Stable growth in grain production plays a vital role in safeguarding China's food security. Given the continued decline in arable land area and the slow increase in yield per unit area, spring maize-late rice rotation system has emerged as an effective strategy to increase annual productivity through increasing cropping frequency. As a representative paddy-upland rotation system, the maize-rice system demonstrates superior annual energy-equivalent yield compared to other rice-based systems, with the late rice season exhibiting higher yield than the single-cropping late rice system. This work reviewed the current production status of the spring maize-late rice rotation and systematically analyzed its agronomic advantages, including its impacts on soil physicochemical properties, yield stability, resource use efficiency, and greenhouse gas emission patterns. Furthermore, we discuss potential approaches for improving productivity and achieving sustainable development in this rotation system. These findings provide theoretical support for optimizing high-yield cultivation techniques and promoting the large-scale adoption of this cropping pattern.

The rhizosheath is a sheath-like complex formed through the adhesion of root exudates and root hairs, especially in the root hair zone, to surrounding soil particles, microorganisms, and organic matter. It serves to protect root tips, enrich and activate rhizosphere nutrients, and enhance plant nutrient uptake. Its formation is influenced by both biological factors (e.g., rhizosphere microorganisms) and abiotic factors (e.g., soil texture, moisture, and nutrient status). In rice production, the rhizosheath holds potential for improving nutrient absorption and use efficiency, enhancing stress adaptation, and optimizing the rhizosphere microenvironment. Therefore, in-depth research on the formation mechanism of the rice rhizosheath and its intrinsic links with nutrient acquisition, environmental responses, and yield formation is of great significance for elucidating its functional role in rice growth and for promoting innovations in genetic improvement and cultivation management.

【Objective】This study aims to investigate the function of the OsLRP1 gene (Os01g72490) in rice lateral root development by phenotypic characterization and expression analysis of the lrp1 mutant.【Method】The lrp1 mutant was first identified through PCR amplification and sequencing. Bioinformatics methods were then employed to analyze the protein structure, conserved domains, transmembrane domains, and signal peptides of OsLRP1. Multiple sequence alignment and phylogenetic tree construction were conducted to explore the evolutionary relationship between OsLRP1 and LRP1 proteins from other species. Quantitative real-time PCR (qRT-PCR) was used to detect the expression levels of OsLRP1 in different rice tissues. Confocal laser scanning microscopy was utilized to observe the subcellular localization of the OsLRP1 protein. Finally, an auxin treatment experiment was performed to determine whether the regulation of lateral root development by OsLRP1 is mediated by auxin.【Result】Phenotypic analysis revealed that compared with the wild-type Zhonghua 11, the lrp1 mutant exhibited a 32% reduction in lateral root primordia number and a 21% decrease in lateral root number. At the maturity stage, the panicle length and 100-grain weight of lrp1 were reduced by 12.5% and 7.4%, respectively, compared with the wild-type. Bioinformatics analysis showed that the OsLRP1 gene belongs to the SHI transcription factor family, encoding a protein of 340 amino acids. Conserved domain analysis indicated that it is a member of the DUF (Domain of Unknown Function) family. No signal peptide or transmembrane domain was detected in the OsLRP1 protein. Subcellular localization in tobacco demonstrated that the OsLRP1 protein is localized in the nucleus. qRT-PCR results indicated that OsLRP1 is expressed in roots, stems, and leaves, with the highest expression level in leaves. Two auxin response elements (AuxREs) were identified within the 1-kb promoter region upstream of OsLRP1. The auxin treatment experiment confirmed that lateral root development in the lrp1 mutant is affected by auxin.【Conclusion】In summary, OsLRP1 regulates lateral root development in rice in an auxin signaling dependent manner and is involved in rice growth, development, and stress responses, further elucidating its crucial role in rice lateral root development.

