Forage-grain ratoon rice (FG-RR) is a sustainable system designed to enhance ratoon rice yield and quality while simultaneously producing high-quality whole-plant rice forage through early harvesting of the immature main crop (MC) for silage. This study examined the effects of planting density and mowing time on forage and grain productivity and quality, to optimize ecological and economic benefits. Field experiments were conducted using two cultivars, Liangyou 6326 and Taoyouxiangzhan, across five planting densities (17.26 & times; 104-34.52 & times; 104 hills ha-1) and four mowing stages (heading, milk-ripening, dry-ripening, and full maturity). Forage and ratoon crop (RC) yields, quality traits, resource utilization efficiency, and economic returns were assessed. Increasing planting density initially promoted but subsequently reduced both forage and RC yields. Delayed mowing increased forage yield but, after an initial rise, reduced RC yield. The optimal combination-mowing at the milk-ripening stage with a planting density of 28.82 & times; 104 hills ha-1 produced forage containing 53.72% neutral detergent fiber, 21.26% starch, and 9.93% crude protein, meeting standards for high-quality silage. In the RC season, the head rice rate reached up to 58.61% with a chalkiness level as low as 4.17%, meeting high-quality edible rice standards. TOPSIS analysis and economic evaluation indicated that this management strategy yielded the highest overall performance, generating 3086.08 USD & centerdot;ha-1. Integrating this optimal mowing time with optimal density produced 31.88 t & centerdot;ha-1 of high-quality forage and 7.13 t & centerdot;ha-1 of premium-grade rice. This integrated strategy enhances resource utilization efficiency, grain quality, and profitability, offering a practical approach for the sustainable development of FG-RR systems.

The leaf area index (LAI) is a key parameter for characterizing crop growth and water use efficiency. Therefore, efficient and accurate monitoring of LAI is essential for precision rice management. To overcome the limitations of traditional LAI measurement methods, which are time consuming, labor intensive, and difficult to scale, this study proposes an inversion framework that integrates multi-source UAV remote sensing features with machine learning models. The framework incorporates color indices (CIs) derived from RGB imagery, vegetation indices (VIs) derived from multispectral data, texture features (TIs), and texture feature indices (TFIs), and employs six machine learning algorithms to develop optimized LAI estimation models for the rice booting stage. The results indicate that at a flight altitude of 30 m, the CNN model integrating CIs and TIs achieved an accuracy of R2 = 0.815. At 60 m, the RF model combining VIs and TFIs showed superior performance, with an R2 of 0.866. Further integration of CIs, VIs, and TFIs at 30 m produced the best results, increasing R2 to 0.901, reducing RMSE to 0.273, and raising RPD to above 3.0. These findings demonstrate that TFIs significantly enhance the spectral-spatial representation capability of multispectral data, thereby improving model accuracy. The combined use of CIs and VIs across different sensors compensates for the inherent limitations between spectral and spatial information, while the integration of multi-resolution TIs and TFIs effectively overcomes the constraints of single-source data. Overall, the proposed approach provides a robust and efficient solution for high-precision LAI estimation during critical growth stages of rice, offering strong support for precision agricultural management.

The forage-grain ratoon rice system enables the harvesting of main crop for silage, followed by the harvesting of the ratoon crop for grain. A two-year study was conducted in Xinyang City, Henan Province, China to assess the effects of nitrogen (N) application rates (135, 270, and 405 kg ha-1 ) and stubble heights (0, 15, 25, 35, and 45 cm) at the main crop harvest on forage quality and ratoon performance in the forage-grain ratoon rice system. Results showed that high stubble heights (35 and 45 cm) significantly improved forage quality via reduced neutral/acid detergent fiber and increased crude protein and starch contents compared with the stubble height of 0 cm. High stubble heights also shortened the ratoon growth period by 12-18 d and increased the daily mean temperature and solar radiation by up to 1.93 degrees C and 0.49 MJ m-2 d-1 , respectively. When combined with 270 or 405 kg N ha-1 , high stubble heights increased tiller density, leaf area index, and canopy light interception, thereby enhancing post-anthesis biomass accumulation, crop growth rate, and the use efficiencies of both thermal energy and solar radiation in the ratoon crop. Consequently, the ratoon grain yield was increased by 43%-60%, which was mainly due to more panicles from the upper two nodes. These findings suggest that optimizing the stubble heights and N management is key to maximizing agronomic performance in the forage-grain ratoon rice system.

