Waxy and Low-Amylose Mutants of Bread Wheat (Triticum aestivum L.) and their Starch, Flour and Grain Properties

抄録

Bread wheat has three waxy proteins (= granule-bound starch synthase I, GBSSI), which are genetically controlled by three homoeologous loci, Wx-A1, Wx-B1 and Wx-D1. Several mutant lines with waxy and low-amylose endosperm were induced from cv. Kanto 107, which has two null Wx-A1b and Wx-B1b alleles and a functional Wx-D1a allele. Starch was isolated from their grain and its amylose content, chain-length distribution profiles and thermal properties were determined. Waxy mutant lines, K107Wx1 and K107Wx2, had a new null allele named Wx-D1d on the Wx-D1 locus; a low-amylose mutant line, K107Afpp4, had a new less functional allele named Wx-D1g on the locus. Paste viscosity is markedly suppressed in waxy flour when pasting properties are measured in water using a Rapid Visco Analyzer because waxy starch swells greatly and would disintegrate at a lower temperature where α-amylase is still active. Flour yield of the waxy mutant lines was lower than that of Kanto 107 because the waxy lines had decreased starch content and increased fat and β-glucan contents more than the wild type. Possible uses of the mutant lines were described from the standpoint of starch science and genetic resource.