The effects of post-anthesis shading on starch granule size distribution and viscosity parameters in waxy and non-waxy soft wheat

To clarify the effects of post-anthesis low light on grain yield and starch quality of waxy and non-waxy soft wheat, a field experiment was conducted from 2023 to 2025. Two wheat cultivars, Jinuo 2 (waxy soft wheat) and Quanmai 725 (non-waxy soft wheat), were employed as test materials, and four shading treatments (no shading, 10% shading, 20% shading, and 30% shading) were applied after anthesis. The regulatory effects of different shading intensities on wheat yield, grain quality, starch granule size distribution and starch viscosity properties were systematically analysed. The results showed that post-anthesis low light stress significantly reduced the grain number per spike, 1 000-grain weight and grain yield, while increasing the protein content, wet gluten content and sedimentation value of wheat grains. Under low light stress, the volume and surface area proportions of A-type starch granules increased, while those of B-type starch granules decreased. Under the same shading condition, Jinuo 2 exhibited a higher proportion of B-type starch granules and a lower proportion of A-type starch granules than Quanmai 725. With increasing shading intensity, the peak, trough and final viscosities, as well as the breakdown and setback values, of grain starch decreased continuously, and all viscosity parameters of Quanmai 725 were significantly higher than those of Jinuo 2. Furthermore, post-anthesis low light reduced the onset, peak and conclusion gelatinisation temperatures and increased gelatinisation enthalpy. Quanmai 725 had higher gelatinisation temperatures, whereas Jinuo 2 possessed higher gelatinisation enthalpy. Correlation analysis indicated that the volume distribution of B-type starch granules (≤ 10 μm) was significantly positively correlated with starch viscosity parameters, while A-type starch granules (> 10 μm) showed a significant negative correlation. In conclusion, post-anthesis low light reduces the yield and the proportion of B-type starch granules, increases the proportion of A-type starch granules, decreases starch pasting viscosity and elevates gelatinisation enthalpy in both soft wheat cultivars. Compared with Quanmai 725, Jinuo 2 is more sensitive to post-anthesis low light stress in terms of starch granule distribution characteristics.