Influence of Mutant Wx-D1f Allele on Synthesis of Amylose and Extra-Long Chains of Amylopectin in Wheat (Triticum aestivum L.)

Waxy wheat lines carrying null alleles at the loci Wx-A1 and Wx-B1 and a mutated Wx-D1 allele (Wx-D1f) generate unique pasting curves on a Rapid Visco Analyzer. The initial pasting temperature, peak viscosity, and final viscosity are found to not differ markedly between waxy wheat carrying Wx-D1b and waxy wheat carrying Wx-D1f, but the hot-paste viscosity is more stable in the case of waxy wheat carrying Wx-D1f. The study seeks to determine the cause for this unique starch property. Whereas amylopectin chain-length distribution is similar in wheat lines #211 (Wx-A1b, Wx-B1b, Wx-D1a) and #234 (Wx-A1b, Wx-B1b, Wx-D1f), #234 contained 7.0% amylose and 1.3% extra-long chains (ELCs) of amylopectin, levels corresponding to 1/3 and 2/3 of the content of amylose and ELCs of amylopectin in #211, respectively. Moreover, #234 contains a small-chain amylose not detected in #211. Therefore, this study concludes that the unique starch characteristics of waxy wheat carrying Wx-D1f may be due to the relatively high quantity of ELCs of amylopectin and/or the low-molecular-weight amylose.