Wx gene in diploid wheat: molecular characterization of five novel alleles from einkorn (Triticum monococcum L. ssp. monococcum) and T. urartu

The Wx gene encodes the granule-bound starch synthase I or waxy protein, which is the sole enzyme responsible for amylose synthesis in wheat seeds. Triticum urartu and einkorn (T. monococcum L. ssp. monococcum), which are related to the A genome of bread wheat, could be important sources of variation for this gene. This study evaluated the Wx gene variability in 52 accessions of these species and compared their nucleotide sequences with the Wx-A1a allele of bread wheat. The level of polymorphism found was high, although not distributed equally between the two species. Five different alleles were found in T. urartu, of which four were novel (Wx-A (u) 1b, -A (u) 1c, -A (u) 1d and -A (u) 1e). All einkorn accessions had the same allele, which was also novel and was named Wx-A (m) 1a. A comparison between the proteins deduced from the novel alleles and the Wx-A1a protein showed that there were up to 33 amino acid changes in both the transit peptide and the mature protein. These results showed that these species, especially T. urartu, are a potential source of novel waxy variants.