Identification and Cloning of the TdBa Controlling Black Awn Color in Durum Wheat (triticum Durum Desf.)

Melanins are a class of dark pigments widely distributed among living organisms. In cereal crops, the black husk-pericarp trait arises from melanin accumulation. The durum wheat (Triticum turgidum L. var. durum Desf.) cultivar Ofanto (Oft) exhibits black awns beginning at the soft dough stage. To identify the genetic loci associated with awn color, we analyzed an F2 population derived from a cross between Oft (black awn) and Langdon (LDN, yellow awn). Genetic mapping revealed a single dominant black awn gene, TdBa, located within an approximately 4.38 Mb interval on the short arm of chromosome 1AS. Among the 34 annotated genes located within this interval, TRITD1Av1G000090, which encodes amino acid transporters homologous to the rice black hull gene OsBh4 and barley black husk/pericarp gene HvBlp, was identified as a candidate gene based on sequence, expression, and gene function prediction analyses. In contrast to its homologous genes OsBh4 and HvBlp, TdBa causes only black awn in wheat. The role of TRITD1Av1G000090 in awn coloration was subsequently confirmed through transgenic assays.