Search Results (1,409)

Rice yield is a complex polygenic trait influenced by intricate interactions among component characters. In this study, integrative quantitative genetics and multivariate models were used to dissect yield architecture and trait networks, and identify the promising genotypes among 21 rice genotypes that were tested in a randomized block design with three replicates. Analysis of variance revealed highly significant genotypic differences (p < 0.001) for most agronomic, yield, and grain-quality traits. Genetic variability analysis revealed high genotypic and phenotypic coefficients of variation, together with high heritability and genetic advance, for grain density per panicle, number of grains per panicle, biomass, flag leaf area, tillering ability, harvest index, and grain yield, indicating considerable genetic potential for genetic improvement. Pearson’s correlation and path coefficient analyses revealed that biomass and number of grains per panicle were the major determinants of grain yield per hill, with biomass exhibiting the strongest positive association (r = 0.678) and the largest direct effect. Principal component analysis indicated that the first two principal components explained 51.4% of the total phenotypic variation, with yield components, biomass, tillering traits, and grain-quality attributes contributing most strongly to genotype differentiation. Hierarchical cluster analysis grouped the genotypes into four distinct clusters, revealing substantial phenotypic divergence and valuable parental combinations for hybridization. The multi-trait selection index identified VAR16 as the most promising genotype, followed by VAR1, VAR17, VAR18, and VAR12, owing to their desirable combination of high grain yield and superior grain quality. Overall, this study offers a robust foundation for ideotype breeding and parental selection to enhance rice productivity and grain quality under subtropical conditions. Full article

The brown planthopper (BPH, Nilaparvata lugens) is a major insect pest of rice (Oryza sativa L.) causing severe yield losses across Asia. Although the resistance gene OsBph32 from the cultivar Ptb33 enhances BPH resistance, its molecular and physiological mechanisms remain unclear. Here, we investigated its function using OsBph32-overexpressing lines combined with physiological, transcriptomic, and metabolomic analyses. Overexpression of OsBph32 in the susceptible cultivar 9311 significantly increased resistance to BPH, as indicated by reduced plant damage and suppressed insect growth. This was associated with increased reactive oxygen species accumulation and callose deposition, suggesting activation of early defense responses. Multi-omics analyses revealed that OsBph32 is associated with transcriptional changes in genes involved in cell wall biosynthesis, phenylpropanoid metabolism, and carbon metabolism. Metabolomic profiling further showed increased accumulation of flavonoids, phenolamides, and lignin-related metabolites under BPH infestation, together with changes in carbon metabolism and starch accumulation. Collectively, these results suggest that OsBph32 is associated with coordinated changes in structural reinforcement, secondary metabolism, and carbon metabolism during insect attack, which may contribute to enhanced rice resistance and provide new insights into non-NLR-mediated insect defense mechanisms in plants. Full article

Rice (Oryza sativa L.) is one of the world’s major staple foods. However, its production is severely constrained by rice blast disease, caused by Magnaporthe oryzae, which leads to substantial yield losses. Conventional management relies on fungicides and chemical treatments; however, these methods raise concerns regarding the development of pathogen resistance and potential environmental impacts. This study evaluated carrageenan from Hypnea musciformis, collected from the coast of Saint Martin (92°19′21.28″ E and 20°37′38.12″ N), located in the Bay of Bengal, Bangladesh, as a natural plant growth promoter as well as a biocontrol agent. Carrageenan was characterized by high sulfate (19–35%) and galactose (12–18%) contents, with FT-IR confirming characteristic κ-carrageenan functional groups. Application of 15% carrageenan significantly increased the germination of seed (27%), seedling vigor (93%), shoot and root lengths (54% and 47%), and biomass compared with untreated controls. Carrageenan markedly suppressed M. oryzae, inhibiting mycelial growth (83%), reducing conidiogenesis and conidial germination, and decreasing lesion length in detached leaves and potted plants. Treated rice seedlings exhibited improved soluble sugars, photosynthetic pigments, proline, phenolic and flavonoid contents, and enhanced antioxidant enzyme activities such as CAT (catalase) and POD (peroxidase), while lowering oxidative stress markers such as H₂O₂ and MDA (malondialdehyde). These results demonstrate that carrageenan from H. musciformis enhances rice growth and elicits defense responses against rice blast, offering a sustainable and environmentally friendly alternative to chemical-based fungicides for integrated M. oryzae management. Full article

