Eating Quality Of Rice Research Articles

Reduced Nitrogen Application with Dense Planting Achieves High Eating Quality and Stable Yield of Rice.

Rational nitrogen (N) application can enhance yield and improve grain eating quality in rice. However, excessive N input can deteriorate grain eating quality and aggravate environmental pollution, while reduced N application (RN) decreases rice yield. Reduced N application with dense planting (RNDP) is recommended for maintaining rice yield and improving N use efficiency. However, the effects of RNDP on the rice grain eating quality and starch structure and properties remain unclear. A two-year field experiment was conducted to investigate the effects of RNDP on the rice yield, grain eating quality, and starch structure and properties. Compared to conventional N treatment, RN decreased significantly the rice yield, while RNDP achieved a comparable grain yield. Both the RN and RNDP treatments improved significantly the rice eating quality. The high eating quality of RNDP was attributed to increased gel consistency, pasting viscosity, and stickiness after cooking as well as decreased protein content. A further analysis of starch structure and properties revealed that RNDP decreased the relative crystallinity, lamellar intensity, gelatinization enthalpy, and retrogradation enthalpy of starch. Therefore, RNDP achieved a stable rice yield and enhanced rice eating quality. These findings provide valuable insights into obtaining optimal quality and consistent yield in rice production under reduced N conditions.

Physicochemical Properties and Fine Structure of Starch in Jinong Xiangruan 1 and DGR1 Soft Rice Varieties Cultivated in Different Regions of China

Rice, a staple food for billions around the globe, is cultivated in numerous forms. Among them, soft rice is well known, which is characterized by its tender, creamy consistency and desirable texture. In this study, we examined the physicochemical properties and fine structure of starch from two soft rice varieties, Jinong Xiangruan 1 and DGR1, cultivated in different regions in China (Baodi District, Tianjin City; Liaoning Province; and Fengyang City, Anhui Province). The aim was to understand how amylopectin content (AC) influences rice quality. This research aims to bridge the knowledge gap regarding the role of amylopectin in determining rice’s adhesive consistency and viscosity. Significant regional differences were observed in yield components such as the number of grains per panicle, seed setting rates and 1000-grain weight, with Liaoning generally showing higher performance metrics compared to other regions. Physicochemical analysis highlighted that though glue consistency and taste values showed little regional variation, AC significantly influenced rice hardness and viscosity. Rapid Visco Analyzer (RVA) profile analysis further demonstrated distinct differences in viscosity characteristics, underscoring the regional impacts on starch behavior. Additionally, molecular weight distribution and amylopectin chain length analysis, conducted via SEC-MALLS-RI and ICS ion chromatography, revealed notable differences in starch composition across varieties and locations. The findings suggest that environmental conditions play a crucial role in defining starch characteristics and, consequently, the eating quality of rice. This provides valuable insights for breeding high-quality japonica rice with broad adaptability.

One-Time Mixed Nitrogen Fertilizers Application Enhances Yield and Eating Quality of Late-Maturing Medium Japonica Rice in the Yangtze River Delta

This study addresses the uncertainty regarding the potential of a one-time basal application of mixed nitrogen (N) fertilizer to optimize both yield and eating quality of late-maturing medium japonica rice Nangeng 9108 and Fenggeng 1606 in the Yangtze River Delta. Six distinct combinations of blended N fertilizers were evaluated, with conventional split fertilization serving as the control. The blended formulations combined controlled-release N fertilizer (CRNF) and quick-acting N fertilizer (CNF) at a 1:1 ratio. Furthermore, the CRNF component was a combination of two CRNF types with varied N-release durations at a 4:1 ratio, leading to treatments labeled A1, A2, B1, B2, C1, and C2. Over a 2-year study, treatments B1, B2, C1, and C2 matched or surpassed the control in grain yield, with C1 and C2 yielding 2.83–4.85% more. Among the above high-yield treatments, C1 showcased the best rice eating quality, which exhibited increased peak viscosity, hot viscosity, cool viscosity, breakdown, and taste value of milled rice, and a decrease in rice protein content (PC). This enhancement in quality correlated with N accumulation patterns and their interplay with sink capacity. Specifically, a higher N accumulation resulted in a robust sink capacity under the C1 treatment, thus reducing N availability per unit sink capacity (NAV) and rice PC, ultimately enhancing the overall palatability of milled rice. Conclusively, the C1 fertilizer blend demonstrates potential in concurrently boosting yield and eating quality of late-maturing medium japonica rice in the region.

