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10 January 2018, Volume 32 Issue 1 Previous Issue    Next Issue
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Research Progress on Cloning and Regulation Mechanism of Rice Grain Shape Genes Xi LIU, Changling MOU, Chunlei ZHOU, Zhijun CHENG, Ling JIANG, Jianmin WAN 2018, 32(1): 1-11.  DOI: 10.16819/j.1001-7216.2018.7016 Abstract ( )   HTML ( )   PDF (17562KB) ( )   Grain shape is an important trait that affects the yield and quality of rice, so it is necessary to understand the genetic regulation mechanism of grain shape to improve rice yield and quality. Grain shape is characterized by a combination of grain length, grain width, grain thickness, and grain length-to-width ratio, belonging to quantitative traits, which is controlled by different genetic systems, such as embryo, endosperm and maternal plant. With the rapid development of rice functional genomics and re-sequencing technology, more than 400 QTLs related to rice grain shape have been located at present, and at least 60 genes associated with rice grain traits have been identified. Some rice grain shape regulation pathways were identified, including phytohormones, the ubiquitin-proteasome pathway, the mitogen-activated protein kinase (MAPK) signaling pathway, epigenetic modification, the G protein signaling pathways. In this review, we systematically summarize and sort out the research progress of the cloning and functional analysis of rice grain shape genes, and evaluate the utilization value of rice grain shape genes in rice breeding for high yield and good quality.

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Overexpression of OsENO2-2 Affects Heading Date in Rice Xiaoyun LIU, Xiao LI, Tengfei LI, Lufang SU 2018, 32(1): 12-22.  DOI: 10.16819/j.1001-7216.2018.7055 Abstract ( )   HTML ( )   PDF (42061KB) ( )   【Objective】 OsENO2-2 was isolated from japonica cultivar Zhonghua 11 as a short transcript produced by alternative splicing of OsENO2 which is homologous to AtENO2. To reveal the function of OsENO2-2,【Method】 we constructed an overexpression vector of OsENO2-2 and obtained the transgenetic plants. Based on the observation and statistics of phenotype in overexpressed plant and wild-type, we validated the function of OsENO2-2 using reverse genetics method. 【Result】 Overexpression of OsENO2-2 transgenetic plants delayed heading date only under long-day conditions but not short-day conditions. qRT-PCR expression analysis of the critical flowering time genes showed that in long-day conditions, the expression of RFT1 in overexpressed plants was downregulated, and the expression levels of the other tested genes did not change significantly in wild-type and overexpressed plants; but in short-day conditions, the expression of all the tested genes in wild-type and over-expression plants did not change significantly. 【Conclusion】 OsENO2-2 might be involved in the photoperiodic pathways to regulate the heading date in rice by regulating the expression of RFT1 gene.

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Identifying of QTLs for Resistance to Metal Irons Stress in Rice Han LIN, Jiangmin XU, Huqian HU, An ZHENG, Wanlu XU, Ping LOU, Yuexing WANG, Dali ZENG, Yuchun RAO 2018, 32(1): 23-34.  DOI: 10.16819/j.1001-7216.2018.7075 Abstract ( )   HTML ( )   PDF (48799KB) ( )   【Objective】 The molecular markers linked to the tolerance of various metal ions during rice seeding stage were screened for the purpose of discussing the genetic basis of the resistance to different metal ions.【Method】 A rice double haploid(DH) population, derived from a typical indica-japonica cross(Chunjiang 06/TN1) via the anther culture was used to analyze the resistance of four metal ions(Fe2+, Cd2+, Al3+, Na+) in DH population and its parents, then the quantitative trait loci (QTL) for the resistance of the four metal ions were identified using an available and complete molecular linkage map. In addition, real-time quantitative PCR was used to detect the expression of related genes before and after treatment.【Result】 A total of 8 QTLs for resistance to metal ions stress were detected, which were localized on chromosomes 1, 2, 4, 6, 9, 10 and 11. Among them, one QTL with the greatest contribution for resistance to Fe2+ treatment(24.47%, threshold is 7.78) located in the region RM1297–RM1061 on chromosome 1. Meanwhile, the expression analysis of the genes related to stress tolerance in this interval showed that these genes had different expression levels before and after treatment. One QTL was detected after Cd2+ treatment, which was located on chromosome 1. Five QTLs were detected after Al3+ treatment, which were located on chromosomes 2, 4, 6, 10 and 11 respectively. And one QTL was detected after Na+ treatment, which was located on chromosome 9. 【Conclusion】 According to the QTL analysis of phenotypic differences among DH groups which were treated with different metal ions, eight QTLs for resistance to various metal ions were detected. It laid the foundation for the fine mapping and cloning of the corresponding QTL and exploring the QTL molecular regulation mechanism of the resistance to different metal ions in rice.