Fusarium oxysporum-associated disease symptoms in rice (Oryza sativa L.) seedlings represent an experimentally tractable model for evaluating microbiome-mediated disease suppression under controlled conditions. Biological control of Fusarium-associated disease development in rice provides a promising ecological alternative to chemical fungicides. However, the mechanisms underlying the spatial reconfiguration of the host plant multicompartment microbiome in response to complex inoculants remain insufficiently understood. In this study, we investigated the ability of the monoculture Bacillus amyloliquefaciens Bn1 (B. amyloliquefaciens Bn) and phototrophic–heterotrophic consortia composed of Nostoc sp. J-1 and B. amyloliquefaciens Bn1 to suppress Fusarium oxysporum infection, with parallel profiling of bacterial and fungal communities in rhizosphere soil, the root endosphere, and the phyllosphere using 16S rRNA and ITS amplicon sequencing. Phenotypic screening showed that microbial inoculant application significantly reduced the disease index by up to 55% while maintaining plant dry weight. The protective phenotype was not primarily associated with shifts in alpha diversity, but rather with compartment-specific reorganization of microbial communities. These findings suggest that biological control efficacy was associated less with the overall taxonomic scale of microbiome disturbance than with the formation of a functionally balanced, compartment-specific holobiont architecture but by the formation of a functionally balanced, compartment-specific holobiont architecture, providing a conceptual basis for the targeted design of next-generation phototrophic–heterotrophic biopreparations. Full article

Rice (Oryza sativa L.) production is constantly threatened by devastating diseases such as rice blast, bacterial blight, and brown planthopper infestation. The AP2-type transcription factor OsHTR (also known as SMOS1/SHB/RAL1/NGR5/GR5) has been previously implicated in hormonal signaling networks and nitrogen use efficiency; however, its role in disease resistance remains largely unexplored. In this study, we functionally characterized OsHTR in disease resistance using knockout (KO) and overexpression (OE) transgenic lines in the ZH11 background. Transcriptome analysis revealed that differentially expressed genes in the htr mutant were significantly enriched in plant–pathogen interaction pathways, with multiple NBS-LRR and NB-ARC resistance-related genes upregulated. Real-time PCR validation confirmed the upregulation of 15 candidate resistance genes in the htr mutant. Comprehensive resistance evaluations suggested that HTR-KO lines exhibited enhanced resistance to rice blast and bacterial blight compared to wild-type ZH11 and HTR-OE lines, which displayed moderate susceptibility. In contrast, all lines remained highly susceptible to brown planthopper, indicating a disease-specific regulatory function of OsHTR. Furthermore, targeted knockout of individual upregulated resistance-related genes (LOC_Os10g04090, LOC_Os12g29690, LOC_Os02g11980, and LOC_Os11g11770) and OsHTR-interacting gene LOC_Os06g03710 confirmed their distinct contributions to blast and bacterial blight resistance but did not establish them as direct targets of OsHTR. Collectively, our results indicate that OsHTR functions as a negative regulator of disease resistance in rice, likely acting through transcriptional repression of defense-related genes, although direct binding remains to be demonstrated. This study uncovers a novel regulatory module connecting AP2-type transcription factors to disease resistance and provides valuable genetic resources for molecular breeding of broad-spectrum-resistant rice cultivars. Full article

Biomass-derived carbon dots (CDs) have attracted increasing attention in agriculture due to their simple synthesis and low environmental impact. In this study, CDs were synthesized from guava (Psidium guajava) leaves using a hydrothermal method (200 °C, 15 h). The particles had an average size of 6.17 nm and a quantum yield of 2.46%, confirming the successful synthesis of fluorescent carbon nanomaterials from the natural precursor. The effects of CDs on rice (Oryza sativa L., variety HT1) were evaluated through both seed treatment and field application. Soaking seeds in a 200 ppm CD solution for 24 h significantly enhanced shoot and root lengths (28.87 mm and 34.00 mm, respectively) among the tested treatments. In field trials, applying CDs at the same concentration also promoted plant growth, as evidenced by improvements in plant height, leaf development, tillering, and flag leaf characteristics. These changes were reflected in yield, with the highest grain yield of 6.13 t ha⁻¹ at 200 ppm, exceeding that of the control treatment. The observed positive effects may be due to enhanced photosynthetic activity and better control of oxidative processes in plants. Nevertheless, the effect was less pronounced at higher concentrations. This trend suggests a dose-dependent response. Full article

