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10 November 2024, Volume 38 Issue 6 Previous Issue   
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Reviews and Special Topics

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Research Progress in Mining and Utilization of Rice Blast Resistance Genes YANG Jie, YANG Changdeng, ZENG Yuxiang, HOU Yuxuan, CHEN Tianxiao, LIANG Yan 2024, 38(6): 591-603.  DOI: 10.16819/j.1001-7216.2024.230911 Abstract ( )   HTML ( )   PDF (430KB) ( )   Rice blast is a disease caused by Magnaporthe oryzae, which seriously threatens the yield and quality of rice. At present, breeding disease-resistant varieties is the most economical and effective way to control rice blast, and identifying resistance genes is the key to disease-resistant variety breeding. The review summarized the types of rice blast resistance genes cloned as well as the current mainstream techniques for identifying blast-resistant genes. The application of these genes has been outlined along with future development directions.

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Research Progress in Rice Yield Estimation Method Based on Low-altitude Unmanned Aerial Vehicle Remote Sensing FENG Xiangqian, WANG Aidong, HONG Weiyuan, LI Ziqiu, QIN Jinhua, ZHAN Lichuan, CHEN Lipeng, ZHANG Yunbo, WANG Danying, CHEN Song 2024, 38(6): 604-616.  DOI: 10.16819/j.1001-7216.2024.240103 Abstract ( )   HTML ( )   PDF (993KB) ( )   Rice is one of the primary staple crops. Its yield estimation plays a crucial role in the macro-control of national policies, real-time guidance according to local agricultural conditions, and targeted breeding of elite varieties. Therefore, estimating rice grain yield is of great significance. With the continuous advancement in crop science and interdisciplinary approaches, the methods and models for estimating rice yield have diversified greatly. Concurrently, the development of remote sensing technology, particularly the emergence and popularization of low-altitude Unmanned Aerial Vehicles (UAVs), has led to continuous improvements in intelligent remote sensing methods and their accuracy for rice yield estimation. However, there is a lack of systematic and scientific summarization of intelligent rice yield estimation, specifically utilizing UAV remote sensing. This work provides a comprehensive review of the current mainstream methodologies for estimating rice yield, critically evaluating their advantages and limitations. It then explores the application and future directions of intelligent low-altitude remote sensing technology in rice yield estimation. By analyzing the key characteristic information obtained through remote sensing, the article examines the development of primary yield estimation models. It discusses the challenges and limitations encountered when employing intelligent remote sensing for rice yield estimation. The ultimate goal is to enhance our understanding of rice yield estimation methods and provide a systematic and comprehensive reference for the development of intelligent rice yield estimation techniques.

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Advances in Leaf and Canopy Eco-physiological Characteristics of High Photosynthetic Efficiency Rice Varieties and Their Regulation Mechanisms by Nitrogen YE Miao, MAO Yuxin, ZHANG Dehai, KANG Yuying, YUAN Rong, ZHANG Zujian 2024, 38(6): 617-626.  DOI: 10.16819/j.1001-7216.2024.230402 Abstract ( )   HTML ( )   PDF (2481KB) ( )   Increasing the photosynthetic efficiency of rice is regarded as one of the most promising approaches to further improving rice yield. However, the eco-physiological characteristics of rice varieties with high photosynthetic efficiency are not well understood, both at the single leaf level and the group canopy level. This work reviews the influences of Rubisco enzyme content and activity, leaf nitrogen content, and various leaf morphological and anatomical traits, including stomatal traits, leaf vein traits, and leaf mesophyll anatomical traits on single leaf photosynthesis. It also examines the effects of canopy architecture and canopy light-nitrogen matching on group canopy photosynthesis, as well as their regulation by nitrogen. We summarize the leaf and canopy eco-physiological characteristics of high photosynthetic efficiency rice varieties and their regulation by nitrogen. We conclude that high photosynthetic efficiency rice varieties exhibit high leaf Rubisco and nitrogen contents, high stomatal density, and large stomatal pore size. They also have a large proportion of intercellular airspace, a significant coverage of chloroplasts, a large surface area of mesophyll cells and chloroplasts facing intercellular airspace per leaf area, thin cell walls, high vein density, large vascular diameters of veins, large root surface area, large root diameters, straight leaves, deep leaf color, and more leaves in the lower part of the canopy, along with a high degree of canopy light-nitrogen balance. Increasing nitrogen fertilizer can enhance the content and activity of leaf Rubisco, increase the thickness of the leaf mesophyll layer, improve chloroplast coverage, enlarge the surface area of mesophyll cells and chloroplasts facing intercellular airspace per leaf area, reduce cell wall thickness, increase chlorophyll content, and decrease cell wall content, thereby improving leaf photosynthesis. However, excessive nitrogen application can reduce nitrogen use efficiency, leading to a series of environmental issues such as ammonia volatilization, water eutrophication, and increased N2O emissions.

