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10 November 2019, Volume 33 Issue 6 Previous Issue    Next Issue
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Research Progress on Rice Shattering Yajun GOU, Weifeng YANG, Shaojun LIN, Yanhao GAO, Xin LUAN 2019, 33(6): 479-488.  DOI: 10.16819/j.1001-7216.2019.9038 Abstract ( )   HTML ( )   PDF (1036KB) ( )   Seed shattering is one of the most important traits in wild rice. As an adaptation to the natural environment and the propagation of their offspring, the loss of seed shattering in rice has been a main target during plant selection and domestication. The seed shattering has a direct impact on the yield of rice and the way of its mechanical harvest. The review covers the current advances that have substantially deepen our understanding on seed shattering, such as the physiologic basis responsible for the seed shattering, the identification of crucial genes controlling this trait and the genetic mechanism underlying seed shattering in rice.

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Recent Progress in Molecular Mechanism of Rice Blast Resistance Ni CAO, Yuan CHEN, Zhijuan JI, Yuxiang ZENG, Changdeng YANG, Yan LIANG 2019, 33(6): 489-498.  DOI: 10.16819/j.1001-7216.2019.8126 Abstract ( )   HTML ( )   PDF (414KB) ( )   Rice blast disease, caused by Magnaporthe oryzae, threatens global food security. Owning to the rapid evolution of M. oryzae isolates, resistant cultivars always become susceptible in 3-5 years. Breeding and planting durable resistant cultivars is the most effective method. Recent advances in understanding the pathogenesis of M. oryzae and rice resistance mechanisms led to a deeper understanding of PAMPs- and effector- triggered immunity in this pathosystem. This review summarizes the recent progresses for PTI, the cloned rice blast R genes, cloned Avr genes of M. oryzae and the interaction between them. We also discussed some of the major unanswered questions for this pathosystem and the opportunities for future investigations.

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Phenotypic Analysis and Gene Cloning of Rice Floury Endosperm Mutant fse4 DU Yimo, PAN Tian, TIAN Yunlu, LIU Shijia, LIU Xi, JIANG Ling, ZHANG Wenwei, WANG Yihua*,WAN Jianmin 2019, 33(6): 499-512.  DOI: 10.16819/j.1001-7216.2019. 9058 Abstract ( )   HTML ( )   PDF (3869KB) ( )   【Objective】Starch is the main energy reserve of rice endosperm. The biosynthesis of starch is complex, requiring a large number of synthetic enzymes and regulators. Screening rice endosperm defective mutants and cloning the underlying genes will lay theoretical basis for starch biosynthesis and its regulation. 【Method】 A stable genetic floury and shrunken endosperm mutant termed as fse4 (floury and shrunken4) were obtained from the mutant library of Ningjing 3 (WT), which was induced by N-methyl-N-nitrosourea (MNU). An F2 mapping population was generated by crossing the fse4 mutant with Dular (an indica rice variety) and the gene was finally isolated. The floury seeds segregated from the fse4 heterozygous plants were used to observe the morphological features, and the physicochemical properties of the brown rice flour were analyzed. The endosperm structure was observed with a scanning electron microscopy by the semi-thin section technology. The expression of starch synthesis related genes during grain filling was determined by qRT-PCR; Immunoblotting was used to detect the accumulation of proteins related to starch synthesis. The amino acids contents of each mature endosperm were determined with the fully automatic amino acid analyzer.【Result】The 1000-grain weight and grain size were significantly reduced in fse4. Compared with WT, the contents of total starch, amylose and total protein were signi?cantly lower in fse4, while the lipid content was signi?cantly higher. The starch viscosity, breakdown viscosity and setback viscosity of the fse4 mutant were lower than WT. The endosperm of the mutant had many single dispersed starch granules with large spaces between each other. Using 1568 recessive individuals, FSE4 was narrowed down to a 252 kb region. Sequencing revealed a single base substitution in the first exon of the delta 1-pyrroline-5-carboxylate synthetase (P5CS), resulting in a conserved amino acid variation. Most of the genes related to starch synthesis were downregulated in fse4 and the protein accumulation related to starch synthase were reduced. The contents of various amino acids in fse4 rice flour were increased or decreased, the total free amino acids contents in fse4 seeds was 2.6 times higher than those in WT. Exogenous proline was applied during the germination of fse4 seeds, and the embryonic lethal phenotype was partially recovered.【Conclusion】FSE4 encode the key rate-limiting enzyme P5CS of proline synthesis, which plays an important role in the biosynthesis and metabolism of amino acids in endosperm and affects the accumulation of starch.