Rapeseed (Brassica napus L.) is a globally important oilseed crop that provides edible oil, protein meal, and feedstock for biodiesel production. However, seedling establishment is highly sensitive to water-availability extremes, limiting yield stability in industrial oilseed production. Seed pelleting is a practical technology for improving germination uniformity and stress resilience, but its mechanisms under contrasting water-availability conditions remain insufficiently understood. Here, we integrated physiological, hormonal, enzymatic, transcriptomic, and metabolomic analyses to compare pelleted and unpelleted rapeseed seeds under high- and low-water-availability conditions simulated using 3 and 36 g L⁻¹ agar media, respectively. Under low-water-availability conditions, pelleting promoted gradual water absorption, reaching 75% after 24 h, and was associated with higher headspace CO₂ concentration, GA₄ accumulation (18 ng g⁻¹ FW), and maintained activities of glycolytic and tricarboxylic-acid-cycle enzymes. These responses were accompanied by superior final germination (95.8%) and a higher vigor index (5.9). In contrast, under high-water-availability conditions, pelleting increased ABA and JA concentrations to 90 and 2.8 ng g⁻¹ FW, respectively, reduced the activities of carbohydrate-metabolic enzymes, and activated redox- and lipid-remodeling networks, resulting in lower seed vigor. Overall, pelleting differentially modulated hydration, hormonal signaling, and metabolic responses according to water availability. These findings provide a mechanistic basis for developing and field-testing climate-smart, water-responsive pelleting technologies for industrial oilseed rape, including hydrophilic, water-retentive formulations for low-water-availability seedbeds and oxygen-releasing or gas-permeable formulations for excess-water-prone conditions.

Background Late embryogenesis abundant (LEA) proteins are pivotal for seed development and abiotic stress responses in plants. Tartary Buckwheat (Fagopyrum tataricum), a highly adaptable and nutritionally rich pseudocereal, has garnered significant recent interest due to its exceptional stress resistance. Despite its genome sequencing completion, a comprehensive analysis of the LEA gene family in Tartary Buckwheat remains uncharacterized. Results This study employed bioinformatics approaches for a genome-wide identification of the LEA gene family (designated FtLEA genes) in F. tataricum. We analyzed its subfamily composition, evolutionary relationships, and spatiotemporal expression patterns. A total of 53 FtLEA genes were identified, distributed randomly across eight chromosomes, and categorized into eight subfamilies. Intraspecific collinearity analysis revealed 11 pairs of collinear genes, with no tandem duplications observed. Phylogenetic analysis indicated that FtLEA genes exhibit homology with sequences from both dicotyledonous and monocotyledonous model plants. Interspecies collinearity analysis further demonstrated numerous collinear gene pairs between FtLEA genes and those in both diploid and polyploid dicot crops. Promoter cis-element analysis unveiled various hormone- and abiotic stress-responsive cis-elements within the FtLEA subfamily genes. Spatiotemporal expression profiling demonstrated that FtLEA genes are specifically expressed in seeds and roots, and show significant responses to abiotic stress and hormone treatments, suggesting crucial roles during seed development and stress adaptation. Conclusion Our comprehensive genomic analysis identified 53 FtLEA genes in Tartary Buckwheat. Selection screening indicated that 11 pairs of intraspecific collinear FtLEA genes underwent strong purifying selection, implying functional conservation during evolution. The predominant expression of FtLEA genes in seeds and roots suggests their involvement in sensing and regulating abiotic stress. This study establishes a foundational understanding of the evolutionary relationships and potential biological functions of FtLEA genes, providing a basis for further targeted research.

