Appropriate nitrogen fertilization is essential for improving grain yield and starch quality, while reducing N fertilizer costs. The starch physicochemical properties of two waxy maize hybrids, namely, Suyunuo5 (SYN5) and Yunuo7 (YN7), under N rates of 0 (zero N application [N0]), 150 (low N rate [LN]), 225 (moderate N rate [MN]), and 300 (high N rate [HN]) kg ha -1 are elucidated. Grain starch content initially increases, peaks at MN, and decreases as N rate is increased. N fertilization reduces the starch granule size of YN7. The starch granule size of SYN5 increases under MN. SYN5 exhibits high short/long amylopectin chain ratios under LN and MN. The short/long amylopectin chain ratio of YN7 is unaffected by MN but is increases by LN and HN. The swelling power of YN7 is similar among different N levels, whereas that of SYN5 increases under N fertilization. N fertilization changes starch pasting and thermal properties. Starch with large granules exhibit high trough, final, and setback viscosities and gelatinization temperatures. Starch with high long-chain ratios is susceptible to retrogradation. In conclusion, appropriate N application (225 kg ha -1 for SYN5 and 150 kg ha -1 for YN7) favors starch accumulation, and starch has high viscosity and low retrogradation tendency.

No abstract

No abstract

Background and objectives The low sunlight from June to July caused by cloudy weather in Southern China has a detrimental influence on the grain yield and quality of spring maize because this period overlaps with the grain filling stage. A field trial was conducted to study the effects of postsilking shading (30% and 50% light deprivation defined as moderate sunlight [MS] and severe shading [SS], respectively, and with plants under natural sunlight as the control) on grain weight, nutrient contents, pasting, and thermal properties in 2016–2017. Zhengdan958 (ZD958) and Suyu30 (SY30) were used as materials. Findings MS and SS reduced the grain weight by 26.7% and 42.4% for ZD958 and by 17.4% and 25.7% for SY30 in 2016, respectively. In 2017, the decrease was 6.8% and 2.7% for ZD958 and SY30, respectively, and no difference was observed between MS and SS. Shading reduced the starch content and increased the protein content, and the effects were severe when a large amount of sunlight was deprived. SS increased the starch granule size in both varieties and years. MS resulted in an increase in 2016, but no increase was observed in 2017. Peak, trough, and breakdown viscosities decreased under shading. Similar reductions were generally observed between MS and SS. Shading exerted minimal effects on gelatinization and retrogradation temperatures, but the gelatinization enthalpy and peak height index gradually decreased with decreasing sunlight intensity. The retrogradation percentage increased under shading, and this increment was similar for MS and SS in 2016 and gradually intensified with increasing light deprivation in 2017. Conclusions Shading reduced starch and amylose contents and increased protein contents and starch granule size. These effects induced low peak and breakdown viscosities and high retrogradation percentage. The high viscosities and low retrograde of SY30 indicated that it has better grain quality than ZD958. Significance and novelty Shading deteriorates flour viscosity and increases the retrogradation tendency by reducing grain starch content and increasing protein content and starch granule size.

No abstract