Long-term straw return improves cooked indica rice texture by altering starch structural, physicochemical properties in South China

Straw return can improve rice eating quality by modifying starch formation from long-term field trials, whereas the relevant mechanisms are still unknown. A long-term field experiment, including straw removal (CK), straw burning return (SBR), and straw return (SR) was conducted to investigate the starch structure, physicochemical properties, and cooked rice textures of indica early- and late-rice. Compared with CK, SBR and SR enhanced relative crystallinity, amylopectin long chains in both rice seasons, and gelatinization temperatures in late rice. Compared to SBR, SR decreased protein content and amylopectin short chains but increased starch branching degree, breakdown, and stickiness, ultimately contributing to improved starch thermal and pasting properties. Meanwhile, SR decreased hardness, cohesiveness, and chewiness, resulting in cooked texture meliorated, which was mainly attributed to amylopectin chain length and starch granule size. The results suggest that SR increased cooked texture of indica rice by altering starch structural and physicochemical properties.

Effects of postponing nitrogen topdressing on starch structural properties of superior and inferior grains in hybrid indica rice cultivars with different taste values.

Nitrogen (N) fertilizer management, especially postponing N topdressing can affect rice eating quality by regulating starch quality of superior and inferior grains, but the details are unclear. This study aimed to evaluate the effects of N topdressing on starch structure and properties of superior and inferior grains in hybrid indica rice with different tastes and to clarify the relationship between starch structure, properties, and taste quality. Two hybrid indica rice varieties, namely the low-taste Fyou 498 and high-taste Shuangyou 573, were used as experimental materials. Based on 150 kg·N hm-2, three N fertilizer treatments were established: zero N (N0), local farmer practice (basal fertilizer: tillering fertilizer: panicle fertilizer=7:3:0) (N1), postponing N topdressing (basal fertilizer: tillering fertilizer: panicle fertilizer=3:1:6) (N2). The starch granules of superior grains were more complete, and the decrease in small granules content and the stability of starch crystals were a certain extent less than those of inferior grains. Compared with N1, under N2, low-taste and high-taste varieties large starch granules content were significantly reduced by 6.89%, 0.74% in superior grains and 4.26%, 2.71% in inferior grains, the (B2 + B3) chains was significantly reduced by 1.61%, 0.98% in superior grains, and 1.18%, 0.97% in inferior grains, both reduced the relative crystallinity and 1045/1022 cm-1, thereby decreasing the stability of the starch crystalline region and the orderliness of starch granules. N2 treatment reduced the ΔHgel of two varieties. These changes ultimately contributed to the enhancement of the taste values in superior and inferior grains in both varieties, especially the inferior grains. Correlation analysis showed that the average starch volume diameter (D[4,3]) and relative crystallinity were significantly positively correlated with the taste value of superior and inferior sgrains, suggesting their potential use as an evaluation index for the simultaneous enhancement of the taste value of rice with superior and inferior grains. Based on 150 kg·N hm-2, postponing N topdressing (basal fertilizer: tillering fertilizer: panicle fertilizer=3:1:6) promotes the enhancement of the overall taste value and provides theoretical information for the production of rice with high quality.

Unveiling the Impact of Different Nitrogen Fertilizer Levels on Rice’s Eating Quality through Metabolite Evaluation