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Grain Quality as Affected by Down-regulation of Expression of Different ALK Alleles in indica Rice (Oryza sativa L.) Zhuanzhuan CHEN, Xianfeng LI, Min ZHONG, Jiaqi GE, Xiaolei FAN, Changquan ZHANG, Qiaoquan LIU 2019, 33(6): 513-522.  DOI: 10.16819/j.1001-7216.2019. 9090 Abstract ( )   HTML ( )   PDF (1854KB) ( )   【Objective】 Gelatinization temperature (GT) is one of the key physicochemical properties in rice quality, which is mainly regulated by ALK (SSII-3) gene. In general, there are two ALK alleles among indica cultivars. To detect their functional differentiation in indica rice,【Method】 Zhenshan 97B (a high GT variety carrying ALKc allele) and Longtefu B (a low GT variety carrying ALKb allele), were used as receptors for the generation of transgenic rice with down-regulation of ALK expression by RNA interference (RNAi).【Result】 Down-regulation of ALK gene significantly decreased the GT of the transgenic lines. Due to the difference of original GT between the two receptors, the GT of transgenic rice lines derived from Zhenshan 97B (a high GT variety) decreased significantly, but it is slightly decreased in transgenic plants derived from Longtefu B (a low GT variety). The differential scanning calorimetry (DSC) results showed that the initial temperature of RNAi transgenic rice was significantly lower than the corresponding control and the transgenic lines were gelatinized in advance. The peak value of GT(Tp) in RNAi rice grains was significantly lower than that of the control under Zhenshan 97B background. However, Tp of RNAi rice grains under Longtefu B background was significantly lower than the control to a lesser extent. Also, down-regulation of ALK expression had a significant effect on rice physical-chemical characteristics. An increase of apparent amylose content in RNAi transgenic plants was detected due to the decreased expression of ALK gene. Besides, the pasting properties showed that down-regulation of ALK gene had obvious effects on peak viscosity and breakdown value, improving the taste of the transgenic rice. The gel consistency was significantly different among Zhenshan 97B RNAi lines and their parents, but no difference was found in Longtefu-derived transgenic lines.【Conclusion】 RNA interference to ALK allele expression had a significant effect on rice quality, especially the gelatinization characters. Down-regulated expression level of ALKc allele would cause larger variation of physical-chemical characteristics between transgenic rice and their parent than that of ALKb allele.

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Analysis on Chinese Improved Rice Varieties in Recent Four Decades Zhiguo E, Benyi CHENG, Hongwei SUN, Yujun WANG, Lianfeng ZHU, Hai LIN, Lei WANG, Hanhua TONG, Hongqi CHEN 2019, 33(6): 523-531.  DOI: 10.16819/j.1001-7216.2019.9084 Abstract ( )   HTML ( )   PDF (1631KB) ( )   【Objective】 Summarizing the breeding experience of predecessors in time and mastering the genealogies of the improved varieties will not only help understand the breeding history, but also provide breeders with an extremely important reference in parent screening, which can make breeding more targeted.【Method】 Based on the ASP. NET and VB. net, the program algorithm is compiled to analyze the variety data, and the relevant results are presented in R language.【Result】 From 1979 to 2018, 9563 rice varieties were approved by national or provincial approval authorities 4159 of which were widely applied. Most of the backbone parents of indica rice are maintainer and restorer lines of hybrid combinations, but the use of hybrids also reduces the diversity of parents.【Conclusion】 Over the past 40 years, rice breeding in China has made great strides, and bred varieties have emerged in endlessly. The yield per unit area of rice varieties has been increased as well as the edibility quality and the resistance to blast and bacterial blight improved.

