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10 September 2023, Volume 37 Issue 5 Previous Issue    Next Issue
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Reviews and Special Topics

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Advances in the Molecular Mechanism of Rice Plant Type LAN Jinsong, ZHUANG Hui 2023, 37(5): 449-458.  DOI: 10.16819/j.1001-7216.2023.221102 Abstract ( )   HTML ( )   PDF (401KB) ( )   The plant type of rice is one of the major factors determining rice yield. The ideotype of high-yielding rice cultivar is an important way to increase rice yield potential in rice breeding. Dwarf breeding in the 1950s and hybrid rice breeding in the 1970s are two revolutions in rice yield. However, the growth rate of rice yield has slowed down significantly in recent years. The third yield breakthrough depends on the super-high-yield breeding that combines ideotype with heterosis. We briefly reviewed the advances in the regulation mechanism of rice plant architecture, focusing on the progress achieved in leaf, panicle, grain and other aspects, and looked forward to the future research trends rice ideotype. It will lay a solid foundation for improving rice plant type and further increasing rice yield through molecular breeding.

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Mechanisms Behind Aleurone Development in Cereals and Its Application in Breeding WANG Tengjiao, CHEN Chen 2023, 37(5): 459-469.  DOI: 10.16819/j.1001-7216.2023.230105 Abstract ( )   HTML ( )   PDF (4022KB) ( )   The outmost layer of endosperm cells differentiates into alleurone cells during seed development, which distinguish themselves from the inner endosperm cells morphologically and physiologically. For example, the aleurone layer is rich in proteins, lipids, vitamins, dietary fibers and mineral elements. The aleurone cells secrete amylase and protease for hydrolyzing reserves accumulated in the endosperm. Several key genes involved in the regulation of aleurone cell differentiation and development have been identified with the mutants showing aleurone defects, deepening our understanding of the aleurone cell fate determination. It has been proposed that increasing the number of aleurone layers may help improve nutritional quality of cereals. In this review, taking rice as an example, we summarized the differentiation and development regulations of aleurone in cereals. We also discussed the potentials, issues and possible solutions for breeding high-nutrition cereals by improving the aleurone-related traits.

Research Papers

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Genetic Dissection of Broad Spectrum Resistance of the Rice Maintainer Ganxiang B CHEN Mingliang, XIONG Wentao, SHEN Yumin, XIONG Huanjin, LUO Shiyou, WU Xiaoyan, HU Lanxiang, XIAO Yeqing 2023, 37(5): 470-477.  DOI: 10.16819/j.1001-7216.2023.221105 Abstract ( )   HTML ( )   PDF (916KB) ( )   【Objective】 Ganxiang B is a WA type rice maintainer line developed by the Rice Research Institute of Jiangxi Academy of Agricultural Sciences. It shows broad spectrum resistance against rice blast in Jiangxi, Fujian, Guizhou, Hubei, and Zhejiang Provinces. Genetic analysis of blast resistance loci in Ganxiang B will contribute to the future work for blast resistance breeding. 【Method】 The rice blast resistance loci in Ganxiang B were analyzed by genome comparison between resistant and susceptible lines, marker detection of rice blast resistance locus, resistance gene sequencing, and phenotypic identification of segment substitution lines. 【Results】 There were resistance genes Pish, Pia, and Pita in Ganxiang B. After introgressed with Pish, the blast resistance of highly susceptible line was significantly enhanced. However, after introgressed with Pita or Pia, the resistance was slightly enhanced or remained unchanged.【Conclusion】 Ganxiang B carries several blast resistance genes. Among them, Pish is the main resistant gene, showing broad resistance to rice blast.