We investigated the variations in metabolites associated with the quality of rice consumption when exposed to varying nitrogen fertilizer levels, as well as the regulatory role of pivotal metabolites within metabolic pathways. This research employed Hongyang 5 as the subject of experimentation, examining the metabolites of Hongyang 5 at three different nitrogen levels using non-targeted metabonomic analysis. The findings indicated that the overall assessment of the eating quality/palatability (CEQ) and amylose contents (AC) of Low nitrogen (D1: 180 kg·ha−1) was notably greater than that of Medium nitrogen (D2: 270 kg·ha−1) and High nitrogen (D3: 315 kg·ha−1). Conversely, the amylopectin (APC), total starch (SC), and protein contents (AP) of D1 were remarkably lower than those observed in D2 and D3. The starch debranching enzyme (DBE) and granule-bound starch synthetase (GBSS) of D1 were remarkably higher than those of D2 and D3. The soluble starch synthase (SSS) of D1 was the lowest. The ADP-glucose pyro-phosphorylase (AGP) and starch branching enzyme (SBE) of D3 were remarkably higher than that of D1 and D2. We identified 76 differential metabolites (DMs) between D1 and D2 (20 up-regulated and 56 down-regulated). A total of 88 DMs were identified between D3 and D1 (42 up-regulated and 46 down-regulated). A total of 57 DMs were identified between D3 and D2. Most of the DMs related to rice-eating quality were involved in the lipid metabolic pathway and amino acid metabolic pathway. The essential metabolites within the metabolic pathway are classified as lipid metabolites and are (13(S)-hydroperoxylinolenic acid, PGB2, 3-phosphocholine, 7-epijasmonic acid, 20-carboxyleukotriene B4 and 11-dehydro-thromboxane B2), amino acid metabolites (4-guanidinobutanoic acid, (3R, 5S)-1-pyrroline-3-hydroxy-5-carboxylic acid, citric acid, (S)-2-Acetolactate, L-glutamine, L-2, 4-aminobutyric acid and putrescine). These key metabolites may be affected by nitrogen fertilizer conditions and play critical regulatory roles in the metabolic pathway, resulting in differences in rice eating quality.

Impacts of Inherent Components and Nitrogen Fertilizer on Eating and Cooking Quality of Rice: A Review.

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.

Novel Grade Classification Tool with Lipidomics for Indica Rice Eating Quality Evaluation.

The eating quality evaluation of rice is raising further concerns among researchers and consumers. This research is aimed to apply lipidomics in determining the distinction between different grades of indica rice and establishing effective models for rice quality evaluation. Herein, a high-throughput ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight (UPLC-QTOF/MS) method for comprehensive lipidomics profiling of rice was developed. Then, a total of 42 significantly different lipids among 3 sensory levels were identified and quantified for indica rice. The orthogonal partial least-squares discriminant analysis (OPLS-DA) models with the two sets of differential lipids showed clear distinction among three grades of indica rice. A correlation coefficient of 0.917 was obtained between the practical and model-predicted tasting scores of indica rice. Random forest (RF) results further verified the OPLS-DA model, and the accuracy of this method for grade prediction was 90.20%. Thus, this established approach was an efficient method for the eating grade prediction of indica rice.

Screening new breeding japonica rice varieties by rice quality, three processing characteristics, and odor characteristics.

Rice's yield, cooking, and sensory quality are primary considerations in selecting new breeding rice varieties, which are determined by the rice eating quality such as processing and flavor characteristics. Thus, in this study, to advance the breed of new superior japonica rice varieties, the differences in the rice quality, processing characteristics, and flavor characteristics between 12 newly-bred varieties (H2-36, H2-42, H2-53, H2-59, H2-63, H2-73, H2-74, H2-79, H2-81, H2-82, H2-89, and H2-91) and 1 commercial variety (Kenyu38) were analyzed. The results indicated that H2-42 has a reasonable length-to-width ratio (1.51), high rice yield, good color, reasonable amylose, protein content, excellent water existence index, accessible storage, and the highest taste value. Electronic nose results showed significant differences in aldehydes, ketones, and alcohols among 13 rice varieties. Aroma analysis results showed that H2-42 had the highest n-hexanal (14.63µg/kg), (E,E)-2,4-nonadienal (37.24µg/kg), nonanal (19.93µg/kg), and decanal (4.81µg/kg); those were important aroma components in cooked rice. The Pearson correlation analysis showed that hardness, springiness, cohesiveness, trough viscosity, peak time, and pasting temperature were the crucial factors that affected rice quality. According to partial least squares regression analysis, total color change, final viscosity, setback, (E)-2-heptenal, and 2-methyl-undecanol were the most important factors that distinguished the rice quality. In conclusion, H2-42 rice was better apparent quality, processing characteristics, and aroma compounds. Therefore, H2-42 has the potential for identification and promotion. PRACTICAL APPLICATION: The results from this study will provide data support for the cultivation, application, and quality improvement of high-quality rice varieties. In addition, it gives new ideas and methods for studying rice eating quality.