【Objective】Low-temperature stress poses a significant threat to rice production, and the development of cold-tolerant varieties through the identification of cold resistance-related genes represents a critical strategy to address this challenge. Meta-QTL analysis offers a powerful approach to integrate quantitative trait loci governing complex agronomic traits, such as cold tolerance, across diverse genetic backgrounds. By improving the precision and reliability of candidate gene localization, this method provides a robust foundation for the cloning and breeding application of cold tolerance genes in rice. 【Methods】We conducted a comprehensive meta-analysis of 353 quantitative trait loci (QTLs) associated with cold tolerance at the seedling stage, derived from 38 independent studies. These QTLs were integrated using BioMercator 4.2, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to identify candidate genes within the Meta-QTL regions. 【Results】A total of 82 Meta-QTLs were identified, of which 67 (81.71%) had confidence intervals of less than 1 Mb. These regions encompassed 9282 annotated genes, including 25 previously reported genes associated with cold tolerance at the seedling stage. GO analysis revealed 99, 230, and 119 genes associated with abiotic stress response, environmental stress response, and transcription factors, respectively. KEGG enrichment analysis further identified 27, 69, and 9 significantly enriched genes related to abiotic stress response, stress response, and transcription factors, respectively. 【Conclusion】Through the integration and analysis of 353 QTLs related to cold tolerance at the seedling stage, 82 Meta-QTLs were identified. GO analysis pinpointed 448 candidate genes, while KEGG analysis further refined this list to 105 differentially enriched candidate genes. These findings provide valuable insights for molecular marker-assisted breeding and gene cloning for cold tolerance at the rice seedling stage.

【Objective】Leaf is the most important photosynthetic organ in rice. Screening and identification of rice leaf color mutants are beneficial for exploring the molecular regulatory mechanisms of chloroplast development and photosynthesis. 【Method】A green-revertible yellow leaf mutant 818-6-8 was obtained from the gene-editing lines of Jingeng 818. Phenotypic identification, genetic analysis, gene mapping, and transcriptome analysis for 818-6-8 were performed. 【Results】Compared with the wild type, the mutant showed an obvious yellow-leaf phenotype until the three-leaf stage, accompanied by a significant decrease in chlorophyll content. As it grew, the mutant turned green and gradually became indistinguishable from the wild type at the four-leaf stage. Fewer chloroplasts, abnormal thylakoid morphology and stromal lamellas structure were observed in the mutant. The yellow-leaf trait of 818-6-8 was controlled by a pair of recessive nuclear alleles. The target mutation site was located within a 2.29 Mb interval on chromosome 5, and 20 annotated candidate genes were listed. The expression levels of 2090 genes in the mutant were significantly changed compared to the wild type, of which 1343 genes were up-regulated and 747 genes were down-regulated. Further, the differentially expressed genes were enriched in biological processes such as chloroplast organization and cellular components such as chloroplasts. The expression of genes associated with chlorophyll biosynthesis and chloroplast development of 818-6-8 changed significantly. 【Conclusion】These results support the next studies for cloning target genes and analyzing chloroplast-development molecular mechanisms, and provide a germplasm resource for ornamental rice breeding.

【Objective】Tiller angle is an important component of rice plant type, which directly affects rice planting density and ultimately influences rice yield. Exploring and studying new QTLs/genes that regulate rice tiller angle and applying them to plant type improvement is one of the effective ways to improve rice yield. 【Method】The recombinant inbred lines (RILs) derived from the crossing and selfing of the Indian japonica rice variety M494 and indica rice variety Zhong 9B were used as experimental materials. They were planted at Fuyang and Lingshui experimental bases of China National Rice Research Institute in Zhejiang and Hainan Province from 2021 to 2023. QTL mapping and analysis of rice tiller angle were conducted based on the high-density Bin map constructed by resequencing method. 【Result】A total of nine QTLs were detected in three years, distributed on chromosomes 1, 3, 9, 11 and 12. The phenotypic variation explained by each QTL ranged from 2.54% to 57.00%, and the additive effects were all derived from the large tiller angle parent M494. Among them, the major QTL qTA9-1 for tiller angle was located in the range of 20.71−20.80 Mb on chromosome 9, with a physical map interval of 86.36 kb region. Moreover, it was repeatedly detected in 2021 and 2022, and the highest contribution rate could reach 57.00%. This region overlapped with the cloned tiller angle gene TAC1. The RT-PCR results showed that the expression level of TAC1 in the large tiller angle genotype line M109 was significantly higher than that in the small tiller angle genotype line M67. Further sequencing analysis revealed that compared with the qta9-1 genotype line M67, the qTA9-1 genotype line M109 had a C to T mutation at the 3' splice site of intron 4 of the reported TAC1, which is the TAC1 functional SNP, and we speculate that qTA9-1 is TAC1. In 2021 and 2022, a novel QTL controlling tiller angle was repeatedly detected in the 15.20−16.00 Mb interval of chromosome 3, which exhibited epistatic interaction with the major tiller angle QTL qTA9-1. A minor QTL locus regulating tillering angle was repeatedly detected in the 21.10−22.02 Mb interval of chromosome 12. 【Conclusion】 Nine QTLs for tiller angle were detected using the RIL population constructed by crossing M494 with Zhong 9B combining with the high-density genetic map, including the cloned gene TAC1, and a novel QTL for tiller angle was detected on chromosome 3. The above results provide a theoretical basis and genetic resources for further fine mapping of rice tiller angle genes and genetic improvement of plant type of rice varieties.

