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10 July 2021, Volume 35 Issue 4 Previous Issue    Next Issue
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Research Progress and Prospect of Functional Rice Shikai HU, Peisong HU 2021, 35(4): 311-325.  DOI: 10.16819/j.1001-7216.2021.201106 Abstract ( )   HTML ( )   PDF (1108KB) ( )   In this review, we introduced the structure and nutrient compositions of brown rice, and the concept and the connotation of times of functional rice in the new historical period. We emphatically described the types and regulatory mechanisms of bioactive ingredients in functional rice, and summarized the advances in functional rice research by conventional breeding, mutation breeding and genetic engineering. Finally, we summarized the existing problems in the research of functional rice, and forecasted the future development trend of functional rice by taking into consideration the challenges in this front, the current research status, and the public demands for functional rice and its products.

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Towards Understanding the Genetic Regulations of Endosperm Development in Rice Juan ZHANG, Baixiao NIU, Zhiguo E, Chen CHEN 2021, 35(4): 326-341.  DOI: 10.16819/j.1001-7216.2021.210307 Abstract ( )   HTML ( )   PDF (11529KB) ( )   Endosperm, a product of double fertilization, is a tissue nourishing the developing embryo. In addition, cereal endosperm is the primary source of calories of humans. Rice endosperm consists more than seventy percent of the seed dry mass, whose development directly determines the yield and quality of rice grains. To date, we have had a profound understanding of the genetic and epigenetic regulations for rice endosperm development. Many of the important genes required for rice endosperm development have been identified. In this review, we summarize the molecular controls of the key events/processes of endosperm development, including the syncytium-cellualrization transition, endosperm cell differentiation and storage compounds accumulation. We mainly focus on the new findings in rice; however, some important findings in Arabidopsis and other cereal crops are also introduced. We also discuss some questions that need to be elucidated in the future for rice endosperm development.

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Factors Affecting Cadmium Accumulation in Rice and Strategies for Minimization Nan JIANG, Xu YAN, Yanbiao ZHOU, Qunfeng ZHOU, Kai WANG, Yuanzhu YANG 2021, 35(4): 342-351.  DOI: 10.16819/j.1001-7216.2021.200913 Abstract ( )   HTML ( )   PDF (6696KB) ( )   Cadmium (Cd) is an extremely toxic and widely distributed heavy metal. Cd in farmland has adverse impacts on crop growth and development, and threatens human health via the food chain. Rice, as a staple food crop in China, plays an important role in food security. However, rice tends to absorb and accumulate more Cd compared with other cereal crops. The ‘Cd-polluted rice’ events were frequently reported in recent years, which has made Cd pollution a serious public concern. Reducing the Cd accumulation in rice grains is urgent. In this review, we summarize the advances in screening and breeding for rice varieties with low Cd, water management, adjustment of soil pH and foliar dressing strategies. The article aims to lay a theoretical foundation for technological integration, extension and application, and development of new technologies.

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Identification and Gene Mapping of a Lesion Mimic Mutant lm8015-2 in Rice Chen WANG, Beifang WANG, Yingxin ZHANG, Yongrun CAO, Yue ZHANG, Min JIANG, Kangji BIAN, Xiaohui ZHANG, Qunen LIU 2021, 35(4): 352-358.  DOI: 10.16819/j.1001-7216.2021.200908 Abstract ( )   HTML ( )   PDF (26434KB) ( )   【Objective】 To substantiate the genetic mechanisms behind the disease resistance of rice, we identified a rice lesion mimic mutant lm8015-2. 【Method】 lm8015-2 was obtained from an EMS-induced Zhonghui 8015 (ZH8015) mutant library. The SOD, CAT, POD activities, H2O2, MDA, SP, photosynthetic pigments contents, the expression level of defense genes were analyzed in lm8015-2 and its wild-type leaves. The population derived from 02428/ lm8015-2 was used for genetic analysis and fine mapping. 【Result】 Its red rust-like spots were first observed on the tips of the mutant leaves three weeks after sowing, then spread gradually to the whole leaf and throughout the plant at tillering stage, causing the death of whole leaf at heading stage. The shading assay showed that the lesions on the leaves of lm8015-2 were induced by natural light. Meanwhile, photosynthetic pigment contents of lm8015-2 decreased significantly. The staining experiments of EB and DAB showed the excessive H2O2 deposition and cell death of lm8015-2. Compared with the wild type, the activities of SOD and POD, the MDA content increased, while the content of SP decreased in the mutant lm8015-2. Genetic analysis suggested that the phenotype of lm8015-2 was controlled by a single nuclear recessive gene, which was located in a 104 kb interval between the markers W32-85 and C32-8 on chromosome 5. Sequencing analysis revealed that a single base substitution (T to A) of the initiation codon (ATG) occurred in the DNA sequence of LOC_Os05g48390, resulting in the absence of initiation codon. The qRT-PCR results showed the expression of partial defense genes were up-regulated obviously in lm8015-2. 【Conclusion】 The results reveal the target gene is allelic to LTN1, and the mutation of LM8015-2 likely enhances the expression of partial defense genes.