Multiscale structures of starch and their interactions with proteins are key factors in determining taste qualities of rice. This study explored six high-quality rice cultivars to uncover the factors contributing to superior eating quality. It was revealed that high-quality rice featured large starch granules, and size distributions were positively correlated with breakdown viscosity but negatively correlated with cool paste viscosity. The proportion of fb2 chains (DP 25-36) in amylopectin was positively correlated with peak viscosity and negatively correlated with cohesiveness of cooked rice. Conversely, the proportion of fb3 chains (DP ≥ 37) was negatively correlated with hot paste viscosity. Gelatinization temperatures had negative correlation with fa chains (DP 6-12), while positive correlation with fb1 chains (DP 13-24). Fourier transform infrared spectroscopy and Raman spectroscopy revealed that the enhanced hydrogen bonding interactions within starch-protein complexes strengthened gels and resulted in higher peak viscosities. These findings provide new perspectives for breeding high-quality rice cultivars.

Higher grain weight and stronger seed dormancy are key objectives for improving rice (Oryza sativa) yield and inhibiting pre-harvest sprouting. Therefore, identifying genes that coordinately regulate grain weight and seed dormancy is an urgent priority. Here, we report that knocking out miR1866 (KO1866) increased grain weight and reinforced dormancy. We identified the transcript of ubiquitin-specific processing protease 7 (OsUBP7), which encodes a protein with deubiquitination activity in vitro, as the primary target of miR1866. Consistent with miRNA-directed repression, OsUBP7 transcript abundance generally showed a spatiotemporal pattern opposite to miR1866 accumulation during rice development. Overexpression of native OsUBP7 (UBP7-OE) or a miR1866-resistant form (mUBP7-OE) phenocopied KO1866 by producing heavier grains with stronger dormancy. The miR1866-OsUBP7 module also altered the expression of genes associated with sucrose and starch metabolism, cell-cycle control, grain development, and abscisic acid (ABA) biosynthesis and signaling. Accordingly, KO1866, UBP7-OE, and mUBP7-OE plants contained more ABA and responded more sensitively to exogenous ABA than wild type. OsUBP7 interacted with OsDA1 (encoded by Os06g0182500) and UBIQUITIN-CONJUGATING ENZYME (OsUCE1; encoded by Os02g0833300), thereby affecting hull cell division and ABA signaling and ultimately regulating grain weight and seed dormancy, respectively. Our results indicate that the miR1866-OsUBP7 module regulates grain weight and seed dormancy in rice, highlighting its potential for engineering crops with improved yields and stronger seed dormancy.

The L-type amino acid transporter (LAT) family facilitates the cellular transport of amino acids and polyamines. However, the functions of LAT transporters in rice remain insufficiently characterized. In this study, we identified a significant negative association between OsLAT1 transcript levels and tiller number in rice. Transcriptional analysis revealed that OsLAT1 is predominantly expressed in leaves, basal tissues, and panicles. Subcellular localization assays showed that the OsLAT1 protein is localized to the endoplasmic reticulum and is strongly induced by Asp), Leu, spermidine (Spd), and spermine (Spm). Furthermore, under hydroponic conditions, moderate concentrations of arginine (Arg) and serine (Ser) partially promoted bud outgrowth and biomass in OsLAT1-overexpressing plants, whereas these effects diminished at higher Arg/Ser concentrations. In contrast, OsLAT1 facilitated the transport of spermidine (Spd) and spermine (Spm), thereby promoting axillary bud elongation and rice growth. These findings provide insights into amino acid transporter-mediated regulation of rice plant architecture and offer potential targets for yield improvement.