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Development of Aromatic Salt-tolerant Rice Based on CRISPR/Cas9 Technology LI Jingfang, WEN Shuyue, ZHAO Lijun, CHEN Tingmu, ZHOU Zhenling, SUN Zhiguang, LIU Yan, CHEN Haiyuan, ZHANG Yunhui, CHI Ming, XING Yungao, XU Bo, XU Dayong, WANG Baoxiang 2023, 37(5): 478-485.  DOI: 10.16819/j.1001-7216.2023.220907 Abstract ( )   HTML ( )   PDF (1424KB) ( )   【Objective】 It is of importance to promote salt-tolerant and fragrant rice breeding. We obtained transgene free homozygous rice materials with salt-tolerance and fragrance by CRISPR/Cas9-mediated editing of Badh2 and OsRR22 in japonica variety Lianjing 11. 【Method】 Target sites were designed according to knockout efficiency of editing sites in Badh2 and OsRR22 gene sequence. The pH-Ubi-Badh2-OsRR22 knockout vector was constructed and transferred into the recipient variety Lianjing 11 by the Agrobacterium-mediated technology. PCR detection for hygromycin, Cas9 marker and target gene sequencing were performed in the transgenic progenies to obtain badh2-osrr22 homozygous lines without exogenous gene insertion. The seed traits and salt tolerance at seedling stage were analyzed. 【Result】 Compared with the background material Lianjing 11, the 2-AP content of T2 significantly increased. After treated with 128 mmol/L NaCl solution for 14 days, the seedling height, the fresh and the dry weight of T2 line 21-30 increased by 15.2%, 45.2% and 13.2%, respectively. 【Conclusion】 The successful editing of Badh2 and OsRR22 by CRISPR/Cas9 technology developed aromatic salt-tolerant homozygous lines without exogenous gene insertion, speeding up the breeding process of pyramiding multiple traits in rice.

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Effects of Silicon on Antioxidant Enzyme System and Expression Levels of Genes Related to Cd2+ Uptake and Transportation in Rice Seedlings Under Cadmium Stress HUANG Qina, XU Youxiang, LIN Guanghao, DANG Hongyang, ZHENG Zhenquan, ZHANG Yan, WANG Han, SHAO Guosheng, YIN Xianyuan 2023, 37(5): 486-496.  DOI: 10.16819/j.1001-7216.2023.230203 Abstract ( )   HTML ( )   PDF (800KB) ( )   【Objective】 To elucidate the effects of exogenous silicon (Si) on plant height, dry weight, antioxidant enzyme system, and the expression levels of Cd2+ related genes in rice under cadmium (Cd) stress, so as to lay a theoretical basis for clarifying the mechanism of Si in alleviating Cd toxicity in rice. 【Method】 Indica rice Fupin 36 (FP36) and Zhongjiazao 17 (ZJZ17) were hydrocultured under two Cd2+ concentrations (0, 5 µmol/L) and three Si treatments (0, 10 µmol/L, 1 mmol/L). The agronomic traits, antioxidant enzyme activities, and the expression levels of Cd2+ uptake/transport-related genes were analyzed. 【Result】 Cadmium stress significantly inhibited the agronomic traits and activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbic acid oxidase) of ZJZ17 and FP36, but exogenous Si addition could effectively alleviate the toxicity of Cd to rice, and enhance the activities of antioxidant enzymes. Moreover, 1 mmol/L Si treatment exerted a better alleviating effect on Cd stress than 10 µmol/L Si. In addition, Cd stress also affected the contents of soluble protein and malondialdehyde (MDA) in rice, while Si exposure increased soluble protein content but decreased the MDA content, respectively. Cd intervention significantly increased Cd content in different tissues of FP36 and ZJZ17, and its accumulation in roots was significantly higher than that in shoots. However, there was no significant difference in Cd content in rice plants under 10 µmol/L Si addition; and Cd accumulation in rice was significantly decreased as exposed to 1 mmol/L Si at 5 µmol/L Cd2+ concentration, indicating that the Cd accumulation in shoots was higher than that in roots. The expression levels of Cd2+ uptake/transport-related genes followed different trends as subjected to Cd stress and Si treatments. Compared with zero-Cd treatment, the expression levels of OsNRAMP1, OsIRT1 and OsHMA2 were up-regulated under Cd stress, while OsNRAMP5 expression tended to be down-regulated, and the expression level of OsHMA3 remained unchanged. Moreover, the expression levels of OsNRAMP1, OsNRAMP5, OsIRT1, OsHMA2, OsHMA3 were significantly decreased at 1 mmol/L Si concentration. 【Conclusion】 Silicon alleviates the toxicity of Cd to rice by improving the agronomic traits, activating the antioxidant system, and regulating the expression levels of Cd2+ uptake/transport-related genes.

