With the continuous improvement of living standards, the preferences of consumers are shifting to rice varieties with high eating and cooking quality (ECQ). Milled rice is mainly composed of starch, protein, and oil, which constitute the physicochemical basis of rice taste quality. This review summarizes the relationship between rice ECQ and its intrinsic ingredients, and also briefly introduces the effects of nitrogen fertilizer management on rice ECQ. Rice varieties with higher AC usually have more long branches of amylopectin, which leach less when cooking, leading to higher hardness, lower stickinesss, and less panelist preference. High PC impedes starch pasting, and it may be hard for heat and moisture to enter the rice interior, ultimately resulting in worse rice eating quality. Rice with higher lipid content had a brighter luster and better eating quality, and starch lipids in rice have a greater impact on rice eating quality than non-starch lipids. The application of nitrogen fertilizer can enhance rice yield, but it also decreases the ECQ of rice. CRNF has been widely used in cereal crops such as maize, wheat, and rice as a novel, environmentally friendly, and effective fertilizer, and could increase rice quality to a certain extent compared with conventional urea. This review shows a benefit to finding more reasonable nitrogen fertilizer management that can be used to regulate the physical and chemical indicators of rice grains in production and to improve the taste quality of rice without affecting yield.

Due to climate change, flooding stress has occurred more frequently and intensively than ever before, which has become one of the major abiotic stresses affecting rice production. In tropical regions around the world, southeastern coastal countries, and southern rice production areas of China, frequent flooding disaster usually takes place during the rainy season and heavy summer rainfall, which leads to great yield losses in rice production. Currently, only a few rice genotypes are flooding-tolerant, and the relevant flooding-resistant cultivation and regulation practices are still lacking. Therefore, this review highlighted the latest studies on the physiological mechanisms of rice response to flooding stress and flooding-resistant cultivation, particularly summarizing the effect of flooding stress on rice root system architecture, plant growth, reactive oxygen metabolism, energy metabolism, radiation use efficiency, endogenous hormone metabolism, nitrogen utilization efficiency, and yield formation. In addition, the breeding strategies and cultivation regulation approaches for alleviating the flooding stress of rice were analyzed. Finally, future research directions are outlined. This review comprehensively summarizes the rice growth performance and physiological traits response to flooding stress, and sums up some useful regulation strategies, which might assist in further interpreting the mechanisms of plants’ response to flooding stress and developing stress-resistant cultivation practices for rice production.

Grain yield was greatly increased during the genetic improvement of japonica inbred rice since the 1980s in Jiangsu, east China; thus, an improved plant morphology should be expected, considering that plant morphology is a decisive factor determining grain yield. Twelve representative japonica inbred rice released from 1983 to 2013 were grown in the same fields in 2019 and 2020. Grain yield increased (p < 0.01) at 63.3 kg ha⁻¹ year⁻¹ across 2 years among rice cultivars released in different periods. The genetic improvement in grain yield was associated with increased spikelets per panicle. Single panicle weight, number of primary and secondary branches, and number of grains on primary and secondary branches were all increased with a year of release. Generally, the width of top three leaves positively correlated (while angle of top three leaves and light extinction coefficient negatively) correlated (p < 0.01) with year of release. Leaf area per tiller and leaf area index at heading and maturity, specific leaf weight, leaf photosynthetic rate, and SPAD values after heading were all increased linearly with year of release. Plant height exhibited a positive (p < 0.01) trend with year of release, as well as stem weight per tiller and K and Si concentrations of stem. Spikelets per panicle, width of top three leaves, plant height, and leaf area index, and specific leaf weight after heading positively correlated (while angle of top three leaves and light extinction coefficient negatively) correlated (p < 0.01) with grain yield and single panicle weight. Our results suggested that modern japonica inbred rice exhibited expanded sink size by spikelets per panicle, higher leaf area through leaf width, optimized leaf photosynthetic capacity, lower leaf angle and light extinction coefficient, and enhanced stem strength. These improved plant morphologies facilitated yield increases of japonica inbred rice since the 1980s in east China.