Quality Characteristics of Japonica Rice in Southern and Northern China and the Effect of Environments on Its Quality

Four types of japonica rice including non-soft japonica rice from northern China planted in the northern region (NSJRNN), non-soft japonica rice from northern China planted in the southern region (NSJRNS), non-soft japonica rice from southern China planted in the southern region (NSJRSS), and soft japonica rice from southern China planted in the southern region (SJRSS) were adopted as materials to reveal the quality characteristics of japonica rice in southern and northern China and the effect of environments on its quality. Compared with NSJRNN, higher temperatures during the grain-filling stage in southern China resulted in poor processing and appearance qualities of NSJRNS and NSJRSS. Due to the increased protein content (PC), the eating qualities of NSJRNS and NSJRSS were bad. While for SJRSS, with low apparent amylose content (AAC) and few large-sized starch granules, the eating quality was better than that of NSJRNS and NSJRSS and even comparable to NSJRNN. Therefore, with a relative high PC of rice under high temperature condition in southern China, it could be one of the effective ways to reduce AAC appropriately to obtain a good eating quality of rice.

Development of SNP Markers from GWAS for Selecting Seed Coat and Aleurone Layers in Brown Rice (Oryza sativa L.).

Ninety-five percent of the general nutrients in rice are concentrated in the rice bran and germ, and many nutrients such as vitamins, minerals, dietary fiber, and essential fatty acids, as well as antioxidants such as tocopherol, are lost during milling. In this study, we investigated the thickness of seed coat and aleurone layers using a 294 rice core collection, and found candidate genes related to thickness of seed coat and aleurone layers, by performing a genome wide association study (GWAS) analysis using whole genome resequencing data. Two primer pairs that can be used as high-resolution melting (HRM) markers were developed. As a result of genotyping BC2F2 individuals derived from a cross between “Samgwang” and “Seolgaeng”, and using corresponding HRM markers, it was possible to finally develop HRM markers for selecting seed coat and aleurone layer thickness. This is expected to be used as basic data for the application of gene editing using CRISPR/Cas9 technology and for establishing a breeding strategy for high eating quality rice using molecular genetic technology.

Long-term blast control in high eating quality rice using multilines

Combining genetic heterogeneity and crop homogeneity serves a dual purpose: disease control and maintaining harvest quality. Multilines, which consist of a genetically uniform mixture of plants, have the potential to suppress disease while maintaining eating quality, yet practical methods that facilitate commercial use over large geographical areas are lacking. Here, we describe effective rice multiline management based on seed mixture composition changes informed by monitoring virulent blast races in Niigata Prefecture, Japan. The most elite nonglutinous cultivar, Koshihikari, was converted into the multiline, Koshihikari BL (blast resistant lines) and planted on 94,000 ha in 2005. The most destructive rice disease, blast, was 79.4% and 81.8% less severe in leaves and panicles, respectively, during the 2005–2019 period compared to the year 2004. In addition, fungicidal application was reduced by two-thirds after the introduction of BL. Our results suggest that seed mixture diversification and rotation of resistant BL provides long-term disease control by avoiding virulent race evolution.

Coordinating High Yield and Superior Eating Quality of Rice: A Case Study of Hybrid Varieties Derived from Longke638S and Jing4155S

The planting area of hybrid rice (Oryza sativa L.) has continuously decreased in recent years partially because of the low eating quality. Longke638S and Jing4155S are two elite male sterile lines, which are used for developing many hybrid varieties with large planting areas in China. Here, 21 hybrid rice varieties of an incomplete diallel cross population with Longke638S and Jing4155S as female parents were planted under field conditions for two consecutive years, aiming to investigate the physiological and transcriptomic characteristics that is required for coordinating high yield and superior eating quality. As a result, grain yield ranged from 7.15 to 9.23 t ha−1 in 2019 and from 7.49 to 9.23 t ha−1 in 2020, and a negative relationship was identified between yield and quality-related traits. Hybrid varieties with Longke638S as the female parent (LLY) had higher yield but lower eating quality than those with Jing4155S as the female parent (JLY). The higher yield of LLY over JLY was due to higher biomass production and N uptake as well as higher yield stability across planting years, while their lower grain quality can be mainly ascribed to lower amylose content and alkali spreading value. Male parents significantly affected yield-related traits of LLY and eating quality-related traits of JLY. Candidate genes involved in grain starch biosynthesis were differentially expressed between LLYHZ, JLYHZ, and JLY1212, such as Wx and ALK. Overall, this study examined the relationship between grain yield and eating quality and identified the physiological and molecular traits that limited grain yield or eating quality of LLY and JLY hybrid varieties.