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Wx Gene Editing via CRISPR/Cas9 System in Rice Bingkun WANG, Hui ZHANG, Ruke HONG, Jinwen ZHANG, Rui YANG, Qiong LUO, Qianchun ZENG 2018, 32(1): 35-42.  DOI: 10.16819/j.1001-7216.2018.7061 Abstract ( )   HTML ( )   PDF (3092KB) ( )   【Objective】 Amylose content is closely related to rice quality. The objective of this research is to knockout Wx gene for obtaining rice mutants with suitable amylose content.【Method】 Vector pGK03-Wx-gRNA, a CRISPR/Cas9 system, targeted either the first (target 1) or the second (target 2) exon of Wx gene was constructed and transformed into super-rice Chujing 27 to edit the Wx gene. Independent transformants were obtained via Agrobacterium-mediated transformation with hygromycin selection. The transgenic lines of T0, T1 and T2 generations were identified by DNA sequencing, in addition to qPCR and amylose content assay of T1. 【Result】 Nine T0 independent transgenic lines were generated, the L1-L5 from target 1 and L6-L9 from target 2. Eight lines (L1-L8) were mutants and L9 was not confirmed as mutant by sequencing. Therefore, the mutation rate was 100% for target 1, and 75% for target 2. T1 and T2 generations of the eight lines (L1-L8) were further sequenced, which revealed two types of mutation: base deletion (single base, double and up to fourteen bases), and base insertion. Some lines (L1, L2, L3 and L6) were reedited at T1 generation when compared to its T0 generation, while the rest lines were stable at the mutation sites. All the eight mutants were stable when comparing their target gene sequence at T1 and T2 generations. qPCR results indicated that Wx gene expression at RNA level was considerably reduced in the mutant. The seed amylose content was reduced from 17.5% to 1.93%(P<0.01). 【Conclusion】 The Wx gene was successfully edited by CRISPR/Cas9 system in rice, the inheritable mutants with average amylose content at 1.93% were obtained, which would provide valuable germplasm for rice quality improvement.

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QTL Analysis for Mineral Contents in Brown Rice Using a BC2F4:5 Population Derived from Dongxiang Wild Rice (Oryza rufipogon Griff.) Biaolin HU, Derun HUANG, Yeqing XIAO, Qiangsheng HE, Yong WAN, Yeyang FAN 2018, 32(1): 43-50.  DOI: 10.16819/j.1001-7216.2018.7011 Abstract ( )   HTML ( )   PDF (710KB) ( )   【Objective】 Biofortifying food crops with essential minerals would alleviate mineral deficiencies in humans.【Method】 One plant A58 was selected from Xieqingzao B// Xieqingzao B /Dongxiang wild rice BC1F5 population, and was backcrossed with Xieqingzao B to develop a BC2F4:5 population. The contents of Mg, Ca, Zn, Fe, Mn and Cu in brown rice of 132 BC2F4:5 lines were measured with an inductively coupled plasma atomic emission spectrometer (ICP-AES). Detection of quantitative trait loci (QTLs) for mineral contents in brown rice was conducted using Windows QTL Cartographer 2.5.【Result】 A total of 17 QTLs for mineral contents in brown rice were detected on chromosomes 1, 4, 6, 8, 9 and 11, respectively, including one for Mg content, four for Ca content, four for Zn content, two for Fe content, two for Mn content, and four for Cu content. The explained phenotypic variations ranged from 5.0% to 47.2%, and eight QTLs of them had the enhancing alleles derived from Oryza rufipogon. 【Conclusion】 Twelve QTLs were clustered in five chromosomal regions, indicating that common genetic-physiological mechanisms were involved for different mineral nutrients, and the beneficial alleles could be utilized to improve grain nutritional quality by marker-assisted selection.