Understanding the mechanisms underlying yield differences among rice planting regions is crucial for boosting the yield potential of low-producing regions and ensuring global food security. Although climate factors affecting rice yields in different sites have been widely studied, the microbial ecological processes and environmental mechanisms that promote super rice yields remain poorly understood. This study analyzed the composition, assembly mechanisms, and functions profiles of rhizosphere and soil microbial communities in five representative super rice production regions across China, including Handan (Hebei, temperate zone, drab soil), Xinyang (Henan, subtropical zone, clay loam soil), Xupu and Longhui (Hunan, subtropical zone, paddy soils), and Gejiu (Yunnan, tropical highland paddy soil). Our results revealed that the assembly mechanisms of rhizosphere microbial communities were primarily dominated by stochastic processes (accounting for 79.54 %), mainly including dispersal limitation and undominated processes. In contrast, bulk soil microbial communities were predominantly shaped by deterministic processes (contributing to 72.18 %), primarily homogeneous selection. Distance-decay relationships indicated that bulk soil microbial communities were more susceptible to latitude and environmental factors (R-2 = 0.13, p < 0.001), while rhizosphere microbial communities exhibited greater stability due to the buffered rhizosphere microenvironment. Partial Least Squares Path Modeling further demonstrated that rhizosphere microbes exerted stronger influences on rice growth compared with bulk soil microbes. Further predictions showed that the high-yielding Gejiu site selectively recruited rhizosphere microbes enriched in nutrient cycling and transport pathways, including glyoxylate and dicarboxylate metabolism, inositol phosphate metabolism, and nitrogen metabolism. These functions enhanced nutrient availability and supported higher biomass (70.96 g plant(-1)). Collectively, our findings suggest that the stochastic assembly of rhizosphere microbial communities confers functional stability, and their enrichment in nutrient cycling functions represents a key biological mechanism driving regional differences in super rice yields.

The starch molecular structure is crucial for rice noodle manufacturing, however, the intrinsic mechanism by which starch molecular structure regulates the gel properties and quality of rice noodles remains unclear. Here, the regulatory mechanisms were investigated using six rice cultivars with apparent amylose content (AAC) of 19.84%-25.82%. Results revealed that the rice with high AAC was associated with superior sensory scores and uniform moisture distributions in noodles. AAC was positively correlated with water absorption rate, hardness, and chewing index, while negatively correlated with optimum cooking time and broken strip rate. The fa chains (DP 6-12) of amylopectin showed a negative correlation with water absorption rate, while fb1 chains (DP 13-24) showed the opposite correlation. Additionally, fb3 chains (DP 37-100) were negatively related to hardness. Short-chain amylose (100 ≤ X < 1000) was negatively correlated with adhesiveness and positively correlated with chewing index. For 1000 ≤ X < 2000, there was a negative correlation with hardness, chewing index, and sensory score, while being positively correlated with broken strip rate and adhesiveness. The 2000 ≤ X < 20,000 was positively correlated with adhesiveness and negatively correlated with chewing index. Amylose content and chain length distributions regulated gel formation and noodle quality by controlling the cold paste viscosity, setback viscosity, crystalline structure, and gelatinization temperature. Rice cultivars with higher proportions of fb1 and short-chain amylose of 100 ≤ X < 1000 performed better in noodle production, contributing to higher hardness, chewing index, water absorption rate, while exhibiting lower adhesiveness and broken strip rate. These findings elucidated the connections between molecular structure of starch, supramolecular structure of gels, and macro qualities of noodles, providing new perspectives for selection and breeding of rice cultivars suitable for noodle production.

Kam Sweet Rice (KSR), a distinctive group of glutinous rice landraces, has evolved over millennia through agro-ecological adaptation by the Dong ethnic group in the 'He' cultivation zone of Southeast Guizhou, China. This study examined the genetic diversity of 388 glutinous rice landraces from the region, comprising 325 KSR and 63 non-KSR varieties, using Simple Sequence Repeat (SSR) sequencing. Results revealed that non-KSR germplasm exhibited significantly higher genetic diversity than KSR germplasm. Collectively, diversity patterns were strongly shaped by the numerical predominance of genetically similar KSR germplasms, resulting in an uneven distribution of genetic diversity between KSR and non-KSR groups. Five strategies were applied to construct and evaluate core collections (see Methods for full details). Among them, the simulated annealing algorithm (SA)-based Allelic Richness Maximization Strategy (SANA) (20% sampling intensity) demonstrated superior performance in preserving genetic diversity, except for the number of alleles (Na) and observed heterozygosity (Ho), where the Modified Heuristic Sampling (M-HS) strategy (13.66% sampling intensity) performed better at lower sampling intensities. By optimizing both approaches, a core collection of 65 germplasms was established, capturing 90.86% of alleles and retaining key genetic parameters. This core set effectively represents the genetic diversity of the entire collection, providing a strong foundation for future germplasm innovation and utilization.

