The effects of top-dressing to basal nitrogen ratios on grain yield and quality of winter wheat under heat stresses during grain Filling
不同氮肥基追比例对高温胁迫下小麦籽粒产量和品质的影响

In order to investigate the effect of nitrogen regimes on grain yield and quality under heat stresses during grain filling, we investigated three winter wheat cultivars with strong gluten at differential ratio of top-dressing to basal nitrogen fertilization. Three wheat cultivars, Jimai 20, Yannong 19 and Gaomai 8901, were subjected to heat stresses during the last half of grain filling stage. Grain weight, grain yield, and grain quality (protein composition) were carefully examined. Increased ratio of top-dressing to basal nitrogen fertilization generally led to significant increase of 1000-grain weight, grain yield and the content of crude protein, wet gluten, gliadins, glutenins. Meanwhile, higher content of high molecular weight glutenins subunit (HMW-GS), low molecular weight glutenins subunit (LMW-GS) and the ratio of HMW-GS to LMW-GS were also noted. However, the effect of increased ratio of top-dressing to basal nitrogen fertilization on glutenin macropolymer (GMP) content and GMP particle size distribution (weighted average surface area and weighted average volume) was found to be not consistent. While higher ratio of top-dressing to basal nitrogen fertilization elevated the GMP content and weighted average surface area and weighted average volume in Jimai20 and Yannong19, those traits from Gaomai 8901 remained nearly unaffected. Accordingly, similar tendency was observed for both dough development and dough stability time. Increased ratio of top-dressing to basal nitrogen fertilization, from 50% to 70%, resulted in remarkable decline of the ratio of amylopectin to amylose and peak viscosity, hold through, breakdown, final viscosity and setback of starch. Our findings indicated that higher ratio of top-dressing to basal nitrogen fertilization could alleviate somewhat the adverse effect of heat stresses on grain weight and protein quality (farinograph parameters especially). However, such an improvement was achieved on the cost of worsening starch quality (RVA index), although the degrees of those effects always fluctuates with different cultivars.