To achieve superior rice-grain quality, more emphasis has been placed on the genetic diversity of breeding programs, although this improvement could be seriously restricted in the absence of comparable agricultural management practices. Nitrogen (N) application and planting density are two important agronomic practices influencing rice growth, yield, and grain quality. This study investigated the four main aspects of rice-grain quality, namely, milling (brown-rice, milled-rice, and head-rice percentage), appearance (length/width ratio, chalky-kernel percentage, and chalkiness), nutrition (protein content), and cooking and eating quality (apparent amylose content, gel consistency, and pasting viscosities) of two rice cultivars (Shendao 47 and Jingyou 586) under four N rates (0, 140, 180, and 220 kg ha−1), and three planting densities (25 × 104, 16.7 × 104, and 12.5 × 104 hills ha−1) in a field trial from 2015 to 2016. The four main aspects of rice-grain quality were significantly influenced by cultivar. Several aspects were affected by the interactions of N rate and cultivar. No significant interaction between N rate and plating density was detected for all grain-quality parameters. A higher N rate increased the percentages of brown rice and head rice, chalky-kernel percentage, and setback and peak time values, but reduced the length/width ratio, chalkiness, apparent amylose content, gel consistency, and peak-, trough-, and final-viscosity values. These results indicate that the N rate has a beneficial effect on milling and nutritional quality, but a detrimental effect on appearance and cooking and eating quality. Jingyou 586 and Shendao 47 had different responses to planting density in terms of grain quality. Our study indicates that low planting density for Jingyou 586, but a medium one for Shendao 47, is favorable for grain quality.

Nitrogen fertilization and planting density are two key factors that can interactively affect the grain yield of rice. Three different types of rice cultivars-inbred Shendao 47, inbred Shendao 505, and hybrid Jingyou 586-were applied to investigate the effects of the nitrogen (N) rate and planting density (D) on the aboveground biomass, harvest index, leaf photosynthetic features, grain yield, and yield components using a split-split-plot design at two sites over two continuous years. The main plots were assigned to four nitrogen fertilizer rates: 0 (N0), 140 (N1), 180 (N2), and 220 (N3) kg ha −1 N; the subplots were assigned to three planting densities: 25 × 10 4 (D1), 16.7 × 10 4 (D2), and 12.5 × 10 4 (D3) hills ha -1 , and the sub-subplots were assigned to three rice cultivars. The results showed that the grain yield had a significantly positive correlation with the stomatal conductance (Gs), net photosynthesis rate (Pn), transpiration rate (Tr), chlorophyll content (SPAD value), leaf area index (LAI), panicles per unit area, and spikelets per panicle. The N rate and planting density had significant interaction effects on grain yield, and the maximum values of Shendao 47, Shendao 505, and Jingyou 586 appeared in N3D2, N2D1, and N3D3, respectively. The higher grain yield of midsized panicle Shendao 47 was mostly ascribed to both panicles per unit area and spikelets per panicle. More panicles per unit area and spikelets per panicle primarily contributed to a larger sink capacity of small-sized panicle rice Shendao 505 and large-sized panicle rice Jingyou 586. We found that the treatments N3D2, N2D1, and N3D3 could optimize the contradiction between yield formation factors for Shendao 47, Shendao 505, and Jingyou 586, respectively. Across years and sites, the regression analysis indicated that the combinations of nitrogen fertilization of 195.6 kg ha −1 with a planting density of 22 × 10 4 hills ha −1 , 182.5 kg ha −1 with 25 × 10 4 hills ha −1 , and 220 kg ha −1 with 13.1 × 10 4 hills ha −1 are recommended for medium-, small-, and large-sized panicle rice cultivars, respectively. food habits are changing due to rising living standards, such as the increased consumption of livestock products (such as meat, eggs, and milk), which drives the increase in demand for feed grains, especially in Asia [4,5]. At present, China's area under rice cultivation is 30.3 million hectares with the total yield reaching 207.7 million tons and an average yield of 6.8 t ha −1 , which is 65% higher than that of the world average [6]. China, the world's largest rice producer, has sustainably fed 22% of the world's population using only 7% of the arable land in the world. However, in the past 10 years, increases in rice yield have been slowing down in China, and the increasing population and shortage of arable land have exerted tremendous stress on food security [7]. Therefore, to ensure food security for the growing population, improving rice productivity (production per unit area) remains a priority in China.Much emphasis has been put...

Plant architecture is an accessible approach to achieving high‐yield potential. The DENSE AND ERECT PANICLE 1 (DEP1) gene regulating panicle morphology, grain number per panicle, and nitrogen uptake and metabolism has been widely used for the breeding of high‐yield rice in northern Chinese japonica varieties. However, there has been no consensus on the genetic effects of dep1 on grain yield and quality under different genetic backgrounds and growing environments. In the present study, we developed two sets of near‐isogenic lines (NILs) of DEP1 (AKI‐dep1, AKI‐DEP1, LG5‐dep1 and LG5‐DEP1), each carrying the DEP1 region from either 'Liaogeng5' (LG5) or 'Akitakomachi' (AKI) in the AKI and LG5 backgrounds. Our results demonstrated that AKI‐dep1/LG5‐dep1 exhibited erect panicle and enhanced grain number per panicle, thereby consequently increasing grain yield, whereas they possessed inferior grain appearance compared with AKI‐DEP1/LG5‐DEP1 in the same background. However, the effects of dep1 on grain processing quality and eating and cooking quality varied with the background. These results provide useful information for high‐yield erect panicle rice breeding by marker‐assisted selection.

Grains at different positions on rice panicles differ greatly in weight and quality, but few studies have focused on the effect of dep1 that influences panicle morphology and grain number on grain weight and quality at different spikelet positions and under different backgrounds. To clarify this, we compared spikelet characteristics and grain quality in the superior spikelets (SS) and inferior spikelets (IS), as well as sink-, source-and flow-related traits between NIL-dep1 (AKI-dep1 and LG5-dep1) and NIL-DEP1 (AKI-DEP1 and LG5-DEP1) under the Akitakomachi (AKI) and Liaogeng5 (LG5) backgrounds. The grain weight and quality in SS did not significantly differ between NIL-dep1 and NIL-DEP1 under the two backgrounds. However, the effect of dep1 on grain weight and quality in IS varied with background. AKI-dep1 significantly decreased the grain weight, processing quality, and eating and cooking quality in IS compared with AKI-DEP1, possibly due to poor grain filling and the lack of an adequate source supply and vascular system to fully meet the increased sink size. With the exception of appearance quality, the grain weight and quality of IS of LG5-dep1 were similar to LG5-DEP1, mainly due to the enlarged vascular system and similar grain filling rate and source supply. We concluded that the varied effects of dep1 on grain weight and quality under the two backgrounds could be attributed to differences in grain filling and source−sink−flow relationships.