【Objective】Soil salinization is an important abiotic factor affecting agricultural production in China, and the identification of salt tolerance-related genes/QTLs in rice is crucial for ensuring stable rice production in saline-alkali soils. 【Method】Aigela and Xudao 10, which exhibit significant differences in salt tolerance related traits, were used as parent plants to create a doubled haploid (DH) population. Salt tolerance was identified under field and hydroponic conditions. Genotyping of the targeted population was performed using the rice 1 K mGPS SNP chip. Phenotypic data combined with genotype data of DH population were used for QTL mapping with the QTL IciMapping 4.2 software. 【Result】Through QTL mapping analysis, a total of 22 salt tolerance related QTLs were detected, including 10 QTLs for grain yield per plant, 4 for grains per panicle, 2 for root length, and 6 for root dry weight. These QTLs are located on chromosomes 1, 6, 8, 10, 11, and 12, explaining phenotypic variation of 3.37%−15.52% with LOD values ranging from 4.04 to 9.65. Based on the gene annotation, Arabidopsis homologous gene comparison, spatiotemporal expression analysis and sequence comparison within the mapping interval of qST11, a candidate gene (LOC_Os11g30560) encoding a hydroxysteroid dehydrogenase (OsHSD1) was identified. 【Conclusion】Among the 22 QTLs detected in this study, 11 were known genes or loci related to salt tolerance, and the remaining 11 were newly identified. Meanwhile, the candidate gene analysis was conducted on the newly identified salt tolerance QTL (qST11), laying a foundation for cloning of salt-tolerance related genes and deciphering their genetic regulatory networks.

【Objective】 Given the challenges of water scarcity and abundant light resources in the arid northwest region, this study aims to investigate the relationship between farmland soil moisture and crop photosynthesis to improve comprehensive resource utilization. The goal is to establish a complementary soil moisture–light mechanism, thereby promoting sustainable resource utilization.【Method】 From 2019 to 2021, field experiments were conducted at three typical experimental sites in the Yellow River irrigation area of Ningxia Hui Autonomous Region. Using traditional full irrigation as the control, different drip irrigation treatments with varying water levels were established to analyze the effects of different degrees of water stress on photosynthesis, key growth indicators, and yield components during critical growth stages of rice.【Results】 Water stress reduced the photosynthetic rate and the transpiration rate of rice and negatively affected yield components, but improved water use efficiency. The maximum net photosynthetic rate occurred at the booting stage, during which that under water stress treatments decreased significantly by 4.5%–26.6% compared to CK. The minimum value appeared at the milk-ripe stage, with a significant decrease of 4.2%–46.9% under water stress compared to CK. The maximum transpiration rate was observed at the booting stage, decreasing by 2.2%–16.8% under water stress relative to CK. The minimum transpiration rate occurred at the seedling stage, decreasing by 7.5%–40.7% under water stress compared to CK. Under water stress, rice plant height, straw height, straw dry weight, filled grain rate, 1000-grain weight, and yield decreased by 2.2%–24.3%, 0.3%–12.6%, 0.8%–11.6%, 0.5%–7.9%, 0.3%–9.2%, and 2.3%–71.5%, respectively, compared to CK. However, water consumption decreased by 33%–46%. Under mild stress, water use efficiency at the yield level increased by 1.9%–21.5% compared to CK, while leaf-level water use efficiency decreased by 2.1%–6.8%. These results indicate that mild water stress can reduce water consumption while maintaining relatively high yield, thereby improving water resource utilization efficiency. Using the TOPSIS model combined with the information weight method and entropy weight method to evaluate different water stress treatments, it was found that maintaining the soil moisture lower limit at 90%–100% of field capacity can optimize yield, quality, and water use efficiency.【Conclusion】 In arid and semi-arid regions, precisely regulated deficit irrigation strategies should be further promoted to maximize the drought resistance potential of rice. As an effective approach for water-saving agriculture, this can reduce water consumption while maintaining stable grain production.