Research Papers

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Sequence Variation Analysis of the Parthenogeny-inducing Gene BBM1 in Rice WANG Qing, WANG Yanru, ZHANG Xiuli, LÜ Qiming 2024, 38(6): 627-637.  DOI: 10.16819/j.1001-7216.2024.231210 Abstract ( )   HTML ( )   PDF (2276KB) ( )   【Objective】Ectopic expression of BBM1 in rice egg cells can induce parthenogenesis. Exploring superior allelic variants of BBM1 and functionally similar genes is of great significance for heterosis fixation in rice.【Method】By utilizing third-generation sequencing data from 383 core rice accessions, we conducted an analysis of structural variations, sequence polymorphisms, and haplotypes of BBM1. Additionally, we screened for genes with similar sequences and expression patterns to identify functional analogues of BBM1.【Results】Our findings revealed the presence of two copies of the BBM1 gene in three rice accessions, along with MITEs insertion variants observed in two O. rufipogon accessions. The BBM1 sequence exhibited a clear indica-japonica differentiation, with 94.80% of japonica accessions and 3.80% of indica accessions experiencing premature termination due to single base mutations, resulting in the loss of 26 amino acid residues. Furthermore, the coding region of BBM1 is highly conserved, and most rice accessions share the same haplotype. We also identified LOC_Os06g44750 as a candidate gene with a similar sequence and expression pattern to BBM1, which may potentially contribute to inducing parthenogenesis.【Conclusion】This study provides insights into the variation present within the BBM1 gene in rice while also identifying important haplotypes and potential candidate genes with functional similarities. This foundational knowledge serves to enhance the frequency of parthenogenesis in rice.

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Genome-wide Identification and Comprehensive Analysis of IDD Gene Family in Rice ZHONG Zhihu, QIN Lu, LI Zhili, YANG Zhen, HE Xiaopeng, CAI Yicong 2024, 38(6): 638-652.  DOI: 10.16819/j.1001-7216.2024.240101 Abstract ( )   HTML ( )   PDF (8036KB) ( )   【Objective】To clarify the characteristics and verify the expression patterns of IDD gene family members in rice, which are plant-specific transcription factors, in order to further investigate the biological functions of OsIDD.【Method】The IDD family members in rice were identified using Pfam, followed by a comprehensive analysis of their nucleic acid and protein sequence features, protein structure, phylogeny, collinearity, and promoter elements. RT-PCR was employed to verify the expression patterns of the OsIDD gene in various tissues, under different hormone treatments, and in response to various abiotic stresses.【Result】The OsIDD family consists of 15 members falling into three subfamilies, which are unevenly distributed across the chromosomes. All members possess nuclear localization signals and highly conserved ID structural domains at the N-terminus. Multiple sequence alignment and motif analysis indicate that these sequences are relatively conserved among different types. Collinearity analysis with the ZmIDD gene family reveals a high degree of homology between the two species. Microarray and RT-PCR analyses showed that OsIDD is predominantly expressed in the panicle and developing endosperm, with its promoter sequences containing hormone and stress-responsive cis-elements.【Conclusion】A comprehensive analysis of the 15 OsIDD members demonstrated structural conservation, strong collinearity with ZmIDD, and high expression levels in panicle and developing endosperm. These findings suggest that OsIDD may be involved in the response to different hormones and various abiotic stresses.