The quality of rice grain impacts milling yield, market acceptance, and product value. Physical quality is determined by many traits, such as chalkiness, whiteness, vitreous whiteness, caryopsis length, and width. Breeding for these traits is challenging due to their quantitative nature, environmental effects, and time and labor requirements to evaluate these traits. The digital grain analyzer (S21) equipment determines rice grain physical quality by image-based analysis; however, its use remains restricted. Thus, here we aimed to evaluate S21 efficiency to determine the physical quality of rice grains and estimate the genetic diversity of the trait using a Brazilian panel of 152 irrigated rice genotypes as a working model. We accessed total whiteness, vitreous whiteness, chalkiness degree, chalky grain rate, white belly, grain length, width, and length/width ratio. Our results demonstrated that S21 allowed the characterization of the genotypes according to physical traits, facilitating grouping and separation of accessions and correlation analyses between quality traits. It was also possible to estimate the heritability of quality traits. S21 was efficient in characterizing the physical quality of rice grains and determining their genetic diversity. The equipment is an effective tool exhibiting potential application by breeder programs. Full article

The present study was conducted to study the effect of exposure time to ultraviolet-C (UV-C) radiation on seed germination, fungal suppression and seedling growth of three Egyptian rice cultivars, namely, Sakha 105, Sakha 108, and Giza 183. Experiments were carried out under controlled laboratory conditions. Rice seeds were exposed to UV-C radiation with a wavelength of 253.7 nm and intensity of 1960 µW cm² for 0 (control), 10, 20, 30, 40, 50, and 60 min. Initial seed health testing showed the presence of several seed-borne fungi, mainly Alternaria alternata, Rhizoctonia solani, and Fusarium verticillioides, in addition to Aspergillus niger and Aspergillus flavus. Results revealed that UV-C exposure time, rice cultivar and their interactions significantly (p < 0.05) affected germination percentage, reduction percentage of seed fungal infection, and seedling growth parameters. The optimum exposure time was 30 min, which was found to maximize germination and improve shoot and root growth to achieve high levels of fungal suppression. Giza 183 exhibited the highest average germination percentage (92.40%), while Sakha 105 obtained the highest shoot height (17.00 cm) and root length (12.91 cm). The results indicate that UV-C irradiation is an effective, residue-free and environmentally sustainable seed treatment technology for improving rice seed quality as well as early seedling performance. Full article

The translocation of sucrose into spike grains during the grain-filling stage directly affects rice yield and quality. The sugar transporters OsSWEET11 and OsSWEET15 are key sucrose transporters essential for rice (Oryza sativa L.) grain filling. To elucidate their effects on grain traits, we analyzed sequence polymorphisms of these two genes in 139 landrace rice varieties from Yunnan, China, and conducted association and haplotype analyses. Our results indicated that grain filling degree was closely associated with grain shape, where wider grains negatively impacted grain plumpness. The association analysis revealed eight significant SNPs: six located in the coding region of OsSWEET15 that influenced grain length, thickness, density, and 1000-grain weight (TGW), while two SNPs in OsSWEET11 affected TGW and the thickness of milled rice grains. Haplotype analysis further validated these trait associations: OsSWEET15 Hap2 and Hap3 conferred longer grains (with Hap2 additionally increasing TGW and Hap3 enhancing grain density/plumpness), whereas Hap1 produced narrower and thicker grains. Consistently, OsSWEET11 Hap2 was also linked to higher TGW. The superior haplotypes identified here deepen our understanding of the genetic basis of rice grain filling and serve as potential molecular markers for marker-assisted rice breeding. Full article