【Objective】This study aims to investigate the effects of foliar nitrogen fertilizer (FNF) application at different times within the same period after mechanical harvesting of the main crop on the physiological characteristics, yield, and quality of ratoon rice, providing a scientific basis for increasing yield and improving quality of ratoon rice. 【Method】After the mechanical harvesting of the main crop, a field split-plot two-factor experiment was conducted in high-fertility (HF) and low-fertility (LF) fields. The main plots were assigned to rolling and non-rolling conditions, while the subplots were assigned to different FNF application times: spraying clean water on the day of harvesting (CK), and spraying FNF at 1 day (D1), 3 days (D3), and 7 days (D7) after harvesting. The physiological characteristics, yield, and quality of ratoon rice were measured to elucidate the effects of foliar nitrogen application timing on yield and quality. 【Result】The results showed that FNF significantly increased the SPAD value, dry matter weight, leaf area index, and effective panicle number of ratoon rice. Under both HF and LF conditions, FNF increased yield by 25.6%–82.8% by improving the effective panicle number. In the non-rolling area, no significant differences were observed among different FNF application timings, but all treatments significantly increased effective panicle number by 16.7%–30.6% and yield by 25.6%–36.7% compared to CK. In the rolling area, the yield enhancement effect gradually decreased with delayed FNF application. Under the D1 treatment, the effective panicle number significantly increased by 61.5% and 62.5%, and yield significantly increased by 74.9% and 82.8% under the two fertility conditions, respectively. FNF primarily improved the quality of ratoon rice by increasing the head rice rate and reducing the chalkiness rate. Compared to CK, in the non-rolling area, FNF significantly increased the head rice rate by 9.5%–17.8% and significantly reduced the chalkiness rate by 8.1%–15.3%; in the rolling area, FNF significantly increased the head rice rate by 15.0%–17.9% and significantly reduced the chalkiness rate by 9.2%–15.7%. 【Conclusion】Foliar nitrogen fertilizer application after mechanical harvesting of the main crop effectively increases the yield and quality of ratoon rice. In rolling areas, the application timing significantly affects outcomes, with the best results achieved when spraying on the day of harvesting. In non-rolling areas, the application timing has no significant effect, and FNF can be applied within 7 days after harvesting.

【Objective】To determine the effects of efficient, reduced-input pesticide and nitrogen (N) fertilizer application via unmanned aerial vehicles (UAVs) on the yield formation and energy efficiency of machine-transplanted rice. This study proposes an optimal model for adapting reduced N fertilizer and pesticide inputs to UAV operational efficiency, providing a theoretical foundation and practical basis for integrated UAV fertilizer and pesticide application systems. 【Methods】A randomized block design was used with two drone flight speeds and four fertilizer-pesticide reduction treatments. Two drone speeds were set: 5.0 m/s (F1) and 5.5 m/s (F2). Four treatments with proportionally reduced N fertilizer and pesticide application were established: conventional application rate (N1), 10% reduction (N2), 20% reduction (N3), and 30% reduction (N4). Manual conventional application (CK1) and no application (CK2) served as controls. The study examined the effects of UAV flight speed and combined reduction treatments on machine-transplanted rice yield, plant population quality, and energy efficiency, while exploring the relationship between yield formation and energy efficiency under the UAV-based integrated fertilizer and pesticide application model. 【Results】Compared with the CK1 treatment, the F1N1, F2N1, F1N2, and F2N2 treatments increased yields by 1.22%-1.96%, with no significant yield differences among treatments and disease control efficacy exceeding 84% in all cases. Notably, under 10% reduced fertilizer and pesticide application, treatments F1N2 and F2N2 exhibited increases of 1.73%-13.24% in both dry matter transport volume and rate, as well as N transport volume and rate. N partial factor productivity, N uptake efficiency, and N harvest index increased by 12.48%-12.89%, 17.84%-18.75%, and 1.86%-2.30%, respectively. Energy output, net energy and energy utilisation efficiency increased by 0.54%-0.66%, 0.98%-1.11%, and 5.47%-5.52%, respectively. Under identical fertilizer-pesticide regimes, a 10% increase in drone flight speed raised electricity consumption by 5.19%-10.11%. However, reduced labor hours offset electricity costs, yielding the highest net profit of 8,848.94 yuan/hm2 under the F2N2 treatment. This demonstrates that a 10% increase in UAV speed combined with a 10% reduction in N fertilizer and pesticide application (F2N2 treatment) enhances operational efficiency and reduces production costs (labor) while maintaining net profit. This achieves cost savings and efficiency gains, representing the optimal production model for N fertilizer and pesticide reduction adapted to UAV operational efficiency in this trial. 【Conclusion】The 10% drone speed increase coupled with 10% integrated N fertiliser and pesticide reduction drives synergistic optimization of yield, ecology, and energy efficiency in machine-transplanted rice through an optimised compensation mechanism. This achieves unified synergies of fertilizer and pesticide savings alongside high yields and efficiency, providing theoretical and technical support for fully mechanised green rice production.

