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28 November 2024, Volume 31 Issue 6 Previous Issue   
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Letters

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Efficient Breeding of Early-Maturing Rice Cultivar by Editing Hd6 via CRISPR/Cas9 Chen Zhihui, Tao Yajun, Xu Yang, Wu Jingjing, Wang Fangquan, Li Wenqi, Jiang Yanjie, Fan Fangjun, Li Xia, Zhu Jianping, Zhu Qian-Hao, Yang Jie 2024, 31(6): 629-633.  DOI: 10.1016/j.rsci.2024.06.007 Abstract ( )   HTML ( )   PDF (3932KB) ( )

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Immune Sensor Xa21 Regulates Bacterial Leaf Blight Infection in Seven Rice Cultivars from Myanmar Nay Chi Aye, Rizwana Begum Syed Nabi, Muhammad Shahid, Nkulu Kabange Rolly, Rupesh Tayade, Lee-Bong Choon, Adil Hussain, Byung-Wook Yun 2024, 31(6): 634-637.  DOI: 10.1016/j.rsci.2024.06.008 Abstract ( )   HTML ( )   PDF (2370KB) ( )

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Does Financial Inclusion Influence Economic Efficiency of Rice Farming? Evidence from Ogun State, Nigeria Shakirat B. Ibrahim, Raheem O. Aminu, Aisha O. Arowolo, Opeyemi O. Okanlawon, Afeez A. Adegbola 2024, 31(6): 638-642.  DOI: 10.1016/j.rsci.2024.10.001 Abstract ( )   HTML ( )   PDF (866KB) ( )

Reviews

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Synergy in Rice Immunity: Exploring Strategies of Coordinated Disease Defense Through Receptor-Like Kinases and Receptor- Like Cytoplasmic Kinases Pei Mengtian, Cao Yingying, Xie Xuze, Cao Ying, Chen Jia, Zhang Xi, Wang Zonghua, Lu Guodong, Zhang Shenghang 2024, 31(6): 643-658.  DOI: 10.1016/j.rsci.2024.07.002 Abstract ( )   HTML ( )   PDF (2650KB) ( )   Receptor-like kinases (RLKs) and receptor-like cytoplasmic kinases (RLCKs) play an indispensable role in the perception and transmission of extracellular signals in plants. In rice, these kinases actively participate in immune responses against a variety of pathogens, including fungi, bacteria, and viruses. However, research on the specific response mechanisms and the spectrum of different kinase activities against various pathogens remains insufficient. This review provides an in-depth and comprehensive overview of the types and functions of RLKs and RLCKs involved in disease resistance, emphasizing the central role of certain RLKs and RLCKs in the plant immune system. These kinases can recognize specific molecular patterns of pathogens and rapidly initiate an immune response in rice. Furthermore, the activity and functional regulation of these key kinases are tightly controlled by various post-translational modifications, such as phosphorylation and ubiquitination. This meticulous regulation ensures that the rice immune system’s response is both precise and timely, effectively balancing the intensity of the immune response and preventing potential issues caused by either hyperactivity or insufficiency. By synthesizing current research findings, this review not only broadens our understanding of the role of RLKs and RLCKs in plant immunity but also provides new perspectives and strategies for future research on disease resistance breeding in rice. Future studies are expected to delve deeper into the signaling networks and regulatory mechanisms of these kinases, exploring their potential in agricultural production to develop rice varieties with enhanced disease resistance.

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Breeding Resilience: Exploring Lodging Resistance Mechanisms in Rice Durga Prasad Mullangie, Kalaimagal Thiyagarajan, Manonmani Swaminathan, Jagadeesan Ramalingam, Sritharan Natarajan, Senthilkumar Govindan 2024, 31(6): 659-672.  DOI: 10.1016/j.rsci.2024.08.002 Abstract ( )   HTML ( )   PDF (6882KB) ( )   Lodging is more than just plants falling over; it incurs significant economic losses for farmers leading to a decrease in both yield and quality of the final produce. Human management practices, such as dense sowing, excessive nitrogen fertilizer applications, inappropriate sowing dates, and upland rice cultivation, exacerbate the risk of lodging in rice. While breeders have developed high-yielding rice varieties utilizing the sd1 gene, relying solely on this gene is insufficient to enhance lodging resistance. Identifying the traits that contribute to lodging resistance is crucial. Key factors include biochemical, anatomical, and morphological traits, such as the levels of lignin, cellulose, hemicellulose, silicon, and potassium, along with the number and area of vascular bundles and the thickness, diameter, and length of the culm. Moreover, markers associated with lodging-related genes, like SCM2, SCM3, SCM4, and prl4, can be utilized effectively in marker-assisted backcrossing to develop rice varieties with desirable culm traits. This literature review aims to aid rice breeders in addressing the issue of lodging by examining traits that influence lodging resistance, developing phenotyping strategies for these traits, identifying suitable instrumentation, exploring methods for screening lodging-resistant plants, understanding the mathematical relationships involved, and considering molecular breeding aspects for pyramiding genes related to lodging.