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Tolerance to Low Phosphorus and Its Agronomic and Physiological Characteristics of Rice Cultivars Yinyin LI, Gengwen XU, Junfeng LI, Jiarong GUO, Zhiqin WANG, Jianchang YANG 2018, 32(1): 51-66.  DOI: 10.16819/j.1001-7216.2018.7047 Abstract ( )   HTML ( )   PDF (1810KB) ( )   【Objective】 The purpose was to elucidate the evaluation index of tolerance to low phosphorus (LP) and agronomic and physiological characteristics of rice cultivars with strong resistance to LP. 【Method】 Eleven typical japonica rice cultivars applied in Jiangsu Province during the last 70 years were used and two levels of phosphorus concentrations, low phosphorus level (1/20 of the phosphorus concentration in the standard nutrient solution formulation, LP) and the normal phosphorus concentration (International Rice Research Institute standard nutrient solution formulation, control), were designed. 【Result】 LP tolerance index (grain yield of LP treatment × LP tolerance coefficient/average grain yield of LP treatment for all tested cultivars) and dry matter index (dry matter of LP treatment/ dry matter of control) were significantly or extremely significantly and positively correlated with the LP tolerance coefficient (grain yield of LP treatment/ grain yield of control) and grain yield under the LP treatment. Therefore,the LP tolerance index and dry matter index were chosen as indexes to evaluate the tolerance to LP for rice cultivars. The tested cultivars were classified into three categories based on the two indexes: strong tolerance to LP (both LP tolerance index and dry matter index >1), medium resistance to LP (both LP tolerance index and dry matter index > 0.6 and either LP tolerance index or dry matter index < 1) and weak tolerance to LP (both LP tolerance index and dry matter index≤0.6). Compared with those with weak tolerance to LP, the cultivars with strong tolerance to LP exhibited higher root dry weight, stronger root activity, more tiller number at the early tillering stage, larger total leaf area index (LAI), high-efficiency LAI, effective LAI and sink capacity, more accumulation of sugars in the stem and sheath at heading time and greater dry matter production capacity from heading to maturity. The LP treatment increased internal phosphorus use efficiency (grain yield/phosphorus uptake of plants) and the phosphorus harvest index (phosphorus in the grain/the total absorbed phosphorus in plants) in comparison with the control. Moreover, the cultivars with strong tolerance to LP showed much higher internal phosphorus use efficiency.【Conclusion】 The LP tolerance index and dry matter index can be used as indexes to evaluate the tolerance to LP for a rice cultivar. Under the LP treatment, higher root dry weight, more tiller number at the early tillering stage, larger sink capacity and greater dry matter production capacity during gain-filling period are the main agronomic and physiological characteristics of rice cultivars with strong tolerance to LP and high phosphorus use efficiency.

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Dry Matter Accumulation and N, P, K Absorption and Utilization in Rice-Ratoon Rice System Sen WANG, Jinghua MO, Yang WANG, Qiuxiang YOU, Tao REN, Rihuan CONG, Xiaokun LI 2018, 32(1): 67-77.  DOI: 10.16819/j.1001-7216.2018.7027 Abstract ( )   HTML ( )   PDF (953KB) ( )   【Objective】 To reveal the law of dry matter accumulation, N, P, K nutrients absorption and utilization in rice-ratoon rice system and lay a theoretical basis for scientific fertilization, 【Method】 two years of field trials were conducted to study the dynamics of dry matter accumulation and N, P, K distribution and transformation in rice-ratoon rice system by investigating the dry matter weight and nutrients contents in different organs at various growth stages(tillering stage, young panicle differentiation stage, booting stage, full heading stage, filling stage, ripening stage) under the condition of adequate supplying of nutrients. 【Result】 Total dry matter accumulation of the first-season rice followed the growth trend of ‘slow-fast-slow’ in the whole growth duration. The rapid accumulation period in stem and leaf were ‘tillering-full heading stage’ and ‘before the booting stage’, respectively, and the accumulation in stem and leaf accounted for 81.1% and 43.8% of their maximum. In addition, the dry matter accumulation in stem and leaf were not decreased significantly during the grain filling stage. The rapid dry matter accumulation period of panicle was from full heading stage to middle filling stage, which accounted for 58.8% of the total. The total dry matter accumulation of ratoon rice followed an S-shape curve. Dry matter accumulation in stem and leaf peaked at the filling stage and heading stage respectively, and that of the first-season rice stubble showed a downward trend in the whole growth period. The results of nutrient absorption showed that total N accumulation of the first-season rice was equal to that of the dry matter accumulation, as well as that of the stem and panicle. But the total accumulation of phosphorus and potassium of the first- season rice were decreased at the late filling stage. Nutrients accumulation of stem and leaf reached the maximum at heading stage. After harvest of the first season rice, accumulation of N, P and K in stubbles showed a downward trend, and that of ratoon rice stem and leaf were increased firstly and then decreased. However, that of panicle were increased constantly. From heading stage to ripening stage, N translocation in each organ showed a tendency of leaf>stem>stubble, for P translocation, stem>stubble>leaf, and for K translocation, stubble>leaf>stem. 【Conclusion】 The rapid dry matter and nutrient accumulation period of the first-season rice was from booting stage to middle filling stage, and the critical period of ratoon rice was from the harvest of the first-season rice to full heading stage. The nutrient in stubbles could be transferred to the organs of ratoon rice after the harvest of the first season rice. Satisfying the nutrients demands between heading stage and filling stage of the first-season rice and timely nutrients supply to ratooning buds served as the basis and guarantee of high yield in rice-ratoon rice system.