The past three decades have seen a pronounced development of conventional japonica rice from the 1990s, although little information is available on changes regarding grain yield and nutrient use efficiency during this process. Nine conventional japonica rice released during the 1990s, 2000s, and 2010s were grown under a reduced nitrogen rate, with increased planting density (RNID) and local cultivation practice (LCP) in 2017 and 2018. The rice from the 2010s had 3.6–5.5% and 7.0–10.1% higher (p < 0.05) grain yield than the 2000s and the 1990s, respectively, under RNID and LCP. The harvest index contributed more to genetic yield gain from the 1990s to the 2000s; whereas from the 2000s to 2010s, yield increase contributed through shoot biomass. Genetic improvement increased total nitrogen (N), phosphorus (P), and potassium (K) accumulation, and their use efficiencies. The rice from the 2010s showed a similar grain yield, whereas the 1990s and 2000s’ rice exhibited a lower (p < 0.05) grain yield under RNID relative to LCP. RNID increased N, P, and K use efficiencies, particularly the N use efficiency for the grain yield (NUEg) of the 2010s’ rice, compared with LCP. For three varietal types, RNID increased the panicles per m², the filled-grain percentage, and the grain weight (p < 0.05) while decreasing spikelets per panicle of the 2010s’ rice. Compared with LCP, RNID reduced non-structural carbohydrate (NSC) content and shoot biomass, at heading and maturity, while increasing the remobilization of NSC and the harvest index, especially for the 2010s’ rice. Our results suggested the impressive progressive increase in grain yield and nutrient use efficiency of conventional japonica rice since the 1990s in east China. RNID could facilitate grain yield and NUEg for modern conventional japonica rice.

It is of great interest to utilize saline fields to promote rice production in China. It has still not been established how salinity stress affects grain-filling characteristics and the relationships with yield formation of rice in a saline field. This experiment was conducted with Ningjing 7 (salinity-tolerant rice variety) and Wuyunjing 30 (salinity-susceptible rice variety) in a non-saline field and a high-saline field in 2021 and 2022. The grain yields of Ningjing 7 and Wuyunjing 30 in a high-saline field were 37.7% and 49.8% lower (p < 0.05) than in a non-saline field across two years. Ningjing 7 exhibited a higher (p < 0.05) grain yield than Wuyunjing 30 in a high-saline field. The reductions in filled-grain percentage and grain weight in inferior grains were greater than in superior grains of Ningjing 7 and Wuyunjing 30. For Ningjing 7 and Wuyunjing 30, the total starch contents in superior and inferior grains at 15, 30, and 45 days after heading were reduced (p < 0.05) in a high-saline field compared to a non-saline field. The ADP–glucose pyrophosphorylase, granule-bound starch synthase, and starch synthase activities after heading in superior and inferior grains in a high-saline field were lower (p < 0.05) than those in a non-saline field, and the reductions were more pronounced for Wuyunjing 30. The maximum grain-filling rate and mean grain-filling rate were decreased, while the time to achieve the maximum grain-filling rate was increased in a high-saline field compared to a non-saline field, especially for Wuyunjing 30. The mean grain-filling rate and grain-filling amount in superior and inferior grains during the early, middle, and late stages were lower in a high-saline field than in a non-saline field. For Ningjing 7 and Wuyunjing 30, the reductions in the grain-filling amount in the inferior grains during the early, middle, and late stages in a high-saline field were greater than those in superior grains. Our results suggest that salinity stress inhibited the grain-filling rate, reduced the total starch content and affected key enzyme activities, which led to the poor sink-filling efficiency and yield performance of rice in a saline field, especially for the salinity-susceptible variety.

Early-maturing japonica/indica hybrids (EJIH) have recently been released, performing a yield potential of 13.5 t ha⁻¹ and greater yield increase over conventional japonica rice (CJ) and hybrid indica rice (HI) in production. More spikelets per panicle and improved grain-filling efficiency underlined the basis for the superior yield performance of EJIH. However, few studies are available on the panicle traits and grain-filling characteristics of EJIH, as well as their differences to CJ and HI. In our study, two EJIH, two CJ, and two HI cultivars with similar growth patterns were grown in the same fields. EJIH had a 12.2–18.8% increased (p < 0.05) grain yield relative to CJ and HI, mainly attributed to their higher daily grain yield. Although it had a lower panicle per m², EJIH exhibited 28.0–38.3% more (p < 0.05) spikelets per m² from an increase of 58.0–87.8% (p < 0.05) in spikelets per panicle than CJ and HI. Compared with CJ and HI, EJIH had a higher single panicle weight and more grains in the six parts of the panicle, especially in the upper secondary branches (US) and middle secondary branches (MS). EJIH exhibited a higher leaf area index (LAI), leaf area duration (LAD), leaf photosynthetic rate, and SPAD values after heading, which helped increase shoot biomass weight at heading and maturity and post-heading biomass accumulation. For CJ and HI, the grain-filling dynamics of grains in the six parts were all well simulated by the Richards equation. For EJIH, the grain-filling dynamics of grains in the lower secondary branches (LS) were well fitted by the logistics equation, with the Richards equation simulating grain positioning on the other five parts. EJIH had a lower mean grain-filling rate (GR_mean) and longer days and grain filling amounts (GFA) during early, middle, and late stages than CJ and HI. Our results suggest EJIH gave a yield advantage over CJ and HI through a higher daily grain yield. The panicle traits and grain-filling characteristics differed greatly among the three cultivar types. Compared with CJ and HI, EJIH had lower GR_mean and higher days and more grains in the panicle during early, middle, and late stages, which contributed to an increased GFA after heading, improved filled-grain efficiency, and higher grain yield.