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Progress on Molecular Mechanism of Heat Tolerance in Rice Fu Yiwei, Wu Jiayelu, Wu Mingming, Ye Shenghai, Zhai Rongrong, Ye Jing, Zhu Guofu, Yu Faming, Lu Yanting, Zhang Xiaoming 2024, 31(6): 673-687.  DOI: 10.1016/j.rsci.2024.07.001 Abstract ( )   HTML ( )   PDF (2368KB) ( )   Rice (Oryza sativa L.) is a major food crop in China, and its high and stable yield is crucial for ensuring food security in the country. However, over the past few years, extreme weather events induced by global climate change have impacted rice growth. For example, the effects of heat stress on rice quality and yield have been significant. Therefore, it is fundamental to conduct in-depth research on the heat-tolerance mechanisms of rice and to cultivate superior new thermotolerant rice varieties. This review summarizes the adverse effects of high temperatures on rice growth at various stages, the heat-tolerance mechanisms in rice, and the heat-tolerance genes and QTLs that have been identified in recent years. We also discuss strategies to enhance the heat tolerance of rice, offering new insights for rice breeding research.

Research Papers

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Histone Acetyltransferase GCN5 Regulates Rice Growth and Development and Enhances Salt Tolerance Xue Chao, Zhao Xinru, Chen Xu, Cai Xingjing, Hu Yingying, Li Xiya, Zhou Yong, Gong Zhiyun 2024, 31(6): 688-699.  DOI: 10.1016/j.rsci.2024.06.002 Abstract ( )   HTML ( )   PDF (12220KB) ( )   Histone acetylation is indispensable in the process of crops resisting abiotic stress, which is jointly catalyzed by histone acetyltransferases and deacetylases. However, the mechanism of regulating salt tolerance through histone acetyltransferase GCN5 is still unclear. We revealed that GCN5 can catalyze the acetylation of canonical H3 and H4 lysine residues both in vivo and in vitro in rice. The knockout mutants and RNA interference lines of OsGCN5 exhibited severe growth inhibition and defects in salt tolerance, while the over-expression of OsGCN5 enhanced the salt tolerance of rice seedlings, indicating that OsGCN5 positively regulated the response of rice to salt stress. RNA-seq analysis suggested OsGCN5 may positively regulate the salt tolerance of rice by inhibiting the expression of OsHKT2;1 or other salt-responsive genes. Taken together, our study indicated that GCN5 plays a key role in enhancing salt tolerance in rice.

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Molecular Evolution of Rice Blast Resistance Gene bsr-d1 Li Wei, Zhang Mengchen, Yang Yaolong, Weng Lin, Hu Peisong, Wei Xinghua 2024, 31(6): 700-711.  DOI: 10.1016/j.rsci.2024.08.004 Abstract ( )   HTML ( )   PDF (5443KB) ( )   Rice blast, caused by the fungus Magnaporthe oryzae, reduces rice yields by 10% to 35%. Incorporating blast resistance genes into breeding programs is an effective strategy to combat this disease. Understanding the genetic variants that confer resistance is crucial to this strategy. The gene Bsr-d1 encodes a C2H2-like transcription factor, and its recessive allele confers broad-spectrum resistance against infections by various strains of M. oryzae. In this study, we investigated the molecular evolution of the rice blast resistance gene bsr-d1 in a representative population consisting of 827 cultivated and wild rice accessions. Our results revealed that wild rice exhibited significantly higher nucleotide diversity, with polymorphic regions primarily concentrated in the promoter region, in contrast to indica and japonica rice varieties. The Bsr-d1 gene displayed significant differentiation between indica and japonica rice varieties, with the bsr-d1 resistance allele being unique to indica rice. Haplotype network and phylogenetic analyses suggested that the bsr-d1 resistance allele most likely originated from Oryza nivara in the region adjacent to the Indian Peninsula and the Indochina Peninsula. Moreover, we explored the utilization of bsr-d1 resistance alleles in China and designed a pair of DNA primers based on the polymorphic sites for the detection of the bsr-d1 resistance gene. In summary, our study uncovering the origin and evolution of bsr-d1 will enhance our understanding of resistance gene variation and expedite the resistance breeding process.