Low temperature stress seriously restricts the seedling establishment and yield stability of direct-seeded rice. In this study, we proposed sodium nitroprusside (SNP), a nitric oxide donor, as a functional component for seed pelleting to improve the low temperature resistance of rice. SNP pelleting treatment significantly increased seed germination, vigour and seedling growth at low temperature. Physiological mechanism analysis showed that SNP enhanced the antioxidant system (key enzyme activity and non-enzymatic antioxidant content), reduced the oxidative damage index, increased α-amylase activity and soluble sugar and protein contents, and promoted energy supply. Hormone detection found that SNP treatment increased gibberellin and reduced abscisic acid levels, which was beneficial to germination. In summary, SNP pelleting can synergistically enhance the low temperature adaptability of rice through multiple pathways and provide an effective technical approach for stable yield of direct seeded rice under low temperature stress.

Nitrogen (N) is an essential macronutrient for food crops. Plants respond to low N (LN) stress through altering their root morphology. Strigolactones (SLs) are important modulators of root growth in plants. However, the functions of SLs and their downstream pathway in N-modulated formation of crown roots (CRs) remain unclear. In this study, we found that LN inhibits the occurrence of CRs in rice, with significant differences observed between japonica and indica varieties. A natural variant of D17, a gene involved in SL biosynthesis, was identified as participating in this process, revealing that SL is involved in LN-inhibited CR development in rice. Mutations in D17 and D53 (an SL signalling repressor) caused CR development under N deficiency. Under LN conditions, the perception of SLs by D14 triggered the ubiquitin-proteasome-mediated degradation of D53, thereby releasing SPL14 and SPL17 (SPL14/17) to inhibit CR formation and ultimately resulting in fewer CRs in rice. Additionally, SPL14/17 interacted with WOX11 and repressed its transcriptional activity by attenuating its DNA-binding ability. Moreover, loss of WOX11 function in the spl14 spl17 double mutant suppressed the enhanced CR formation observed under LN conditions, demonstrating that WOX11 acts downstream of SPL14/17 to induce rice CR formation in response to different levels of N supply. Taken together, our findings suggest a novel regulatory pathway in which D53-SPL14/17-WOX11 module modulates CR development adaptations to changes in N availability in rice.

Nitrogen (N) management is critical for ensuring food security and mitigating greenhouse gas (GHG) emissions. In rice paddies, the effectiveness of N management in maximizing yields and minimizing N losses is highly dependent on local environmental conditions and thus varies widely across regions. However, the influence of optimized, site-specific N management on methane (CH4) emissions remains poorly quantified and is not reflected in current IPCC Tier 1 methodologies. Here, we synthesize data from multiregional field experiments and conduct a meta-analysis to show that locally optimized N management practices-such as delayed fertilizer application, reduced N input, and deep placement-reduce CH4 emissions from rice paddies by 16%-21%. The experiments further show that these practices suppress CH4 emissions by lowering soil N availability and organic matter decomposition, thereby limiting substrates for methanogenesis. Combining survey data from 155 counties with machine learning models, we estimate that implementing optimized N strategies across China's rice-growing regions could reduce CH4 emissions by 16% while simultaneously increasing rice yields by 7%. These findings underscore the dual benefits of locally optimized N management for agricultural productivity and climate change mitigation, and provide a foundation for improving CH4 emission estimates under diverse management regimes.