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QTL Analysis for Grain Weight and Shape and Validation of qTGW1.2/qGL1.2 Chengxing DU, Huali ZHANG, Dongqing DAI, Mingyue WU, Minmin LIANG, Junyu CHEN, Liangyong MA 2021, 35(4): 359-372.  DOI: 10.16819/j.1001-7216.2021.201205 Abstract ( )   HTML ( )   PDF (74206KB) ( )   【Objective】 Grain weight and shape have an important impact on the yield and quality of rice. The purpose is to further reveal the genetic mechanism of grain weight and shape in rice by primary mapping of QTLs for grain weight and shape and validating of the newly identified qTGW1.2/qGL1.2 on the long arm of chromosome 1. 【Method】 An F2:3 population consisting of 277 individuals and a recombinant inbred line (RIL) population with 211 individuals were derived from the cross between the large-grain male parent FM9, and the small-grain female parent EFT. The 1000-grain weight (TGW), grain length (GL) and grain width (GW) were measured. QTL mapping was performed by the inclusive composite interval mapping. As for the qTGW1.2/qGL1.2 region, two residual heterozygotes were screened and self-fertilized to produce segregated populations for QTL validation. 【Results】 A total of 35 QTLs for TGW, GL and GW were detected by QTL primary mapping. Among them, 11 QTLs were detected in both populations, 18 QTLs were detected only in the F2:3 population, and six QTLs only in the RIL population. The effects of the newly identified qTGW1.2/qGL1.2 on TGW and GL were validated by using the segregated populations derived from the two residual heterozygotes. Additionally, significant variations in the length of glume cells were observed, and qPCR results demonstrated that the expression levels of genes related to cell cycle, auxin metabolism and grain shape were up- or down-regulated significantly. 【Conclusion】 The primary mapping of 35 QTLs and the validating of qTGW1.2/qGL1.2 will contribute to a deep insight into the genetic basis underlying grain weight and shape of rice, and also lay a foundation for gene cloning and marker assisted selection.