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Mixed-Oligosaccharides Promote Seedling Growth of Direct-Seeded Rice under Salt and Alkaline Stress Yang Yigang, Xu Ya’nan, Bai Yeran, Zhang Yuanpei, Han Wei, Makoto Saito, Lü Guohua, Song Jiqing, Bai Wenbo 2024, 31(6): 712-724.  DOI: 10.1016/j.rsci.2024.08.001 Abstract ( )   HTML ( )   PDF (1714KB) ( )   Rice direct seeding technology is an appealing alternative to traditional transplanting because it conserves labor and irrigation resources. Nevertheless, there are two main issues, salt stress and alkaline stress, which contribute to poor emergence and seedling growth, thereby preventing the widespread adoption and application of this technique in the Ningxia Region of China. Therefore, to determine whether germination can be promoted by mixed-oligosaccharide (KP) priming (in which seeds are soaked in a KP solution before sowing) under salt and alkaline stress, a proteomics study was performed. KP-priming significantly mitigated abiotic stress, such as salt and alkaline stress, by inhibiting root elongation, ultimately improving seedling establishment. By comparing the proteomics analyses, we found that energy metabolic pathway was a vital factor in KP-priming, which explains the alleviation of salt and alkaline stress. Key proteins involved in starch mobilization, pyruvate mobilization, and ATP synthesis, were up-regulated by KP-priming, significantly blocking salt and alkaline-triggered starch accumulation while enhancing pyruvate metabolism. KP-priming also up-regulated ATP synthase to improve energy efficiency, thereby improving ATP production. In addition, it enhanced antioxidant enzymatic activities and reduced the accumulation of reactive oxygen species. All of these factors contributed to a better understanding of the energy regulatory pathway enhanced by KP-priming, which mediated the promotion of growth under salt and alkaline conditions. Thus, this study demonstrated that KP-priming can improve rice seed germination under salt and alkaline stress by altering energy metabolism.

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Simulating Responses of Rice Yield and Nitrogen Fates to Ground Cover Rice Production System under Different Types of Precipitation Years Ren Jian, Hu Kelin, Feng Puyu, William D. Batchelor, Liu Haitao, Lü Shihua 2024, 31(6): 725-739.  DOI: 10.1016/j.rsci.2024.06.004 Abstract ( )   HTML ( )   PDF (5041KB) ( )   The Ground Cover Rice Production System (GCRPS) has considerable potential for securing rice production in hilly areas. However, its impact on yields and nitrogen (N) fates remains uncertain under varying rainfall conditions. A two-year field experiment (2021-2022) was conducted in Ziyang, Sichuan Province, located in the hilly areas of Southwest China. The experiment included two cultivation methods: conventional flooding paddy (Paddy, W1) and GCRPS (W2). These methods were combined with three N management practices: N1 (no-N fertilizer), N2 (135 kg/hm2 urea as a base fertilizer in both W1 and W2), and N3 (135 kg/hm2 urea with split application for W1 and 67.5 kg/hm2 urea and chicken manure separately for W2). The WHCNS (Soil Water Heat Carbon Nitrogen Simulator) model was calibrated and validated to simulate ponding water depth, soil water storage, soil mineral N content, leaf area index, aboveground dry matter, crop N uptake, and rice yield. Subsequently, this model was used to simulate the responses of rice yield and N fates to GCRPS under different types of precipitation years using meteorological data from 1980 to 2018. The results indicated that the WHCNS model performed well in simulating crop growth and N fates for both Paddy and GCRPS. Compared with Paddy, GCRPS reduced N leaching (35.1%-54.9%), ammonia volatilization (0.7%-13.6%), N runoff (71.1%-83.5%), denitrification (3.8%-6.7%), and total N loss (33.8%-56.9%) for all precipitation year types. However, GCRPS reduced crop N uptake and yield during wet years, while increasing crop N uptake and yield during dry and normal years. Fertilizer application reduced the stability and sustainability of rice yield in wet years, but increased the stability and sustainability of rice yield in dry and normal years. In conclusion, GCRPS is more suitable for normal and dry years in the study region, leading to increased rice yield and reduced N loss.