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Cytoplasmic Source Analysis of Sterile Lines from 5460 Three-line Hybrid Rice Varieties LI Wei, XU Xia, BIAN Ying, ZHANG Xiaobo, FAN Jiongjiong, CHENG Benyi, YANG Shihua, WU Jianli, WEI Xin, ZENG Bo, GONG Junyi 2024, 38(6): 653-664.  DOI: 10.16819/j.1001-7216.2024.231214 Abstract ( )   HTML ( )   PDF (2143KB) ( )   【Objective】The 50 years of three-line hybrid rice breeding also represents 50 years of continuous innovation in the development of three-line cytoplasmic male sterile (CMS) lines. It is important to clarify the cytoplasmic types of three-line hybrid rice sterile lines and their derivative pathways. This understanding will enable the quick establishment of restoration relationships and the accurate tracing of the genealogy of rice sterile lines, ultimately promoting the effective utilization of rice heterosis.【Method】Based on the genealogy of three-line hybrid rice varieties that were nationally and provincially approved from 1974 to 2023 in China, we summarized the genealogy of each sterile cytoplasm and analyzed the utilization in breeding.【Result】Over the past 50 years, there have been 966 male sterile lines with clear cytoplasmic classification among the three-line hybrid rice varieties. These lines were classified into 16 categories based on their respective sterile cytoplasm: wild abortive (WA) type, Indonesian Shuitiangu (ID) type, Boro II (BT) type, Dissi (D) type, K type, Gambiaca (GA) type, dwarf abortive (DA) type, Honglian (HL) type, Javanese rice (LX) type, Wanhui (NX) type, Dongxiang wild rice (D1) type, Guangzhou wild rice (GW) type, Gaozhou wild rice (GZ) type, Zhangpu wild rice (FA) type, Maxie (MX) type, and Y type. The analysis revealed that the WA, ID, and BT types had the highest number of CMS lines, accounting for 78.38% of the total CMS lines and 77.77% of the total three-line hybrid rice varieties. In contrast, the MX, D1, Y, and GZ types had the lowest number of CMS lines, representing only 1.55% of the total CMS lines and 1.15% of the total three-line hybrid rice varieties.【Conclusion】With the continuous creation of parental materials for three-line hybrid rice, the diversity of cytoplasmic sources in sterile lines and the efficiency of breeding utilization have significantly improved. This progress has not only mitigated the potential risks associated with a single CMS cytoplasm but has also enriched the utilization pathways of heterosis in three-line hybrid rice breeding in China.

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Mapping of qChalk8 Controlling Chalky Rice Rate in japonica Rice by Combining QTL-Seq with Molecular Markers DU Yanxiu, SUN Wenyu, YUAN Zeke, ZHANG Qianqian, LI Fuhao, LI Junzhou, SUN Hongzheng 2024, 38(6): 665-671.  DOI: 10.16819/j.1001-7216.2024.231207 Abstract ( )   HTML ( )   PDF (2567KB) ( )   【Objective】Chalkiness is an important characteristic that affects the appearance quality of rice grains. This study aims to use QTL-Seq and molecular marker mapping methods to locate QTLs related to chalky rice rates in japonica rice.【Method】F2 segregating populations were constructed using the japonica germplasm Lamujia with a high chalky rice rate and the japonica variety Shuijing 3 with a low chalky rice rate. Two independent F2 populations were planted in Yuanyang, Henan Province, and Sanya, Hainan Province, respectively. The single-plant chalky rice rate was examined, and extreme individuals were pooled for QTL-Seq analysis. Reliable QTLs were then subjected to verification using molecular marker mapping.【Result】QTL-Seq analysis of the two F2 populations revealed the existence of a stable chalky rice rate QTL on chromosome 8, designated as qChalk8. Further molecular marker mapping confined the QTL to a genomic region between 17.6 Mb and 18.5 Mb. The LOD score for qChalk8 was 7.08, and qChalk8 could explain 15.9% of the phenotypic variation.【Conclusion】QTL-Seq and molecular marker mapping successfully identified qChalk8 related to chalky rice rates in japonica rice. The localization of qChalk8 establishes a foundation for further fine mapping and gene cloning of the chalkiness regulatory gene in japonica rice.

