The effect of mutant genes at the r, rb, rug3, rug4, rug5 and lam loci on the granular structure and physico-chemical properties of pea seed starch

The granular structure and gelatinisation properties of starches from a ran ge of pea seed mutants were studied. Genes which affect the supply of subst rate during starch synthesis (rb, rug3, rug4) affected the total crystallin ity and possibly increased the content of A polymorphs in the starch. Conve rsely, genes directly affecting the synthesis of starch polymers (r, rug5, lam) increased the content of B polymorphs, but had a minimal effect on tot al crystallinity. During gelatinisation, starches from the I rb, rug3, rug4 and lam mutants had narrow endothermic peaks which were similar to starch from the wild-type, although all the starches had different peak temperatur es and enthalpy changes. Starches from r and rug5 mutants were very differe nt to all other starches, having a very wide transition during gelatinisati on. In addition, the amylopectin in starch from these mutants had altered c hain lengths for those parts of the polymer which form the ordered structur es in the granule. (C) 1999 Elsevier Science Ltd. All rights reserved.