淮北地区麦茬机插优质食味粳稻氮肥减量的精确运筹

<p id="C3">At present, “nitrogen reduction” has become one of the planting measures for good eating quality<italic> japonica</italic> rice, but the scientific management plan of nitrogen fertilizer after nitrogen reduction is unclear and further studies are needed. From 2018 to 2019, good eating quality<italic> japonica</italic> rice varieties including Nanjing 505 and Nanjing 2728 were planted as materials, and four ratios of basic and tillering to panicle fertilizer including 5:5, 6:4, 7:3, and 8:2 were arranged with nitrogen application 20% less than conventional nitrogen application (CK) for mechanical transplanting rice under wheat straw returning. Yield, rice quality, and nitrogen utilization were investigated to determine the effects under nitrogen reduction for good eating quality<italic> japonica</italic> rice. The results were as follows: With the increase of the proportion of the basic and tillering fertilizer in the total nitrogen application, the yield increased first and then decreased. The 7:3 treatment had the highest yield, reaching 11,134.80-11,280.19 kg hm ^-2 for two years. Compared with CK, the yield increased by 1.23%-2.54% and there was no significant difference. The 7:3 treatment group could obtain sufficient population spikelet, higher seed-setting rate, and 1000-grain weight. With the increase of the proportion of nitrogen application in the previous period, the dry matter weight of the population at (N-n) stage and jointing stage displayed an increasing trend, while the dry matter weight at heading stage and maturity stage, the dry matter accumulation from heading to maturity, the final nitrogen accumulation and the nitrogen efficiency increased first and then decreased, and reached a peak in the 7:3 treatment. Compared with CK, nitrogen reduction treatment could ensure higher dry matter accumulation of the population at the later stage by increasing the proportion of nitrogen fertilizer application (7:3) at the early stage, which significantly improved nitrogen absorption and nitrogen use efficiency of the population by 14.10%-15.48%, and significantly higher than CK. For eating quality of<italic> japonica</italic> rice under nitrogen reduction, the processing quality deteriorated with the increase proportion of basic and tillering nitrogen, the appearance quality became better, the cooking and eating quality improved, and rice RVA profile was optimized. Under the condition of the whole wheat straw to the field, nitrogen was reduced by 20% compared with conventional fertilization. To achieve the comprehensive planting goal of high-yield, high-quality, and high-efficiency for good eating quality rice to a certain extent, nitrogen application with the ratio of basic and tillering fertilizer to panicle fertilizer 7:3 could stabilize or slightly increase the yield of good eating quality<italic> japonica</italic> rice, greatly increase nitrogen use efficiency, and improve the appearance and taste quality in rice.

Differences in starch multi-layer structure, pasting, and rice eating quality between fresh rice and 7 years stored rice

With the continuous improvement of rice production capacity and the accumulation of reserves year by year, rice sometimes has to be stored for a long time. However, long-term storage of rice has poor sensory properties, which may be related to the structural changes of starch. Different from the previous studies on short-term storage of rice (often 3–12 months), the focus of this study was to understand the differences in starch multi-layer structure, pasting, and rice eating quality between 7 years stored rice and fresh rice. Our research indicated that 7 years stored rice showed higher hardness and lower stickiness compared to fresh rice, which ultimately led to poorer eating quality. These bad changes were related to differences in starch multi-layer structure. The 7 years stored rice had lower amylose content, a lower thickness of crystalline lamellae and short-range ordered structure of starch, and more large starch granules. In particular, the volume mean diameter of 7 years starch was more than 4 times that of fresh starch. 7 years stored rice had more large granular starch and unstable crystal structure, which led to the increase of pasting temperature and the decrease of gelatinization enthalpy during starch gelatinization, and ultimately reduced the eating quality of the rice.

Earlier Heading Induced by Chemical Mutation of High Eating Quality Rice Variety, “Ichihomare”

Earlier Heading Induced by Chemical Mutation of High Eating Quality Rice Variety, “Ichihomare”

Genetic Control and High Temperature Effects on Starch Biosynthesis and Grain Quality in Rice.