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Physiological and Molecular Mechanisms of Hydrogen Sulfide Enhancing Phosphorus Absorption and Transportation in Rice Chunquan ZHU, Xiaochuang CAO, Lianfeng ZHU, Zhigang BAI, Jie HUANG, Qingduo LIANG, Qianyu JIN, Junhua ZHANG 2019, 33(6): 532-540.  DOI: 10.16819/j.1001-7216.2019.9055 Abstract ( )   HTML ( )   PDF (1766KB) ( )   【Objective】 Low phosphorus (P) stress is one of the main factors limiting rice yield. Hydrogen sulfide (H2S) is produced in rice under flooding conditions. However, whether H2S is involved in the regulation of rice response to phosphorus deficiency stress as a signal molecule is still unclear. 【Method】 The content of H2S in rice was determined under normal and low P conditions to illuminate the role that H2S plays in regulating rice response to P deficiency stress. Rice was pretreated with 2 μmol/L H2S precursor NaHS for 1 day, then cultured for another 6 days under P sufficient and deficient conditions. The total P contents, acid phosphatase activity, antioxidant enzyme activity, xylem P concentration, P transporter genes’ expression and rice root architecture were determined to explore the physiological and molecular mechanism of H2S in regulating rice response to phosphorus deficiency stress. 【Conclusion】 Low P stress significantly increased the content of H2S in rice roots and shoots. NaHS pretreatment significantly increased total P contents, root acid phosphatase activity, root antioxidant enzymes activity, xylem P concentration and stimulated the expression of P transporter genes. Meanwhile, NaHS pretreatment modified rice root architecture, including increased total root length, total root surface area, total root volume and total root tip numbers. Therefore, our present study demonstrated that H2S improved P absorption and translocation in rice under P deficiency conditions and finally alleviate P deficiency stress in rice.

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Relationship of Grain Protein Content with Cooking and Eating Quality as Affected by Nitrogen Fertilizer at Late Growth Stage for Different Types of Rice Varieties Lü SHI, Xinyue ZHANG, Huiyan SUN, Xianmei CAO, Jian LIU, Zujian ZHANG 2019, 33(6): 541-552.  DOI: 10.16819/j.1001-7216.2019.9022 Abstract ( )   HTML ( )   PDF (657KB) ( )   【Objective】 The aim of this study is to clarify the relationship of grain protein content with cooking and eating quality in different types of rice varieties and effects of nitrogen fertilizer at late growing stage. 【Method】 Different nitrogen fertilizer levels were applied at heading stage to analyze the relationship between protein and its components contents and cooking and eating quality by using three conventional indica rice varieties and three conventional japonica rice varieties.【Result】 Regardless of indica or japonica, nitrogen fertilizer application at late growth stage significantly increased the protein content of rice, and the response to nitrogen fertilizer significantly varied with varieties, with nitrogen fertilizer exerting much greater effects than varieties. The four components contents all increased significantly with rising nitrogen fertilizer level at late growing stage, and gliadin and glutenin contants showed a greater response to nitrogen fertilizer application. With increasing nitrogen fertilizer level, the amylose content decreased and gel consistency was significantly shorter, the peak viscosity, hot viscosity, breakdown and final viscosity of the starch gelatinization characteristic values followed a downward trend, while the consistence and setback showed a upward trend and the taste value decreased significantly. Correlation analysis showed that the total protein content had an extreme significant negative correlation with gel consistency in indica and japonica rice. The protein content of indica rice also had an extreme significant negative association with the taste value (r=-0.975**) and peak viscosity, but was negatively associated with the breakdown, and positively or significantly positively interrelated with the consistence and setback. The protein content of japonica rice was negatively correlated with the taste value (r=-0.923**) and breakdown at extremely significant level, and was significantly negatively correlated with the peak viscosity, and the relationship with the consistence and setback was basically the same as that of indica rice. The taste value of indica rice and japonica rice were all negatively related to globulin, gliadin and glutenin contents at extremely significant level, and albumin accounted for the smallest proportion, which was negatively correlated with the taste value at extremely significant level for indica rice, while had no significant correlation in japonica rice.【Conclusion】 The rising nitrogen fertilizer level at late growing stage significantly increased the protein and its components contents of rice. The increasement of protein content significantly degraded the cooking quality and palatability of rice. At the same time, the augment of four protein components would also deteriorated the taste of rice to varying degrees, especially for globulin and gliadin, the negative effect of glutenin could not be ignored especially in indica varieties.