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Effect of Location and Sowing Date on Eating Quality of Semi-waxy japonica Rice Cailin WANG, Yadong ZHANG, Tao CHEN, Zhen ZHU, Qingyong ZHAO, Chunfang ZHAO, Shu YAO, Lihui ZHOU, Ling ZHAO, Xiaodong Wei, Kai LU, Wenhua LIANG 2021, 35(4): 373-382.  DOI: 10.16819/j.1001-7216.2021.210207 Abstract ( )   HTML ( )   PDF (466KB) ( )   【Objective】 The aim of this study is to make clear the eating and cooking quality (ECQ) characteristics of new semi-waxy japonica rice and the influence of environmental conditions during maturity. 【Method】 The starch physical and chemical indexes, rapid visco analyzer (RVA) profile characteristics and ECQs of the tested lines were analyzed by varietal comparative experiments in two sites on two sowing dates. Good taste quality rice varieties Nanjing 46 and Nanjing 9108, which were widely planted, and 38 semi-glutinous japonica rice lines derived from the progenies of the hybrid between Nanjing 46 and Nanjing 9108 were used as materials. 【Result】 The differences of 12 ECQs among 40 semi-waxy japonica rice varieties (lines) were significant at 1% level. The tested lines showed better appearance quality (AQ) and ECQ, the taste value (TV) of 10 lines was higher than that of Nanjing 9108, and the TV of six lines was higher than that of Nanjing 46. The TV of late japonica lines was higher than that of medium japonica lines. In addition to peak viscosity (PKV), the effects of location on the ECQs were significant at 1% level. The most affected characters were TV, consistency viscosity (CSV) and amylose content (AC), followed by AQ, the peak time (PeT) and cool paste viscosity (CPV), with PKV, gel consistency (GC) and breakdown viscosity (BDV) being the least affected. The interaction between sites and varieties for AC, GC, PeT, BDV, setback viscosity (SBV), CSV, AQ and TV were also significant at 5% or 1% levels. Compared with the varieties planted in Nanjing, the AC of the varieties planted in Sihong increased generally, while GC generally decreased. The RVA profile characteristics followed an upward trend except BDV. AQ in Sihong was generally better than Nanjing, TV in Sihong was generally better, with an average increase of 7.8 points. The effects of sowing date on ECQs were significant at 1% level except GT, BDV and SBV. GC was the most affected character, followed by AC, CSV, TV and PeT, and BDV was the least. The interaction between sowing dates and varieties in GC, PKV, HPV, CPV, BDV, SBV and TV was also significant at 5% or 1% levels. When sowing was delayed, AC, PKV, HPV, CPV, PeT, CSV, AQ and TV generally increased, GC decreased, GT, BDV and SBV changed little. 【Conclusion】 The AQ and ECQ of semi glutinous japonica rice were significantly affected by location, sowing date and their interaction with varieties. In the production of high quality rice, it is necessary to select the type of high quality varieties suitable for the local climate conditions, and ensure them of optimum climate and cultivation conditions for grain filling.

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Nitrogen Fertilizer Management for Main Crop Rice and Its Carrying-over Effect on Rhizosphere Function and Yield of Ratoon Rice Jinwen HUANG, Jiayi WU, Hongfei CHEN, Zhixing ZHANG, Changxun FANG, Caihong SHAO, Weiwei LIN, Peiying WENG, Wenxiong LIN 2021, 35(4): 383-395.  DOI: 10.16819/j.1001-7216.2021.200603 Abstract ( )   HTML ( )   PDF (20941KB) ( )   【Objective】 Ratoon rice is the continuation of the main crop. We attempt to elucidate the effect of mechanical transplanting of main crop together with nitrogen fertilizer management on the yield of the main crop and ratoon rice from the perspective of rhizosphere microecosystem, which may provide a reference for the high-yielding and efficient cultivation of ratoon rice. 【Method】 The rice genotype of Yongyou 1540 was used as the material. At a total nitrogen application level of 225.00 kg/hm2 in the main crop, different nitrogen fertilizer treatments were designed to analyze the effects of mechanical cultivation on the yield, root bleeding intensity, enzyme activities and microbial diversity in rhizosphere soil in two consecutive years in paddy field. 【Result】 In N1 and N2 treatments, the root system maintained higher vigor, especially in the late growing period of the main season in the N1 treatment (basal fertilizer : primary fertilizer for tillering : secondary fertilizer for tillering : fertilizer for panicle initiation= 3 : 1 : 2 : 4) showed a significant increase in root bleeding intensity as compared with the control N0 and the local conventional treatment of N4. The total yield of the N1 treatment was the highest in the two growing seasons, reaching an average of 17 351.23 kg/hm2, 23.00% higher than that of N4. Soil enzyme activity analysis showed that the activities of sucrase followed the trend of N2>N1>N3>N4>N0 in the full heading stage during the main season, but N1>N2> N3>N3>N4>N0 for ratoon rice; the activities of catalase and nitrate reductase both followed a trend of N1>N2> N3>N4>N0 in the full heading stage during the main season; the activities of urease, N1>N2> N3>N4>N0 from the heading stage of the main crop to the heading stage of ratoon rice. Highly significant positive correlations were observed between soil enzyme activities and root bleeding intensity at all growing stages. Bacterial 16S rDNA sequencing showed that the structural diversity of bacterial communities differed significantly between the fertilized and non-fertilized treatments, and the Chao1 index and Shannon index of N1 treatment were significantly higher than those of other treatments. Function analysis of rhizospheric bacterial community showed that fertilization increased the number of bacteria closely related to soil carbon and nitrogen cycle, soil organic matter content and soil stress resistance, especially the N1 and N2 treatment with higher relative abundance of nitrospira, which were favorable to soil nitrogen cycle. 【Conclusion】 Under mechanical cultivation, the treatment with properly postponed nitrogen fertilizer application in the main crop is beneficial to the improvement of the rhizosphere microecosystem of ratoon rice, thus improving root vigor, promoting rice growth, and obtaining high yield of rice in both growing seasons.

