Chromosomal location and molecular characterization of three grain hardness genes in Agropyron cristatum

Grain hardness is an important characteristic of wheat quality. This trait is mainly related to the variation in, and the presence of, puroindolines (Pina and Pinb genes), and, to a lesser extent, the grain softness protein (Gsp-1) gene. The current study evaluated the allelic variability levels of these three genes in 12 diploid lines from Agropyron cristatum, a species from the tertiary wheat genepool. Along with their chromosomal locations, the molecular characterizations of the main allelic variants were found and their phylogenetic relationships with wheat genomes were determined. The hardness (Ha) locus, which includes the Pina, Pinb and Gsp-1 genes, was physically mapped on the short arm of chromosome 5P of A. cristatum. This conservation of synteny in homeologous group 5 suggests that the genes isolated in the present study are orthologues of the wheat Pina, Pinb and Gsp-1 genes. The identified polymorphisms resulted in three alleles, two for the Pinb and Gsp-1 genes, but only one allele for the Pina gene. Diverse changes were detected in the deduced mature proteins of these alleles, which could influence their hardness characteristics. The Pina, Pinb and Gsp-1 genes from diploid A. cristatum might be good sources of genetic variability that could extend the range of wheat grain textures in parallel with the introgression of other useful agronomic traits.