The canopy closure stage is a critical phase of rice (Oryza sativa L.) development that influences canopy structure and final grain yield. Accurate and continuous monitoring of canopy closure dynamics is therefore essential for variety screening and cultivation optimization. This study combines unmanned aerial vehicle (UAV) remote sensing technology with deep learning-based semantic segmentation to establish an efficient framework for quantifying rice canopy closure dynamics. UAV RGB images were acquired for 198 hybrid rice varieties during early growth stages and used to build a canopy segmentation dataset. Three semantic segmentation models, i.e., DeepLabv3+, U-Net, and PSPNet, were systematically evaluated. Results show that DeepLabv3+ performed the best and enabled precise extraction of rice canopy features, obtaining a mean intersection over union (mIoU) of 0.86. Based on the extracted canopy coverage, the Gompertz model was utilized to characterize temporal canopy closure trajectories for all varieties, achieving an average R² of 0.978. Subsequently, five key dynamic indicators were derived, including canopy closure limit value (K), initial growth coefficient (a), growth rate coefficient (b), maximum instantaneous growth rate (MGR), and days to maximum growth rate (Tm). K-means clustering analysis was performed on these indicators to categorize all rice varieties into three clusters, disclosing pronounced differences in early-stage canopy development characteristics. Correlation analysis further demonstrated that canopy closure dynamics were closely associated with grain yield. Overall, while acknowledging the limitations of a single-season and single-site dataset, this study provides a scalable and objective framework for quantifying rice canopy closure dynamics, offering valuable support for variety selection, cultivation optimization, and high-yield rice production. Full article

Anthocyanins are important flavonoid compounds with significant antioxidant activity and ornamental value in rice. In this study, using upland rice landrace 17SM-19 as the material, the anthocyanin content in leaves was determined at the one-(S1) and two-leaf stages (S2). The anthocyanin content at S1 (43.37 U/g) was significantly higher than that at S2 (16.54 U/g). With S1 considered the control, a total of 9865 differentially expressed genes (DEGs) were identified in the S2, among which 4702 were upregulated and 5163 were downregulated. Functional enrichment analyses revealed that these DEGs were significantly enriched in terms and pathways such as photosynthesis and ribosome. Screening of these DEGs identified 10 structural genes and four regulatory genes associated with anthocyanin biosynthesis. Quantitative real-time PCR verified the reliability of the transcriptome data. These results provide valuable clues for revealing the molecular mechanism underlying anthocyanin biosynthesis in rice leaves. Full article

Optimizing rice (Oryza sativa L.) plant architectype is an important approach to coordinating the source–sink relationship and unlocking yield potential. In this study, using the large-panicle rolled-leaf variety ST-12 and the small-panicle flat-leaf variety Nipponbare, we systematically compared plant architectype traits, photosynthetic characteristics, biomass accumulation, carbohydrate accumulation and remobilization, source–sink characteristics, and yield under two nitrogen levels in field conditions to test the hypothesis that excessive leaf rolling influences the accumulation and translocation of photosynthetic products and disrupts the source–sink balance. The results showed that Nipponbare exhibited significantly higher yield than ST-12 under both nitrogen levels, attributable to its higher number of productive panicles, grain-filling percentage, and thousand-grain weight. Although ST-12 had a higher single-leaf photosynthetic rate and leaf area index, its top three leaves were excessively rolled, reducing its canopy light interception and canopy photosynthetic rate, thereby leading to significantly lower stem NSC content at heading and biomass accumulation during grain filling compared with Nipponbare. Notably, ST-12 had higher contents of cellulose, hemicellulose, and lignin in the stem at heading, directing more pre-anthesis photosynthetic products into structural carbon, while the translocation of non-structural carbohydrates to grains was not affected. Further analysis revealed that ST-12 had a lower source capacity, sugar–spikelet ratio, source–spikelet ratio, and source–sink ratio than Nipponbare, whereas its total spikelet number and sink capacity were significantly higher. Correlation analysis showed that source characteristic indices and the source–sink ratio were positively correlated with yield, grain-filling percentage, and thousand-grain weight, while sink characteristic indices were negatively correlated with these traits. In conclusion, excessive leaf rolling impairs canopy photosynthesis, leading to a large sink but weak source imbalance. For large-panicle varieties, a higher source–sink ratio, not simply larger sink size or total biomass, is the key to high yield. Full article