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Status, Problems and Solutions in Rice Industry Development in the Middle Reaches of the Yangtze River Zhenghong ZHAO, Li DAI, Jianliang HUANG, Xiaohua PAN, Aiqing YOU, Quanzhi ZHAO, Guanghui CHEN, Zheng ZHOU, Wenbin HU, Long JI 2019, 33(6): 553-564.  DOI: 10.16819/j.1001-7216.2019.9061 Abstract ( )   HTML ( )   PDF (490KB) ( )   The survey was conducted by the rice researchers from Hunan, Hubei, Jiangxi and Henan provinces, aiming to learn the development situation of rice industry in the middle reaches of the Yangtze River after the rice protection purchase price was lowered. The results showed that: mainly due to the adjustment of paddy field planting mix and the change from double cropping to single-cropping in Hunan and Jiangxi provinces, the total rice planting area in 2018 and 2019 years was expected to decline, while the area of Hubei and Henan provinces were raised slightly. In 2018, the sales fell well behind the schedule as compared with 2017. And the rice sales price also reduced. They were mainly affected by the downward adjustment of the national rice protection price. However, the sales schedule and price of high-quality rice were less influenced, and its circulation was more market-oriented. In 2018, the labor, land, fertilizer and total costs of rice planting all increased to varying degrees, and the land rent and labor cost increases were the main reason. Also, the rice purchase volume and price, and rice wholesale price of rice processing enterprises declined in 2018. In this region, high-quality rice and hybrid rice accounted for 64% in planting area, and the indica rice for 97.6%. And the ratios of rice production patterns in the area are as follows: broadcasting>artificial transplanting and direct seeding>mechanical transplanting; While, the growing area of ratoon rice is increasing, and the pattern of rice-fishing culture has seen a rapid growth. At the same time, a series of problems is hindering the development of the industry, such as the wide spread decline of farmers’ enthusiasm in growing grain rice, rising risk in contract farming development, the imperfect agricultural infrastructure and unclear division accountable for the renovation, incomplete market-based agricultural production, the hidden dangers of the disorderly development of rice-fishing mode, the difficult, costly and risky grain selling of farmers, and the less regional rice brand, and so on. At last, the advice to the government was proposed.

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Protective Effect of Glutaredoxin (AbGrx-1) on Aphelenchoides besseyi Under Oxidative Stress Hui FENG, Yalei FAN, Jinfeng ZHANG, Hongli ZHU, Lihui WEI 2019, 33(6): 565-574.  DOI: 10.16819/j.1001-7216.2019.9016 Abstract ( )   HTML ( )   PDF (1902KB) ( )   【Objective】 The antioxidant glutaredoxin (Grx) plays a crucial role in regulating intracellular redox homeostasis via scavenging of excess reactive oxygen species. The white-tip nematode Aphelenchoides besseyi can survive in adverse environments including high temperature, osmosis and oxidative stresses. To reveal the antioxidant function of Grx in A. besseyi, 【Method】 herein the full-length cDNA of glutaredoxin (named AbGrx-1) from A. besseyi was cloned by using rapid amplification of cDNA ends (RACE), and AbGrx-1 protein and evolutionary relationship were characterized; differential gene expression level was detected in the nematodes under oxidant and temperature stresses by using quantitative real-time PCR; the effect of the recombinant AbGrx-1 protein on A.besseyi survival was also tested.【Result】 The full-length AbGrx-1 cDNA contains a 5' UTR of 90, an ORF of 321 bp encoding a polypeptide of 106 amino acids and a 3' UTR of 97 bp. The deduced amino acid sequence of AbGrx-1 shares a high similarity with other nematodes’ Grxs, and the catalytic residue (CPYC) and glutathione binding sites (RSVP and GGDD) indicate that AbGrx-1 is categorized into Class I Grx. The phylogenetic tree showed AbGrx-1 is located in the same clade with the plant parasitic nematode Aphelenchus avenae. AbGrx-1 mRNA is highly induced in A. besseyi exposed to H2O2 solution and 12℃, but is suppressed in the nematodes at 0, 4, 37 and 45℃. The high concentration H2O2 solutions and high temperature are adverse to survival of A. besseyi, but the survival rate increases with the nematodes pre-soaked in AbGrx-1 recombinant protein solution. 【Conclusion】 AbGrx-1 is required for A. besseyi antioxidative immunity, and plays an essential role in overcoming oxidative damage and nematode survival.