Grain quality is one of the key targets to be improved for rice breeders and covers cooking, eating, nutritional, appearance, milling, and sensory properties. Cooking and eating quality are mostly of concern to consumers and mainly determined by starch structure and composition. Although many starch synthesis enzymes have been identified and starch synthesis system has been established for a long time, novel functions of some starch synthesis genes have continually been found, and many important regulatory factors for seed development and grain quality control have recently been identified. Here, we summarize the progress in this field as comprehensively as possible and hopefully reveal some underlying molecular mechanisms controlling eating quality in rice. The regulatory network of amylose content (AC) determination is emphasized, as AC is the most important index for rice eating quality (REQ). Moreover, the regulatory mechanism of REQ, especially AC influenced by high temperature which is concerned as a most harmful environmental factor during grain filling is highlighted in this review.

Balance rice yield and eating quality by changing the traditional nitrogen management for sustainable production in China

Total yield of rice in China has been greatly improved in recent decades. However, this yield improvement is excessively dependent on the input of nitrogen (N) fertilizer. In recent years, since the demand for rice quantity has basically been met, consumers pay more attention to rice quality, especially the eating quality. Increasing N application improves the yield of rice, but it changes the protein and amylose content in rice, generally reducing the eating quality. It is necessary to establish a more reasonable N management to balance yield and eating quality for rice sustainable development in China. In this study, we assessed the effectiveness of various N managements on rice yield and eating quality by meta-analysis. Under traditional N management, increasing the amount of total N and late-stage N applications weaken the yield increase and decrease the eating quality with the significant increase in protein and amylose content in rice. By reducing total N and late-stage N application input, eating quality and N use efficiency could be significantly improved. Further, conditional inference tree analysis indicated that adjusting the amount of late-stage N application was a major measure to improve traditional N fertilization, since it could increase agronomic N use efficiency in rice production and balance yield maintenance and eating quality improvement. Our supplementary experiment results further confirmed that adjusting N management could improve the rice yield and eating quality with less N input. Thus, we propose the following adjusting N management strategies for rice sustainable production in China: (1) Decreasing the traditional high N rate is absolutely necessary, although it will slightly decrease rice yield, but significantly improve rice eating quality and N use efficiency; (2) Reducing the amount of late-stage N application appropriately could improve the rice eating quality; (3) Improving agronomic N use efficiency is the key to balance rice yield and eating quality. Our results provide an important reference for the future N management in rice production for the purpose of achieving high yield and better eating quality.

Comparative metabolomics analysis reveals the variations of eating quality among three high-quality rice cultivars

Good eating quality is a highly desirable trait of rice which determines its commercial value and market share. However, the molecular basis of this trait remains largely unknown. Here, three high-quality conventional rice cultivars, including two superior eating quality cultivars Meixiangzhan-2 (MXZ) and Xiangyaxiangzhan (XYXZ), and one ordinary eating quality cultivar Huanghuazhan (HHZ), were analyzed by comparative metabolomics to identify the inherent mechanism for the formation of superior eating quality. The results showed 58.8% of common differential substances between MXZ vs HHZ and XYXZ vs HHZ were enriched in MXZ and XYXZ, whereas 39.2% of them were prominently decreased compared with HHZ, mainly including amino acids, carbohydrates, lipids, phenolamides, and flavonoids, which may be the primary factors leading to the differences of taste and flavor among these three cultivars. We also found that lysine derivatives and fatty acids may have a close relationship with taste. These results above provide important insights into the taste-forming mechanism of rice and will be beneficial for superior eating quality rice breeding.

The Influence of Nitrogen Application Level on Eating Quality of the Two Indica-Japonica Hybrid Rice Cultivars.

Indica-japonica hybrid rice cultivars show great yield potential but poor eating quality and require more nitrogen (N) input relative to japonica rice. However, the effect of N levels on the eating quality of indica-japonica hybrid rice is little known. A field experiment was carried out to investigate the effects of four N levels on two indica-japonica hybrid rice cultivars (Yongyou12 and Yongyou17) differing in eating quality. The results showed that the contents of amylose chains and water-insoluble storage proteins, especially prolamin, increased largely under a high N level, leading to deterioration of the rice-eating quality, although a low N level (100 N kg/ha) had a less negative effect on the eating quality. Moreover, both of the indica-japonica hybrids had high ratios of inferior grains (IG), and the ratio of IG increased with the N level. Grain weight and the immature ratio of IG were reduced and increased with the N level, respectively, which are also factors for deterioration of the eating quality. The two cultivars differed greatly in the responses of eating quality to the N level, with Yongyou17 being more sensitive than Yongyou12. The current results indicated that a high N level deteriorates the eating quality of indica-japonica hybrid rice mainly due to a large increase of IG.