Waxy proteins in diploid, tetraploid and hexaploid wheats

Abstract

Electrophoretic analyses of waxy proteins, encoded by genes present at the Wx‐1 loci, present in several cultivars and accessions of hexaploid wheat, Triticum aestivum, have permitted the detection of null alleles at the Wx‐B1 and Wx‐D1 loci. Polymorphism at the Wx‐A1 and Wx‐B1 loci was also investigated in several accessions of tetraploid wheats, Triticum durum, Triticum dicoccoides and Triticum timopheevi, and in diploid species, Triticum urartu, Triticum boeoticum and Triticum monococcum. One null allele at the Wx‐A1 locus and three polymorphic alleles at Wx‐B1 locus were detected in T. durum; a new allele at one of the two waxy loci was identified in the tetraploid wheat T. timopheevi; no polymorphism was detected in diploid species. Polymerase chain reaction techniques made possible the detection of further polymorphism existing at the Wx‐1 loci and the reason for the lack of expression of the null genotypes to be investigated. The null forms detected at each locus have been used to produce complete sets of partial and total waxy lines in durum and bread wheat.

Functionality of native tetraploid wheat starches: Effects of waxy loci alleles and amylose concentration in blends

“…They suggested "No improvement in pasta quality should be expected if the waxy character is introduced in durum wheat." Urbano et al (2002), using both protein-and DNAbased assays, detected one null allele at the Wx-A1 locus and three different null alleles at the Wx-B1 locus of T. turgidum var. durum, but they reported no effects on amylose content or functionality.…”

DNA Markers for Identifying waxy Mutations and Improving Noodle Quality in Wheat

“…Several spontaneous mutations caused by different mechanisms than those described above have been identified in Wx-B1 10,24 and -D1 10,21 alleles. Since these mutations were not found in multiple cultivars, they may have arisen relatively recently.…”

Genetic variability for waxy genes in Argentinean bread wheat germplasm

“…Moreover, the polyploid nature of bread wheat and the high homology between A, B and D genomes, are difficult issues to overcome in the development of single-locus allele specific markers because of the always latent possibility of coamplifying homologous alleles. This is the case of markers for waxy genes developed by Briney et al (1998), McLauchlan et al (2001), Nakamura et al (2002) and Urbano et al (2002).…”

“…The lack of variability observed in the Wx-D1 locus in comparison with Wx-A1 and Wx-B1 loci agreed with previous data (Graybosh et al 1998). Urbano et al (2002) expressed that waxy protein polymorphism in wheat is not very high, especially when compared with other group of proteins, such as storage proteins of wheat kernels. A possible explanation could be that most of the initial characterization studies of waxy proteins in wheat were performed by SDS PAGE of GBSSI proteins from starch granules, and with this technology small differences between proteins might be underestimated.…”

“…Around the world several wheat collections have been characterized searching for null waxy proteins by 1D or 2D SDS-PAGE (Rodríguez-Quijano et al 1998;Demeke et al 2000;Urbano et al 2002) and PCR markers (Briney et al 1998;Boggini et al 2001;Nakamura et al 2002;Urbano et al 2002). In wheat, PCR markers can co-amplify two or three waxy genes simultaneously making difficult its use in marker-assisted selection (MAS); this is the case of PCR markers developed by Briney et al (1998), McLauchlan et al (2001), Nakamura et al (2002), Urbano et al (2002). Therefore, the development of single-locus allele specific markers for waxy null alleles is a desirable goal for MAS.…”