High temperature during flowering and grain filling severely reduces rice yield and grain quality. Split potassium (K) fertilization can mitigate such heat-induced damage, yet its mechanisms linking grain filling, endogenous hormones and grain performance remain unclear. Here, a two-year pot experiment was conducted to explore the effects of split K application on rice yield, quality and hormonal metabolism under high temperature. Four treatments included ambient temperature with full basal K (AT-K₁₀₀), high temperature with full basal K (HT-K₁₀₀), and two split K regimes under high temperature (HT-K₇₀₊₃₀, HT-K₃₀₊₇₀). Split K application decreased abscisic acid (ABA) levels at 5 days after anthesis (DAA), increased indole-3-acetic acid (IAA), zeatin riboside (ZR) and gibberellin A3 (GA₃) at 5 DAA, and maintained higher IAA and GA₃ levels until 20 DAA. The ratios of ABA/IAA and ABA/GA₃ were also reduced at both 5 and 20 DAA. These hormonal alterations optimized grain-filling dynamics, prolonged active filling duration and improved middle- and late-stage filling rates, thereby promoting grain weight accumulation and suppressing chalkiness formation. Compared with HT-K₁₀₀, HT-K₇₀₊₃₀ increased yield by 8.75%, which was attributed to improved seed-setting rate and 1000-grain weight. HT-K₃₀₊₇₀ enhanced spikelet number per panicle, seed-setting rate and 1000-grain weight, but significantly decreased effective panicles, resulting in no obvious yield advantage. Furthermore, split K application effectively reduced grain chalkiness, with a more pronounced effect at a higher panicle-stage K proportion. Under ongoing global warming, K management can be tailored to production goals: higher basal K is preferable for yield pursuit, while increasing panicle K topdressing effectively improves grain quality. Full article

Nitrogen (N) and potassium (K) co-management is critical for optimizing grain yield in rice. However, the interactive effects of N supply and K application timing on cultivars with contrasting N efficiencies remain poorly understood. Here, we conducted a two-year field experiment (2020 and 2021) using two japonica rice cultivars, Shennong 265 (SN265) and Meifengdao 61 (MFD61), under three N rates (180, 225, and 270 kg ha⁻¹) and three K application ratios (basal: panicle = 3:7, 5:5, and 7:3). SN265 exhibited a 20.31% higher average grain yield than MFD61, primarily attributable to increased crop growth rates during the tillering–booting (14.08%) and grain-filling–maturity phases (31.88%). Under moderate N supply (N₁₈₀ and N₂₂₅), increasing the proportion of basal K application (K_7:3) consistently improved dry matter accumulation, enzyme activity, and grain yield in both cultivars. However, under high-N conditions (N₂₇₀), excessive early-season K application reduced grain yield in MFD61 by 7.69%. For SN265, further yield improvement required an enhanced net assimilation rate during the tillering–booting phase. Although this study was conducted at a single site with only two cultivars, it provides a physiological and agronomic framework for cultivar-specific N–K co-management strategies to improve grain yield and nutrient use efficiency. Full article

Nanotechnology has attracted increasing attention in agricultural and environmental research, but the biological effects and potential risks of nanoparticles based on non-essential elements remain insufficiently understood. This study investigated the physiological and biochemical responses of rice (Oryza sativa L.) seedlings to yttrium oxide nanoparticles (Y₂O₃ NPs) and zirconium oxide nanoparticles (ZrO₂ NPs) at 5, 25, and 100 mg/L under hydroponic conditions. The results showed that neither Y₂O₃ nor ZrO₂ NPs significantly affected visible growth traits or SPAD-based leaf chlorophyll status, suggesting that seedling morphology and leaf greenness remained relatively stable during exposure. However, both nanoparticles induced distinct biochemical responses. Y₂O₃ NPs caused root-level stress-like responses, including increased malondialdehyde (MDA) accumulation and suppressed peroxidase (POD) and catalase (CAT) activities under specific exposure conditions. In contrast, ZrO₂ NPs were more closely associated with the activation of antioxidant defenses, particularly through enhanced POD activity and increased root CAT activity. Inductively coupled plasma mass spectrometry (ICP-MS) analysis further showed that Y and Zr were mainly retained in roots, with root Y reaching 5014.12–11,255.05 mg kg⁻¹ dry weight (DW) under Y₂O₃ NP exposure and root Zr reaching 189.68 mg kg⁻¹ DW under high-concentration ZrO₂ NP exposure. Bio-transmission electron microscopy (bio-TEM) supported the root-dominant localization of nanoparticle-associated electron-dense aggregates. These findings indicate that Y₂O₃ and ZrO₂ NPs exert material-specific effects on rice seedlings, with root accumulation and antioxidant regulation serving as more sensitive indicators than visible growth traits. However, further research is needed to clarify the long-term environmental fate of Y₂O₃ and ZrO₂ NPs and to assess their potential ecological and food safety risks in agricultural systems. Full article