The mechanisms underlying quality formation of forage-grain ratoon rice (FG-RR) were investigated using transcriptomics and metabolomics. Results revealed that mowing at milky-ripe stage (MS) significantly enhanced the percentages of brown rice, milled rice, and head rice compared to full-ripe stage (FRS), with increases of 2.37%, 2.40%, and 13.19%, respectively. Additionally, it had lower amylose and protein contents than FRS, decreasing by 8.09% and 26.28%. From heading stage to FRS, peak viscosity, fb3 (DP ≥ 37) chain of amylopectin decreased, whereas gelatinization temperatures and fb1 (DP 13-24) chain first increased and then decreased. Transcription levels of granule-bound starch synthase, starch branching enzymes, and starch isoamylase elevated during wax-ripe stage and FRS, resulting in the increased amylose content and altered amylopectin structure. Enhanced glycolysis, amino acid synthesis, and storage protein biosynthesis pathways contributed to increased protein content. MS mowing was more favourable for texture of cooked FG-RR, which provided a foundation for cultivating high-quality rice.

Nitrogen (N) fertilizers increase rice yield but it may also reduce rice quality, and the underlying mechanism is not elucidated. Here the impacts of different N levels on starch synthesis of two super hybrid indica rice cultivars were investigated. The apparent amylose content (AAC) showed a reduction of 15.70%-18.95% in response to N application from 0 to 400 kg N ha-1, while protein content increased by 35.73%-46.56%. More protein accumulation in endosperm at 400 kg N ha-1, affecting starch development and resulting in a higher proportion of fa (DP 6-12) chain and reduced fb2 (DP 13-24) and fb3 (DP ≥ 37) chains. Metabolomics and transcriptomics analyses indicated that under 200 kg N ha-1 treatment, transcription levels of starch synthase and starch branching enzymes were increased compared to 0 and 400 kg N ha-1, leading to an increase in AAC and changes in amylopectin chain length distribution. Nitrogen fertilizer increased the activity of nitrate reductase, glutamine synthetase (GS), and glutamate synthetase (GOGAT), promoting the GS/GOGAT cycle. Enhancement of nitrogen metabolism affected starch synthesis metabolism. The appropriate application of N fertilizer regulated the balance between carbon and nitrogen metabolism, improving processing and cooking qualities of super hybrid rice.

Ratoon rice is vital for enhancing global rice production, largely depending on high-stubble management to secure yield. However, this key practice leads to significant heterogeneity in grain quality among panicles regenerated from different stem nodes, typically distinguished as the second (D2), third (D3), and lower nodes (D4) from the top. This study investigated four rice cultivars to examine differences in grain quality, cooked rice texture, and starch structure among these three nodal positions. Results showed a progressive decline in quality from D2 to D4. Relative to D2, head rice rate decreased by 0.77% at D3 and 5.76% at D4, while chalkiness degree increased by 11.56% and 39.61%, respectively. Composition analysis revealed concomitant increases in apparent amylose and protein contents at D3 and D4. Starch from lower-node panicles, especially D4, exhibited smaller granules, lower crystallinity, higher proportion of short-chain amylopectin (DP 6-12), and smaller molecular size due to retarded endosperm development. These changes resulted in lower swelling power, reduced gelatinization temperature, and higher retrogradation tendency, ultimately leading to harder and less springy cooked rice. Declines in grain quality and starch structure and properties were attributed to lower temperature and reduced light intensity caused by delayed heading in lower-node panicles. Our findings provide valuable data and act as a resource for future efforts directed towards the improvement of quality in ratoon rice production.