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Leaching Method of Available Nitrogen in Rice Potted Soil and Effect Analysis of Short-term Nitrogen Deficiency Hui WU, Jing XIANG, Huizhe CHEN, Yuping ZHANG, Yikai ZHANG, Guangmei JI, Yaliang WANG, Hongzhi SHI, Wenqian ZHANG, Defeng ZHU 2018, 32(1): 78-88.  DOI: 10.16819/j.1001-7216.2018.7069 Abstract ( )   HTML ( )   PDF (1131KB) ( )   【Objective】 This study aims to explore a simple and effective leaching method of available nitrogen in potted soil, and to reveal the effects of soil nitrogen deficiency at different periods before anthesis on nitrogen accumulation in main functional leaves and post-anthesis plant of different types rice, which would clarify the characteristics of nitrogen accumulation and translocation after anthesis, and lay the research foundation for reducing nitrogen fertilizer application. 【Method】 In this study, the effects of three leaching methods on available nitrogen reduction in potted soils were compared. Meanwhile, the effects of short-term nitrogen deficiency 14 d and 3 d before anthesis on SPAD value, nitrogen concentration of top-three leaves and plant nitrogen content after anthesis were discussed using indica-japanica hybirid rice Yongyou 12(YY12), and indica hybrid rice variety Zhongzheyou 1(ZZY1). 【Results】 The results showed that 85.6% nitrate nitrogen and 67.1% ammonium nitrogen in soil could be eluted by leaching structure + sandy /soil mixed matrix(T3) with 3 times of leaching. Under the two leaching treatments, the contents of nitrate and ammonium nitrogen in potted soil decreased by 42.1%-59.3% and 35.0%-43.9%, respectively. This could achieve the expected effect of reducing soil nitrogen to inhibit effectively the soil available nitrogen supply capacity in the short term. Affected by soil nitrogen deficiency before anthesis, SPAD value and nitrogen concentration of top-three leaves, stem-sheath, leaves, panicle and plant nitrogen content at the 10th day after heading of YY12 were decreased significantly. At the same time, there was a remarkable difference of stem-sheath, panicle and plant nitrogen content between the two leaching treatments. SPAD value and nitrogen concentration of top-three leaves, panicle and plant nitrogen content at the 10th day after heading of ZZY1 were also decreased dramatically under the leaching treatment 14 d before anthesis. However, the leaching treatment 3 d before anthesis had little effect on nitrogen concentration of top-three leaves and plant nitrogen content. 【Conclusion】 In conclusion, the sensitivity of rice to nitrogen deficiency 14 d before anthesis(meiosis stage) was greatly higher than that 3 d before anthesis. The sensitivity of leaf color and nitrogen concentration of leaves at different leaf positions to soil nitrogen deficiency were enhanced from bottom to top. The influence of soil nitrogen deficiency at the two leaching periods on YY12 was greater than that of ZZY1, which means that the lower demand for soil available nitrogen of indica hybrid rice ZZY1 after anthesis, and the higher demand of indica-japanica hybirid rice YY12 after the meiosis period.