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Effects of Nitrogen Application Practice and Row Spacing on Yield and Nitrogen Use Efficiency in japonica Rice With Different Panicle Types LIU Junfeng, MOU Jingyi, ZHAO Hongyan, GUO Shimeng, LI Yimeng, LIANG Chao, ZHOU Chanchan, WANG Shu, HUANG Yuancai 2024, 38(6): 672-684.  DOI: 10.16819/j.1001-7216.2024.240110 Abstract ( )   HTML ( )   PDF (1198KB) ( )   【Objective】This study evaluates the yield and nitrogen use efficiency of japonica rice with various panicle types in response to nitrogen application practice and row spacing. We aim to lay a theoretical basis for high-yield and high-efficiency cultivation of rice in Liaoning Province.【Method】A field experiment was conducted in 2019 and 2020 in Shenyang City, using Shendao 9 (a middle-tillering, mid-sized panicle cultivar), Shendao 505 (a relatively high-tillering, small-sized panicle cultivar), and Shendao 527 (a low-tillering, large-sized panicle cultivar) as entries. The study examined the effects of different nitrogen (N) application patterns, including N0 (zero nitrogen), N1 (farmer's practice ), N2 (reduced basal nitrogen), and N3 (reduced and delayed basal nitrogen application), as well as row spacing, including R1 (30 cm row spacing), R2 (25 cm row spacing), and R3 (wide-narrow row spacing, 40+20 cm), on the yield and nitrogen use efficiency of different panicle types of rice.【Result】The results showed that the nitrogen application pattern, row spacing, and their interaction significantly affected grain yield and nitrogen use efficiency of different panicle types of rice. Under N3, Shendao 9 and Shendao 505 showed increased spikelet number per unit area, seed-setting rate, 1000-grain weight, dry matter accumulation, nitrogen accumulation, partial factor productivity (PFPN), agronomic efficiency (AEN), and apparent recovery efficiency (REN), leading to improvements in yield and nitrogen use efficiency. Shendao 527 achieved high yield under N1 and realized high efficiency under N2. In terms of row spacing, yield, spikelet number per unit area, dry matter accumulation, nitrogen accumulation, PFPN, AEN, and REN were all highest in R2. Shendao 9 and Shendao 505 obtained the highest yield under N3R2, with yield increases of 18.53% and 14.27%, dry matter accumulation increases of 18.38% and 22.47%, nitrogen accumulation increases of 37.22% and 29.15%, PFPN increases of 39.30% and 34.25%, AEN increases of 52.59% and 26.73%, REN increases of 27.65% and 17.70%, and a reduction in the contribution rate of soil nitrogen (CRSN) by 15.75% and 8.16% compared to their respective N1R1. Shendao 527 had a higher yield with no significant differences among N1R1, N1R2, and N2R2, but N2R2 performed better in dry matter accumulation, nitrogen accumulation, and nitrogen utilization.【Conclusion】Therefore, the optimal combination of nitrogen application pattern and row spacing for Shendao 9 and Shendao 505 is reduced and delayed basal nitrogen application with 25 cm row spacing. For Shendao 527, the optimal condition is reduced basal nitrogen applicaton with 25 cm row spacing, allowing all three cultivars to achieve high yield and improved nitrogen utilization.

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Effects of 2,4-Epibrassinolide on Root Growth and Physiological Characteristics of Rice Seedlings Raised in Biochar Substrate WU Xiang, ZHANG Yikai, ZHANG Peng, MA Xinling, CHEN Yulin, CHEN Huizhe, ZHANG Yuping, XIANG Jing, WANG Yaliang, WANG Zhigang, LI Liangtao 2024, 38(6): 685-694.  DOI: 10.16819/j.1001-7216.2024.240503 Abstract ( )   HTML ( )   PDF (2235KB) ( )   【Objective】The improved knotting ability of roots enhances the efficiency and quality of mechanical transplanting. This study investigates the effects and mechanisms of 2,4-epibrassinolide (EBR) on rice root growth in rice straw biochar substrate.【Method】The effects of different concentrations of EBR on the root growth and physiological characteristics of rice seedlings grown in biochar substrate prepared at 300°C were studied using Yongyou 538 as the experimental material.【Result】When EBR was added to the biochar substrate, the root cohesion of rice seedlings increased by 4.13% to 22.46%, and root activity increased by 0.93 to 1.65 times, which improved the stress resistance of rice and promoted root growth. The addition of EBR to the substrate significantly increased the activities of antioxidant protective enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in rice seedlings. It also decreased the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), while increasing the contents of soluble sugar and soluble protein in the seedlings. The expression levels of OsCu/Zn-SOD1, OsCu/Zn-SOD2, OsCAT1, and OsCAT2 genes in the roots and leaves of rice treated with EBR were significantly higher than those in the control group.【Conclusion】When the concentration of EBR was between 1.0 and 1.5 mg/kg in the biochar substrate, root growth of rice seedlings was promoted, enzyme activities of the antioxidant system were enhanced, and the expression of related genes in the seedlings was improved. Additionally, the contents of MDA and H2O2 in the plants were reduced, leading to improved root growth and knotting ability of rice seedlings, thereby promoting the formation of healthy seedlings.