Protein phosphatase 2C (PP2C), a member of the largest family of phosphatases in plants, plays a crucial role in regulating stress response, growth and development, and hormone signaling. The pea (Pisum sativum) is globally cultivated legume crop of significant for both food and forage. In agricultural production, abiotic stresses such as drought, soil salinity, and extreme temperature severely limit pea yield. Although the PP2C gene family is known to be critically involved in growth regulation and abiotic stress response, no systematic studies on this gene family in peas have been reported to date. In this study, 93 pea PP2C genes were identified on a genome-wide level and designated PsPP2C1 through PsPP2C93 according to their chromosomal locations. The 93 PsPP2C proteins were analyzed for parameters including amino acid sequence length, molecular weight, isoelectric point, predicted subcellular localization, exon number, and hydrophilicity. The pea PP2C gene family was divided into 13 subfamilies (A–L) and four tandem duplication and 23 segmental duplication events were identified. The expression levels of 20 selected PsPP2C genes were investigated under four types of abiotic stress and across different seed development stages. PsPP2C15 exhibited strong upregulation under all four stress conditions, with expression increasing more than 13-fold under cold stress. In contrast, expression of PsPP2C1 and PsPP2C58 was suppressed across all stress treatments. During seed development, PsPP2C7 showed notably high expression, while PsPP2C15 was highly expressed in 21-day-old leaves. Subcellular localization predictions indicated that PsPP2C15 is likely chloroplast-localized. Promoter analysis revealed an enrichment of cis-acting elements associated with photosynthesis and hormone regulation, suggesting that PsPP2C15 may play an important role in both developmental processes and abiotic stress responses in pea. This study presents the first genome-wide identification and characterization of the PP2C gene family in pea, comprising 93 members. The expression patterns of 20 PsPP2C genes were analyzed by quantitative real-time PCR (qRT-PCR), under abiotic stresses and during seed development, providing insights into their potential biological functions. Those findings suggest that the PP2C family is important for pea growth and development, with PsPP2C15 emerging as a key candidate for further investigation in abiotic stress tolerance and seed development.

The application of nitrogen (N) fertilizer increases rice yield while potentially leading to a decline in quality, but the intrinsic mechanism remains unclear. Herein, the effects of varying N levels (0, 200, 260 and 400 kg N ha-1) on the texture, rheological characteristics and starch molecular structure of four super hybrid indica rice cultivars with different yield potentials were investigated. When N levels increased from 0 to 400 kg N ha-1, the apparent amylose content (ACC) decreased by 10.68 % - 27.38 %, while protein contents increased by 10.11 % - 43.98 %. The mechanical strength of the grains weakened, but the hardness of the cooked rice increased. Furthermore, pasting viscosity decreased, whereas the storage modulus (G') increased. Appropriate N level at 200 kg N ha-1 reduced the proportion of fa (DP 6-12) chains while elevated fb2 (DP13-24) and fb3 (DP ≥ 37) chains, resulting in more ordered structures and higher gelatinization temperature. Conversely, high N at 400 kg N ha-1 led to an accumulation of protein particles in the endosperm, hindering starch granule development, which increased short chains and reduced rice quality. The response of starch molecular structures to N levels varied among the four super hybrid rice cultivars, although the overall trend remained consistent.

Rice paddies are a major, persistent source of atmospheric methane (CH4), emission rates depend on the partitioning of photosynthate carbon between the rice plant and the rhizosphere microbiome. Although ratoon season rice (RR) is shown to emit far less CH4 than main-crop rice (MC), the mechanisms have remained unresolved. This work conducts a 2-year field experiment in which RR is compared with MC and with late rice (LR) synchronized to the RR heading stage. Relative to MC and LR, RR lowers daily CH4 flux by 91%, raises daily grain yield by 34%-57%, and increases net economic return by 90%-136%. Mechanistically, 13C-labelling reveals that RR diverted more newly fixed carbon to the grain and less to the rhizosphere, thereby restricting acetate availability for methanogens. Rhizosphere metagenomics show reduced abundance of Methanobacteriaceae and down-regulation of methanogenic genes in RR. This carbon-reallocation pattern is underpinned by an abscisic acid (ABA)-mediated interaction between OsCIPK2 and OsSWEET1A, which simultaneously curtailed carbon efflux from roots and enhanced grain filling. This study is the first to establish a comprehensive framework of "ABA regulation-carbon allocation-microbial function-emission reduction and efficiency enhancement." It provides targetable strategies for carbon allocation and microbial management within climate-smart rice farming systems.