Using the screened 1991 SNP markers, a high-density linkage map was constructed, with a coverage length of 1476.95 cM and an average map distance of 0.96 cM. The green cotyledon trait was located using WinQTL Cart, and a vfGC candidate interval explaining 34.30 to 49.40% of the phenotypic variation was identified at LG02 (101.952 cM to 115.493 cM) and at LOD = 16.0, corresponding to chr1L 1,077,051,302 bp to 1,636,400,339 bp (559.35 Mb). The above interval contained 2021 genes, 20 of which were involved in photosynthesis, but no SGR or genes with similar functions were identified. However, the published faba bean vfSGR was located within the vfGC candidate interval, confirming that our localization interval was reliable. The above findings provided further clues for the fine localization of genes regulating green cotyledons and the development of molecular linked markers in faba bean.
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