Structure and properties of amylopectin isolated from endosperm starch of low-amylose bread wheat

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Large A-type endosperm starch granules were isolated from near-isogenic waxy and non-waxy lines and low-amylose mutant lines of bread wheat with a common genetic background. The amylose contents of A-type starch ranged from 2.6% to 23.6%. Amylopectin was isolated by concanavalin A (Con A) precipitation from the isolated starch. The λ_<max> and blue values at 680 nm of the iodine-amylopectin complex were not significantly different among the isolated amylopectins, indicating that amylopectins from non-waxy and low-amylose lines did not contain such long chains as amylose or extra-long chains of amylopectin affecting iodine complex properties. Chain-length distribution profiles measured by both high-performance size exclusion chromatography (HPSEC) and high-performance anion-exchange chromatography (HPAEC) showed that the amylopectin structure of these lines was indistinguishable from each other. Extra-long chains were not detected in the amylopectins by HPSEC measurement. The alleles on the Wx-D1 locus, i.e. Wx-D1a, Wx-D1d, Wx-D1f, and Wx-D1g, responsible for granule-bound starch synthase (GBSS I) biosynthesis had no influence on the properties of iodine-amylopectin complex and the chain-length distribution profiles of amylopectin.