Understanding the formation of starch structure during grain development in two wheat cultivars with different...

Apart from starch content, structure is also vital for the eating and nutritional qualities of final products. The study investigated how the starch structure changed during grain filling period using two wheat cultivars with different filling rate. The starch biosynthesis during grain filling was not at uniform speed and most of starches were synthesized before 19 DAF. The starch structure establishment was latter than starch accumulation, but the structure formed at early stage of grain filling was highly related to the final one. The process of starch biosynthesis was closely accompanied by the elongation of amylose chains, increase on branch numbers, B-type granule number and expansion of A-type granule. Further analysis on expression profiles of key genes involved in starch biosynthesis demonstrated that different genes exhibited varying responsiveness to the filling rate, and the resulting imbalance in gene expression may underlie the observed structural differences. Faster filling promoted earlier activation of starch-biosynthesis genes, particularly GBSSI, leading to preferential elongation of amylose chains, higher crystallinity, and more B-type granules. The results will provide new insights to understanding the formation starch structure during grain filling, which may benefit future research on management and breeding.