Starch Component Characteristics and Physicochemical Properties in Wheat Grains with Different Amylose Contents in Relation to Low Light after Anthesis

The effect of low light on the characteristics and physicochemical properties of wheat starch components after anthesis were investigated using wheat cultivars with different amylose contents, Lunxuan 987 and Nongdanuo 50222, which were blocked to allow only 60% photosynthetic active radiation during the total grain filling (S1), early grain filling (1-10 DAA, S2), middle grain filling (11-20 DAA, S3), and later grain filling (21-30 DAA, S4) stages. The control was not shaded (CK). The results showed that the starch content, amylose, amylopectin, and relative crystallinity significantly decreased under low light conditions after anthesis. The amylose/amylopectin ratio increased in Lunxuan 987 at S2 and S3, while it decreased overall in Nongdanuo 50222. The volume and proportion of surface B-granules in Lunxuan 987 increased at S2 and S4, while those of Nongdanuo 50222 increased at each low light stage. The peak viscosity, trough viscosity, breakdown value, and enthalpy of Lunxuan 987 starch improved at S1 and S4, while the above indices in Nongdanuo 50222 decreased and were significantly higher than in Lunxuan 987. Nongdanuo 50222 showed a lower starch yield, higher B-granule volume, surface area proportion, and crystallinity than Lunxuan 987, and showed significant differences in all pasting and thermal parameters compared to Lunxuan 987. There were significant correlations between wheat endosperm starch components and their physicochemical properties, indicating that the effects of low light after anthesis on wheat starch components indirectly affected the physicochemical properties.