The influence of genotype and environment on arabinoxylans and phenolics of wheat grains
L. COPELAND (1), M. Al-Fadly (1). (1) University of Sydney, Sydney, Australia
Foods prepared from whole grains are associated with health benefits, which have been attributed in part to the presence of arabinoxylans and phenolic antioxidants. These grain constituents are closely associated in cereal cell walls but their abundance and speciation vary considerably. The present study assesses the relative contributions of genotype and environment to variability of arabinoxylans and phenolics in wheat (<i>Triticum aestivum</i> L.) grains. Total, water-extractable (WE) and water-unextractable (WU) arabinoxylan (AX) content, and total, free, conjugated and bound phenolics, were determined in wholemeal flour from three commercial Australian wheat varieties that were grown in two years across 13 locations. The mean of total AX content in the flour ranged from 2.9% to 6.6%, of which WU-AX accounted for 2.8% to 6.5%. For the grain samples used in this study, genotype contributed about 75% of the variability in total AX and WU-AX content, indicating a substantial degree of heritability of these characteristics. Genotype, growing location and year, and their interactions, all contributed significantly to differences in the amounts of total, bound, conjugated and free phenolic acids, which may explain the considerable variability in these grain constituents. Conditions at the growing locations had differential effects on the content and speciation of phenolics, consistent with genotype x environment interactions. Phenolic acids derived from cinnamic acid (p-coumaric, caffeic and ferulic acids) were mostly bound to cell wall components, whereas benzoate-derived phenolics (p-hydroxybenzoate, vanillic and syringic acids) occurred mostly as soluble conjugates, although there were also significant amounts of bound forms present. The cinnamic acid-derived sinapic acid was an exception, being present mostly as a soluble conjugate.
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