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Differences in Response to Low Phosphorus Stress Among indica Rice Varieties and Their Agronomic and Physiological Characteristics Shengfeng QIAO, Yaping DENG, Hanbing QU, Weiyang ZHANG, Junfei GU, Hao ZHANG, Lijun LIU, Zhiqin WANG, Jianchang YANG 2021, 35(4): 396-406.  DOI: 10.16819/j.1001-7216.2021.210304 Abstract ( )   HTML ( )   PDF (22497KB) ( )   【Objective】 The purpose of this study is to explore the differences in response to low phosphorus stress among indica rice varieties and their agronomic and physiological characteristics. 【Method】 Twelve medium-maturity indica rice varieties applied in production in Jiangsu Province in the last 80 years were used and two levels of phosphorus concentrations, low phosphorus level (1/20 of the phosphorus concentration of the standard nutrient solution formulation, LP) and the normal phosphorus concentration (International Rice Research Institute standard nutrient solution formulation, control, NP), were designed. 【Result】 The low phosphorus tolerance index was chosen to evaluate the tolerance to low phosphorus (LP) for rice varieties, and the tested cultivars were classified into three categories based on the index: strong tolerance to LP (LP tolerance index ≥0.9), medium resistance to LP (0.5< LP tolerance index <0.9) and weak tolerance to LP (LP tolerance index ≤0.5). Two varieties with strong tolerance to low phosphorus and two with weak tolerance were chosen to investigate the agronomic and physiological characteristics. Plants grown at LP produced significantly lower grain yield than those grown at NP. Compared to NP, LP increased phosphorus translocation efficiency (PTE), internal phosphorus efficiency (IPE) and phosphorus harvest index (PHI). Under the LP condition, PTE and IPE were higher for the varieties with strong tolerance to low phosphorus than for the varieties with weak tolerance to low phosphorus. Compared to the varieties with weak tolerance to low phosphorus, the varieties with strong tolerance to low phosphorus had greater shoot and root biomass, NSC accumulation and remobilization in stem and sheath, less reduction in root oxidation activity, higher increase in acid phosphatase activity in root, more tillers, greater leaf area index and leaf photosynthetic rate at booting stage and grain filling stage. 【Conclusion】 Compared to the varieties with weak tolerance to low phosphorus, larger dry matter accumulation, NSC accumulation and remobilization, root oxidation activity, acid phosphatase activity, leaf photosynthesis rate, and phosphorus utilization efficiency were important agronomic and physiological traits for the varieties with strong tolerance to low phosphorus under LP level.

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A New Approach for Fine-mapping and Map-based Cloning of Minor-Effect QTL in Rice Yujun ZHU, Ziwei ZUO, Zhenhua ZHANG, Yeyang FAN 2021, 35(4): 407-414.  DOI: 10.16819/j.1001-7216.2021.201206 Abstract ( )   HTML ( )   PDF (418KB) ( )   Important agronomic traits in rice are generally controlled by a few major-effect QTLs and a large number of minor-effect QTLs. Great progresses have been made in the cloning of major QTLs, while minor QTLs remain difficult to be cloned due to their small genetic effects and the influence of measurement error. A new approach for fine-mapping and map-based cloning of rice minor-effect QTL was introduced in this article. The approach includes two steps: 1) Use the residual heterozygote to construct near isogenic lines for fine-mapping of the target QTL; 2) Use the genome editing to create mutants of candidate genes for gene function identification. Using the strategy, we fine-mapped six minor QTLs for grain weight and grain size on the long arm of chromosome 1, and successfully cloned the first minor QTL for grain weight. We expect that this approach could provide more options for QTL cloning and new germplasm creation.