Allelic Variants at the Psy‐A1and Psy‐B1Loci in Durum Wheat and Their Associations with Grain Yellowness

Phytoene synthase (PSY) genes are involved in the biosynthesis of carotenoid pigments in durum wheat [Triticum turgidumL. subsp durum(Desf.) Husn.], significantly influencing grain yellowness. This study was conducted to identify new allelic variants at the Psy‐A1and Psy‐B1loci in durum wheat, and to evaluate the applicability of functional markers developed from common wheat (Triticum aestivumL.) for durum wheat breeding. Two new allelic variants, Psy‐A1dand Psy‐A1e, were identified at the Psy‐A1locus, and both the codominant markers YP7Aand YP7A‐2can be used to discriminate the two haplotypes, yielding 194‐ and 231‐bp polymerase chain reaction (PCR) products with YP7Aand 1001‐ and 1684‐bp fragments with YP7A‐2, respectively. At the Psy‐B1locus, three allelic variants were identified. Psy‐B1ewas also found in common wheat, whereas Psy‐B1fand Psy‐B1gwere detected only in durum wheat. The codominant marker YP7B‐1can be used to distinguish Psy‐B1fand Psy‐B1g, generating 151‐ and 153‐bp PCR fragments, respectively, and the dominant marker YP7B‐4was specific to haplotype Psy‐B1e, producing a 717‐bp PCR product. In a set of 100 CIMMYT durum wheat lines with widely variable grain yellowness, the frequencies of Psy‐A1d, Psy‐A1e, Psy‐B1e, Psy‐B1f, and Psy‐B1gwere 99, 1, 0, 67, and 33%, respectively, and the genotype Psy‐B1fshowed a significant association with higher grain yellowness, whereas the presence of Psy‐B1gled to lower yellowness. A phylogenetic tree generated from the gene sequences of the allelic variants at Psy‐A1and Psy‐B1loci indicated two parallel lineages of durum–common wheat, suggesting that more than one tetraploid T. turgidumL. subsp. dicoccon(Schrank) Thell. genotypes were involved in the origin of common wheat. Our results suggested that Psy‐B1fshould be paid more attention in durum breeding programs for its association with elevated grain yellowness.