【Objective】To address the problem in single-planetary-wheelset transplanter mechanisms where the seedling picking and placing motions cannot be simultaneously optimized—thereby degrading transplanting quality—we propose a segmented variable gear-ratio wheelset mechanism whose rotation direction is opposite to that of conventional transplanting mechanisms and whose input and output periods are unequal. 【Method】First, we derived the continuous meshing angular condition equation for a segmented incomplete-gear set and solved for the motion parameters required for the segmented incomplete gear set to achieve continuous meshing. Next, by combining the non-uniform transmission ratio of an oval (non-circular) gear with the cubic high-amplitude fluctuation transmission ratio of the segmented incomplete gear, we obtained the multi-step unequal-amplitude transmission ratios required for the ring-loop (ankle-shaped) seedling-transplanting trajectory. We then established a kinematic model of a non-circular gear planetary wheelset transplanting mechanism that includes incomplete gear sets and developed a MATLAB-based auxiliary design program for the transplanter. At the same time, in accordance with rice seedling transplanting agronomic requirements and using a human–machine interactive selection process, we selected a set of mechanism parameters that realize a ring-loop transplanting trajectory capable of large pick displacement with slow picking (pick loop 47 mm) and a large planting angle (planting angle 80.6°). 【Result】Finally, we compared simulation results with theoretical calculations. The results show that the parameters of the incomplete gear set meet the requirements, and that the mechanism’s motion trajectory and posture are in substantial agreement with theory. 【Conclusion】Prototype tests measured a picking angle of 20.95° and a planting angle of 80.3°, validating the feasibility of the combined-variable transmission-ratio transplanting mechanism design.

【Objective】 To address the issues of poor seedling establishment and uneven population growth in direct-seeded rice in southern China, caused by rice seeds are sown on the soil surface after mechanized direct seeding and are subsequently affected by climatic and ecological conditions. 【Methods】 Based on the principle of simultaneous coverage of rice seeds with powdered organic materials, theoretical analysis of a cam-plate metering and application device was conducted. The key parameters of the cam, discharge rotor, material push plate, and discharge apparatus were determined, and a powdered organic material discharge apparatus was designed. Bench tests were carried out. A prototype rice direct seeder with simultaneous powdered organic material coverage was fabricated, and its field performance was validated through field experiments. 【Results】 The results showed that for the powdered organic materials [organic fertilizer, seedling nursery substrate, nutrient soil A, and nutrient soil B (a 2:1 mixture of nutrient soil A and organic fertilizer)], the coefficient of variation for application rate was below 7.80% at rotational speeds of 33–118 r/min, indicating good application stability. Due to the characteristics of the materials, the coverage thickness gradually decreased with increasing rotational speed, but remained stable. When applying the seedling nursery substrate, the coefficient of variation for coverage thickness fluctuated within a relatively large range of 9.41%–18.67%. When applying organic fertilizer, nutrient soil A, and nutrient soil B, the coefficient of variation for coverage thickness was below 15% in all cases, meeting the agronomic requirements for simultaneous coverage of rice seeds with powdered organic materials. Regression equations for coverage thickness were established, all with fitting degrees exceeding 0.95. Field experiment results showed that for the rice varieties Zhongjiazao 17 and Wufengyou 286, the average emergence rates under the coverage treatment increased by 19.59% and 22.65%, respectively, compared with the non-covered treatment. 【Conclusion】 This apparatus improves the mechanized level of rice cultivation and provide a reference for the design of complete rice direct seeding machines with simultaneous powdered organic material coverage.