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Characterization and Gene Mapping of a Glume Lesion Mimic Mutant glmm1 in Rice XU Huan, ZHOU Tao, SUN Yue, WANG Mumei, YANG Yachun, MA Hui, LI Hao, XU Dawei, ZHOU Hai, YANG Jianbo, NI Jinlong 2023, 37(5): 497-506.  DOI: 10.16819/j.1001-7216.2023.221201 Abstract ( )   HTML ( )   PDF (47940KB) ( )   【Objective】 The aim of this study is to identify and map the glume lesion mimics mutant gene in rice, and to lay a foundation for gene cloning and molecular mechanism research. 【Method】 Agronomic traits analysis, scanning electron microscopy observation, DAB staining, and total silicon content determination were performed on the wild-type material LR005 and the glume lesion mimics mutant glmm1 obtained through EMS mutagenesis. The F2 population derived from glmm1 and L422 was used for genetic analysis, and gene mapping by map-based cloning and BSA-seq method. 【Result】 The mutant gradually showed brown spots on the glumes and leaves 10 days after heading, and the glumes were completely brown at mature stage. Compared with the wild type, the mutant showed highly significant reductions in plant height, panicle length, total number of grains per panicle, seed setting rate and 1000-grain weight. DAB staining showed that the glmm1 glumes and leaves had increased ROS(reactive oxygen species) content; Scanning electron microscopy observation showed that the siliceous cells on the surface of the mutant glumes and leaves wrinkled. The genetic analysis showed that the glume lesion mimics phenotype of glmm1 was controlled by a pair of recessive genes. Using the F2 segregating population of glmm1 and L422, GLMM1 was localized to a 68-kb interval containing 10 genes on chromosome 2 by map-based cloning and BSA-seq. Sequence analysis revealed only one SNP in this interval, which located in the fifth exon of the gene Lsi1 (LOC_Os02g51110), resulting in a substitution of Ile with Thr. The reduced accumulation of glmm1 silicon was found by measuring total silicon content of the glumes and leaves, suggesting that glmm1 may be a mutant allele of Lsi1. 【Conclusion】 glmm1 is a new mutant allele of Lsi1, which causes a reduction in silicon content and accumulation of reactive oxygen species in plants, resulting in brown spots on glumes and leaves.

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Identification of QTL for Milling and Appearance Quality Traits in Rice (Oryza sativa L.) YAO Xiaoyun, CHEN Chunlian, XIONG Yunhua, HUANG Yongping, PENG Zhiqing, LIU Jin, YIN Jianhua 2023, 37(5): 507-517.  DOI: 10.16819/j.1001-7216.2023.220908 Abstract ( )   HTML ( )   PDF (698KB) ( )   【Objective】 Milling and appearance quality(MAQ) are the key factors affecting the production efficiency and commodity value of rice. Exploring the major QTLs for MAQ related traits help further clarify the molecular genetic mechanism of quality traits, which also provides genetic materials for high-quality breeding in rice.【Method】 A recombinant inbred line(RIL) population derived from the cross between Longdao 5 (high-quality japonica) and Zhongyouzao 8 (high-yield indica) was used to identify QTLs for milling and appearance quality traits in multiple environments.【Result】 Thirty-seven QTLs related to processing and appearance quality were detected on 12 chromosomes. 15, 15, and 21 QTLs were found in the three environments, respectively. Only 10 QTLs were stably expressed in two environments, and two QTLs were repeatedly detected in all the three environments. Processing and appearance quality related QTLs showed significant genetic overlap effects. In addition, QTLs of the milling and appearance quality had obvious genetic overlap effect. There were five major QTL clusters on the chromosomes 2, 6, 7, 10 and 11, which had obvious regulatory effects on milling and appearance quality.【Conclusion】 qMAQ7 (qChlak7) is a novel pleiotropic QTL cluster on chromosome 7 between RM1306 and RM420, which exerts obvious regulatory effects on percentage of chalky grains and chalkiness degree. In addition, the epistatic effect plays an important role in the regulation of milling and appearance quality traits, and then the major effect QTL was involved in epistatic interaction effect.

