Molecular characterization of new waxy mutants identified in bread and durum wheat

Recently, electrophoretic analyses of waxy proteins in several hexaploid and tetraploid wheat accessions from worldwide collections have permitted the identification of new variants at the waxy loci, including allelic forms with different mobilities and partial null types. In this paper, the molecular characterization of mutated waxy loci in four bread wheat cultivars (two lacking the Wx-B1 and two lacking the Wx-D1 protein, respectively) and in four durum wheat cultivars (one lacking Wx-A1 and the remainder with Wx-B1 proteins showing different electrophoretic mobilities) was conducted by means of PCR, Southern and DNA sequence analyses. Three primer pairs were developed that identified six of the above-mentioned mutations and allowed their molecular description, providing a useful tool for further germplasm screening or marker assisted progeny selection in breeding programs involving the newly identified material. We have found that a complete gene deletion is responsible for a null allele at the Wx-B1 locus in one bread wheat line, whereas sequencing of the corresponding fragments showed a 724 bp deletion in the Wx-D1 locus in one line of bread wheat and an insertion of 89 bp in the Wx-A1 locus in one line of durum wheat, respectively. In addition, nucleotide substitutions and various insertions/deletions ranging from 3 to 30 bp were detected in the PCR fragments of one durum wheat line with a Wx-B1 protein with a different electrophoretic mobility. A fourth primer set, specific for this mutation, was consequently derived.