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Effect of Side-deep Fertilization on Yield, Nutrient Uptake and Economic Benefits of Rice CAO Yudong, WU Penghao, DAI Zhigang, WANG Guibing, HE Shuai, GONG Ximin, LI Xiaokun 2024, 38(6): 695-708.  DOI: 10.16819/j.1001-7216.2024.240109 Abstract ( )   HTML ( )   PDF (1378KB) ( )   【Objective】To clarify the effects of side-deep fertilization technology on rice yield, yield components, nutrient absorption, fertilizer utilization, and economic benefits, with a view to providing a scientific basis for the large-scale popularization and application of rice-specific fertilizers and side-deep fertilization technology.【Methods】Field trials were conducted in six pilot counties in Hubei Province in 2020 and nine pilot counties in Hubei Province in 2021, with three treatments: 1) no fertilization (T1); 2) conventional fertilization (T2); and 3) side-deep fertilization (T3). The study analyzed the effects of different fertilization treatments on rice yield, yield component factors, nutrient uptake, fertilizer utilization, and economic benefits.【Results】1) Fertilizer treatments in all pilot counties significantly increased rice yield, with yield increase averaging 37.42% and 51.61% in T2 and T3 respectively, compared to the T1 treatment. The T3 treatment significantly increased yields by an average of 9.81% compared to the T2 treatment. The results for yield component factors showed that side-deep fertilization could significantly increase the average number of effective panicle of rice by 3.58% compared to the T2 treatment. There were differences in the yield increase effects of fertilization treatments across different experimental sites, with a coefficient of variation of 59.54%. This variation may be related to the physical and chemical properties of the basic soil at the experimental sites. The analysis indicates that the yield increase effect of side-deep fertilization is highly significantly positively correlated with the organic matter content in the soil. Side-deep fertilization significantly increased the nutrient uptake and fertilizer utilization of rice. Compared to the T2 treatment, the nutrient uptake of nitrogen, phosphorus, and potassium in the T3 treatment increased by an average of 9.65%, 7.51%, and 12.79%, respectively. The Partial factor productivity, agronomic efficiency, and physiological utilization increased by an average of 10.34%, 37.90%, and 3.28%, respectively. The side-deep fertilization technique significantly improved the economic benefits of rice cultivation. Compared to the T2 treatment, the average increase in rice production and input ratio in the T3 treatment was 7.65%, with an average increase in rice yield of 2504 yuan/hm². The main sources of this yield increase were the higher yield and reduced labor costs.【Conclusion】Side-deep fertilization technology significantly improves rice yield and fertilizer utilization, increases economic benefits, and achieves enhanced yield, efficiency, cost savings, and income. Additionally, the effect of side-deep fertilization on yield becomes more significant with increasing soil organic matter content. Therefore, this technology can be widely promoted and applied in the main rice planting areas of Hubei Province, particularly in high-fertility soils.

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Analysis on Appearance and Cooking Taste Quality Characteristics of Different Types of japonica Rice in Jianghuai Rice-growing Area YAO Shu, CHEN Tao, ZHAO Chunfang, ZHOU Lihui, ZHAO Ling, LIANG Wenhua, HAO Lei, LU Kai, ZHU Zhen, ZHAO Qingyong, GUAN Ju, WANG Cailin, ZHANG Yadong 2024, 38(6): 709-718.  DOI: 10.16819/j.1001-7216.2024.240310 Abstract ( )   HTML ( )   PDF (430KB) ( )   【Objective】This study investigates the differences in physical and chemical properties related to the appearance and taste of widely-grown and newly bred high-quality japonica rice varieties in the Jianghuai rice-growing area. The aim is to provide a theoretical basis for selecting suitable varieties for planting and for the improvement of high-quality japonica rice varieties.【Method】The study utilized 26 high-quality japonica rice varieties that have been popularized and applied in the Jianghuai Area in recent years. These varieties were categorized into two groups: semi-waxy japonica rice and common japonica rice. The differences in physical and chemical indicators related to appearance and taste among the different types of japonica rice were compared, and the relationship between various physical and chemical indexes of rice and taste quality was analyzed.【Result】1) In terms of appearance quality, significant differences were observed in chalky rice percentage, chalkiness degree, and transparency between the two types of japonica rice varieties. The transparency of semi-waxy japonica rice was significantly lower than that of common japonica rice. 2) Regarding starch physicochemical properties, the amylose content, gel consistency, hot paste viscosity, cold paste viscosity, and setback of semi-waxy japonica rice were significantly lower than those of common japonica rice, while the breakdown value was significantly higher than that of common japonica rice. 3) In terms of rice taste value index, there was no significant difference in the appearance of rice between semi-waxy japonica rice and common japonica rice. However, the viscosity, hardness, balance, and taste value of semi-waxy japonica rice were significantly higher than those of common japonica rice. 4) Correlation analysis indicated that the length-width ratio of whole rice in the appearance quality, amylose content in various physical and chemical indicators, gel consistency, and gelatinization temperature, as well as the appearance and hardness of rice taste value parameters, are closely related to rice taste.【Conclusion】The appearance and cooking taste quality of the two different types of japonica rice varieties were significantly different. Common japonica rice exhibited a crystal-clear appearance, while semi-waxy japonica rice appeared relatively turbid. Common japonica rice had higher amylose content and gelatinization temperature, along with lower gel consistency, disintegration value, and taste value. Conversely, semi-waxy japonica rice had lower amylose content and gelatinization temperature, but higher gel consistency, disintegration value, and taste value.