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Influence of Rice dwarf virus on Biological Parameters and Population Growth of Vector Insect Nephotettix cincticeps (Uhler) (Hemiptera: Cicadellidae) Qianjin WANG, Cong DANG, Qi FANG, Gongyin YE 2018, 32(1): 89-95.  DOI: 10.16819/j.1001-7216.2018.7090 Abstract ( )   HTML ( )   PDF (551KB) ( )   【Objective】 The rice dwarf virus (RDV), a phytoreovirus in the family Reoviridae, is the pathogeny of rice dwarf virus disease. RDV is mainly transmitted by green rice leafhoppers, Nephotettix cincticeps (Uhler) (Hemiptera: Cicadellidae), in a persistent-propagative manner and is transovarially transmitted to offspring and caused great decreases to rice yields. Our aim is to study the effects of RDV on leafhoppers survival, development, reproduction and population growth, and to explore the “double” damage mechanism by RDV and vector green rice leafhoppers and finally to reveal the mechanism within the tritrophic relationship.【Method】 We compared the biological parameters of the green rice leafhoppers on RDV-infected and non-infected rice plants, life table of experimental population of leafhopper was established. We also analyzed the influence of RDV on green rice leafhoppers population growth.【Result】 Compared with healthy rice plants, female nymphal duration was significantly shorter, nymph survival, male adult longevity and fecundity were significantly longer/higher on RDV-infected rice plants. Other biological parameters were not largely affected. Among the five life table parameters, only net reproductive rates (R0) was significantly affected, it was largely higher on RDV-infected rice plants compared with healthy rice plants. The green rice leafhopper population grew faster on RDV-infected rice plants and the total number of adults was significantly higher than healthy rice plants at the 4th, 5th and 6th month after inoculation.【Conclusion】 RDV could enhance survival rate, fecundity and accelerate population growth of green rice leafhoppers.

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Effect of Foliar Application of Na2SeO3 on the Yield and Quality of Ratooning Rice Menjun DUAN, Yucong TIAN, Yunzi WU, Tao JIN, Fu CHEN, Zhangyong LIU 2018, 32(1): 96-102.  DOI: 10.16819/j.1001-7216.2018.7077 1 Abstract ( )   HTML ( )   PDF (390KB) ( )   【Objective】 The objective of this study is to reveal the effects of foliar application of selenium on the yield and quality of ratooning rice, which will lay a theoretical basis for high quality and high yield cultivation of ratooning rice.【Method】 The experiment was carried out at Shakou Town, Honghu City, Hubei Province in 2016 with Fengliangyouxiang1 as the experimental material and Na2SeO3 as selenium source. Foliar spray of Na2SeO3 was conducted in the initial heading stage, full heading stage, and initial heading date+full heading date at 0g/hm2, 5.625g/hm2, and 11.250g/hm2.【Result】 The foliar application of Na2SeO3 increased the yield of ratooning rice with no significant difference between the control and the treatment with Na2SeO3 spraying in initial heading stage. Na2SeO3 spray during the full heading date at 5.625g/hm2 and 11.250g/hm2 increased the rationing rice yield by 2.59% and 5.50%, respectively, foliar spraying of 5.625g/hm2 and 11.250g/hm2 Na2SeO3 duning initial heading date and full heading date increased the yield by 4.83% and 7.08%, respectively. The suitable dosage was 11.250g/hm2 for initial heading date and heading date, with the highest yield of 5533.33kg/hm2. The foliar application of Na2SeO3 increased yield by increasing grain number, filled grain number and seed setting rate. The foliar application of Na2SeO3 can improve the quality of ratooning rice. The suitable dosage was 11.250g/hm2 for full heading date. The spraying of selenium fertilizer improved quality by increasing whole polished rice rate, and reduced the chalky grain rate. At the full heading date, under foliar spraying of 11.250g/hm2 Na2SeO3 the whole polished rice rate was the highest(61.37%) and the chalky grain rate was the lowest (9.37%).【Conclusion】 The results showed that the application of Na2SeO3 could improve the yield and quality of ratooning rice. The yield of ratooning rice peaked during initial heading date and full heading date at 11.250g/hm2 Na2SeO3; ratooning rice had the best quality at 11.250g/hm2 Na2SeO3 in the full heading date.