Relative variation in β-glucan components in the oat grain (Avena sativa) during development and between varieties

Abstract

Oat β-glucan provides health-benefitting properties, with the ratio of subunit trimers to tetramers the main identified molecular difference between this and other grain-derived β-glucans. This ratio change causes alterations in the viscosity and gelling potential of the β-glucan, which in turn affects cholesterol uptake and conversion. This study compares both the physical variables (grain dry weight, width, length) and the ratio and total yield of trimer and tetramer units in developing winter oat (Mascani) grain over two harvest years. Results found the grain weights and widths correlated through the development stages, with length increasing earlier in the development, matching developmental studies in wheat grains. Within the total β-glucan fraction, the yield followed the trend for grain weight, with the β-glucan ratio between the composite subunits highly conserved from the beginning of grain formation. β-Glucan yields were shown not to differ between grains taken from locations across the whorls of the panicle or between the grain types (primary or secondary) within the spikelets, showing composition consistency despite developmental differences. To widen the significance of this work, the yields and ratios of β-glucan trimer and tetramer were also assessed in 46 different mature oat grain varieties (excluding Mascani). These were found to have a reduced trimer:tetramer ratio correlation (R² = 0.84; in Mascani-only studies R² = 0.99–1), showing limited diversity between accessions. All spring oat varieties had a lower trimer:tetramer ratio than seen in the Mascani grain initial studies, a positive breeding attribute. A further correlation was seen between trimer:tetramer ratios, grain size and nitrogen, with lower β-glucan ratios associated with larger grains and lower nitrogen content. Collectively, findings from this study identify useful trait variation for future breeding programme selection considering enhanced health benefits.