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Compound Microbial Agent Improves Soil Redox Status to Reduce Methane Emissions from Paddy Fields Tao Yi, Xiao Deshun, Ye Chang, Liu Kancheng, Tang Xinxin, Ma Hengyu, Chu Guang, Yu Kai, Xu Chunmei, Wang Danying 2024, 31(6): 740-750.  DOI: 10.1016/j.rsci.2024.05.002 Abstract ( )   HTML ( )   PDF (3113KB) ( )   Paddy fields are considered a major source of methane (CH4) emissions. Aerobic irrigation methods have proven to be efficacious in mitigating CH4 emissions in paddy cultivation. The promising role of compound microbial agents in refining the rhizospheric ecosystem suggests their potential as novel agents in reducing CH4 emissions from paddy fields. To explore a new method of using compound microbial agents to reduce CH4 emissions, we conducted pot and field experiments over the period of 2022‒2023. We measured CH4 flux, the redox potential (Eh) of the soil, the concentration of dissolved oxygen (DO) in the floodwater, and the gene abundance of both methanogens (mcrA) and methanotrophs (pmoA). The results showed that the application of the compound microbial agent led to a significant increase in the DO levels within the floodwater and an increase of 9.26% to 35.01% in the Eh of the tillage soil. Furthermore, the abundance of pmoA increased by 31.20%, while the mcrA/pmoA ratio decreased by 25.96% at the maximum tillering stage. Applying 45−75 kg/hm2 of the compound microbial agent before transplanting resulted in a reduction of cumulative CH4 emissions from paddy fields by 17.49% in single- cropped rice and 43.54% to 50.27% in double-cropped late rice during the tillering stage. Correlation analysis indicated that CH4 flux was significantly negatively correlated with pmoA gene abundance and soil Eh, and positively related to the mcrA/pmoA ratio. Additionally, soil Eh was significantly positively correlated with pmoA gene abundance, suggesting that paddy soil Eh indirectly affected CH4 flux by influencing the pmoA gene abundance. In conclusion, the pre-planting application of the compound microbial agent at a rate of 45‒75 kg/hm2 can enhance the Eh in the rhizosphere and increase the abundance of the pmoA gene, thereby reducing CH4 emissions from paddy fields during the tillering stage of rice growth.

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Applying Boron Fertilizer at Different Growth Stages Promotes Boron Uptake and Productivity in Rice Sitthikorn Bodeerath, Jeeraporn Veeradittakit, Sansanee Jamjod, Chanakan Prom-U-Thai 2024, 31(6): 751-760.  DOI: 10.1016/j.rsci.2024.08.007 Abstract ( )   HTML ( )   PDF (2590KB) ( )   Boron (B) is an essential micronutrient for plant growth and yield. We investigated the optimal growth stage for B fertilizer application to improve rice production. The study was conducted using a 2 × 4 factorial design in a randomized complete block during the rainy season of 2022. We utilized two premium Thai rice varieties Khao Dawk Mali 105 (KDML105) and Pathum Thani 1 (PTT1), and four soil B fertilizer treatments: a control (no B application), B application at the tillering stage, B application at the flowering stage, and B application at both the tillering and flowering stages. The results showed that the application of B fertilizer at the flowering stage and at both the tillering and flowering stages increased grain yield of KDML105 by 25.0% and 34.0%, respectively. In contrast, the grain yield of PTT1 showed no response to B application. The increased grain yield of KDML105 was attributed to an increased number of panicles per plant and a higher filled grain rate, which was due to the elevated B concentration in all plant parts and the total B uptake, particularly when B was applied at the flowering and tillering stages. Notably, B application increased the fertilized grain rates and reduced the proportion of unfertilized grains, a phenomenon that corresponded with the increased B concentration across all plant parts. The total B uptake ranged from 5.11 to 15.85 mg/m2 in KDML105 and from 8.37 to 24.26 mg/m2 in PTT1, with the highest total B uptake observed when B was applied at both the tillering and flowering stages for both rice varieties.