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Effects of Combined Application of Chemical Fertilizers and Nitrogen Reduction on the Yield of Double-cropping Rice and the Risk of Nitrogen and Phosphorus Loss in Field Water in Dongting Lake Area YUAN Pei, ZHOU Xuan, YANG Wei, YIN Lingjie, JIN Tuo, PENG Jianwei, RONG Xiangmin, TIAN Chang 2023, 37(5): 518-528.  DOI: 10.16819/j.1001-7216.2023.221003 Abstract ( )   HTML ( )   PDF (1026KB) ( )   【Objective】 It is very important to explore chemical nitrogen fertilizer reduction and rationing to stabilize rice yield, improve nitrogen use efficiency, reduce the risk of nitrogen and phosphorus loss, and lay a scientific basis for fertilizer reduction in the Dongting Lake double-cropping rice area. 【Method】 The field plot experiment was conducted, and six treatments were set, including no nitrogen fertilizer (CK), conventional fertilizer (CF), 20% nitrogen reduction with borosilicate fertilizer (0.8CF+B/Si), 80% chemical fertilizer+20% organic fertilizer (0.8CF+0.2OM), 80% chemical fertilizer+20% organic fertilizer with nitrogen synergist (0.8CF+0.2OM+N-serve), and 20% organic fertilizer combined with borosilicate fertilizer and nitrogen synergist (0.8CF+0.2OM+B/Si+N-serve). Yield, nitrogen use efficiency, and the risk of nitrogen and phosphorus loss in field water of double-cropping rice were analyzed. 【Result】 The yield of early rice was reduced as compared with CF, while the yield of late rice was increased by 2.02% to 5.03%. The concentrations of total nitrogen, ammonium nitrogen, and nitrate nitrogen in surface water increased with the increase in nitrogen application rate, and the risk of nitrogen loss also increased. Compared with CF treatment, the chemical fertilizer nitrogen reduction and rationing treatment reduced total nitrogen, ammonium nitrogen, and nitrate nitrogen concentrations in early and late rice seasonal field water by 8.08% to 35.05%, 5.88% to 34.22%, and 5.02% to 18.06%, respectively, and 0.8CF+0.2OM+N-serve treatment was the most effective in mitigating the risk of nitrogen loss from field water. One week after nitrogen application was the peak period of nitrogen loss, and then the difference in nitrogen concentration in surface water of each treatment decreased, as did the risk of nitrogen loss. The phosphorus concentration of early and late rice surfaces without nitrogen fertilizer was lower than that of other treatments, while the phosphorus concentration of early and late rice surface water with borosilicate fertilizer was higher than that of other treatments, which aggravated the risk of phosphorus loss in rice surface water. In addition, the combined application of organic fertilizer and nitrogen fertilizer synergists had no obvious effect on phosphorus emission reduction. About 9 days after the application of phosphorus fertilizer was the key period of phosphorus loss, after which the phosphorus concentration of each treatment tended to be consistent and changed smoothly. 【Conclusion】 The substitution of organic fertilizer for nitrogen fertilizer has a lag effect on rice yield. The simultaneous application of nitrogenous synergists with organic fertilizers will weaken the effect of nitrogen synergists in retarding nitrogen fertilizer conversion. Chemical fertilizer nitrogen reduction and rationing is an effective method to reduce nitrogen loss in the surface water of double-cropping rice fields, but its combination with borosilicate fertilizer can increase phosphorus content in the surface water, so it should be applied according to water and fertilizer management.

