Faba bean (Vicia faba L.) is an inexpensive source of protein for both animals and humans, but the polyphenolics in the seed coat have been associated with reduced nutritional bioavailability at the protein and mineral level. There are two complimentary genes, zt-1 and zt-2, that affect the polyphenolic pathway and the presence of the homozygous recessive form of either will result in what is known as the “zero tannin” phenotype: unpigmented seed coats and white flowers. This is reminiscent of white flower/clear seed coat phenotype in pea where the A gene, a bHLH transcription factor, is responsible for the phenotype. This gene is part of the Myb-bHLH-WD40 transcription factor complex that regulates flavonoid biosynthesis. Zt-1 is likely the WD-40 gene (O’Sullivan, pers.comm.) and we hypothesize that Zt-2 is a bHLH, like in pea, or a Myb homologue.
We used available sequences of these genes from other legumes to investigate zt-1 and zt-2 in faba bean to design sequencing primers to amplify these genes in Snowbird (zt-1), Disco (zt-2) and high tannin lines (wild type). Sequences will be compared to try to identify SNPs or other indels for which specific marker assays can be developed and tested in segregating populations. These SNP markers will facilitate identification of specific zero tannin genotypes and allow breeders to know which gene is in their crossing parents and to predict whether there will be segregation or not in the offspring.