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Effects of Nitrogen Fertilizer Consumption and Operation on Rice Yield and Its Components in China：A Meta-analysis XIAO Dakang, HU Ren, HAN Tianfu, ZHANG Weifeng, HOU Jun, REN Keyu 2023, 37(5): 529-542.  DOI: 10.16819/j.1001-7216.2023.221111 Abstract ( )   HTML ( )   PDF (2425KB) ( )   【Objective】 Moderate nitrogen (N) fertilizer rate and operation can effectively improve rice yield and N use efficiency. Clarifying the effects of N rate fertilizer rate and operation on rice yield and its components can provide theoretical guidance for high yield and high efficiency for rice. 【Methods】 Based on 119 published articles on N fertilizer management in rice fields, a meta-analysis was conducted to summarize the effects of N management on rice yield and its components under different total N rates, basal fertilizer+tillering fertilizer, topdressing for panicle initiation, planting areas and soil properties, and explored the appropriate measures to improve yield components to get high yield in major Chinese rice production areas. 【Results】 Compared with no N fertilizer application, N fertilizer application can significantly increase the actual yield (+42.2%) and theoretical yield (+43.1%), effective panicle number and grain number per panicle increased by 33.2% and 13.5%, respectively, while the seed setting rate and 1000-grain weight decreased by 4.2% and 1.6%, respectively. There were significant differences in rice yield and its components under different N rates and N operations. The actual and theoretical yield of rice increased significantly at the N rate of 150－200 kg/hm2, while the effective panicle number and grain number per panicle increased most at the N rate of 250－300 kg/hm2. In addition, with the increase of N rates, the seed setting rate and 1000-grain weight decreased significantly. When the ratio of basal fertilizer+tillering fertilizer to the total nitrogen application was 30%－50% and the N ratio of panicle fertilizer was 10%－30%, the rice yield peaked, while increasing the ratio of basal fertilizer+tillering fertilizer (≤70%) can significantly increase effective panicle number, but reduce grain number per panicle and seed setting rate. And, increasing the ratio of topdressing for panicle initiation (≤30%) can increase grain number per panicle and seed setting rate. For different rice growing regions, there were significant differences for rice yield and its components. The main performance is that the yield increase in the single-season rice from Northeast China is the largest, followed by the single-season and double-season rice in the Yangtze River basin, and the single-season and double-season rice region in South China and the single-season rice in the Yunnan-Guizhou and Sichuan-Hunan Plateau are the smallest. All rice regions achieved high yield by increasing the number of effective panicles and grain number per panicle. The increase of actual and theoretical yield of rice was less affected by SOM(soil organic matter), and the difference between the increase of each SOM level was not more than 4.39% and 2.26%, while the changes of soil TN(total nitrogen), AN(available nitrogen), AP(available phosphorus), AK(available potassium) contents had a greater impact, but there was no significant difference between subgroups. 【Conclusion】 The recommended N rate should not exceed 250 kg/hm2, and the recommended ratio of base fertilizer +tillering fertilizer should not exceed 70% of the total N rate. When the ratio of panicle fertilizer is 10%－30%, it is more beneficial to increase rice yield. Under the condition of ensuring the effective panicles and grain number per panicle of rice, improving the seed setting rate is the key to increase yield in all the rice planting regions in China, which needs comprehensive management measures such as chemical regulation, cultivation density and excellent varieties.

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Effects of Piriformospora indica on the Growth and Antioxidant System of Rice Seedlings Under Salt Stress XIA Yang, LI Chuanming, LIU Qin, HAN Guangjie, XU Bin, HUANG Lixin, QI Jianhang, LU Yurong, XU Jian 2023, 37(5): 543-552.  DOI: 10.16819/j.1001-7216.2023.230201 Abstract ( )   HTML ( )   PDF (1466KB) ( )   【Objective】 This study aims to investigate the impact of Piriformospora indica PI-020 on rice seedling growth, antioxidant-related enzyme activities and gene expression levels in response to salt stress. 【Method】 Different concentrations of PI-020 mycelial suspensions were used to inoculate Nanjing 9108 hydroponic seedlings. The colonization ability of PI-020 in rice seedling roots was evaluated using a microscopy and qPCR. The malondialdehyde (MDA) content of rice leaves was determined, and changes of phenotypic parameters, photosynthetic pigment contents, antioxidant-related enzyme activities and gene expression levels in rice seedlings were analyzed. 【Result】 Under salt stress (100 mmol/L NaCl), PI-020 colonization significantly reduced the MDA content in rice leaves compared to the control. The 200-fold mycelial dilution was the most effective, resulting in a 67.2% decrease in MDA content. After PI-020 colonization, the plant height, root length, leaf area, fresh weight, and dry weight of rice seedlings significantly increased by 34.67%, 23.62%, 58.04%, 59.53%, and 67.25%, respectively, compared to the control. Additionally, PI-020 colonization significantly increased the photosynthetic pigment contents, CAT, APX, POD activities, and the expression levels of antioxidant-related genes OsCAT, OsAPX2, and OsSOD in leaves. 【Conclusion】 P. indica PI-020 reduces the oxidative damage caused by salt stress through improving the antioxidant capacity of rice seedlings, thereby reducing the content of MDA, while alleviating the degradation of photosynthetic pigments, protecting the photosynthetic system. Consequently, it improves the salt tolerance of rice.