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    10 September 2020, Volume 34 Issue 5 Previous Issue    Next Issue

    Research Papers
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    Research Papers
    Tryptophanyl-tRNA Synthetase Gene WRS1 Regulates Rice Seed Development
    Xiaohan TANG, Shijia LIU, Xi LIU, Yunlu TIAN, Yunlong WANG, Xuan TENG, Erchao DUAN, Yuanyan ZHANG, Ling JIANG, Wenwei ZHANG, Yihua WANG, Jianmin WAN
    2020, 34(5): 383-396.  DOI: 10.16819/j.1001-7216.2020.0302
    Abstract ( )   HTML ( )   PDF (5539KB) ( )  

    【Objective】 Aminoacyl-tRNA synthetases (aaRSs) are closely related to the transmission of genetic information. Besides translation, aaRSs in plants participate in gametogenesis and embryo development, early plastid development, immune signal perception and disease defense. In this study, we used a rice endosperm defective mutant to analyze the function of tryptophanyl-tRNA synthase (WRS1) during seed development, proving that WRS1 gene encodes a key factor affecting rice endosperm development. 【Method】 In this study, a stably-inherited rice floury endosperm mutant (wrs1) was screened from the mutant library of indica cultivar N22 (Oryza sativa subsp. indica) induced by ethyl methane sulfonate (EMS). Map-based cloning and complementation test identified the target gene. Morphological observation and starch physicochemical properties of wrs1 mature seeds were analyzed. Semi-thin sections were prepared to observe the developing endosperm structure with a scanning electron microscope. qRT-PCR and GUS staining were performed to analyze the expression of WRS1. The expression of starch synthesis related genes in the endosperm at 12 days after flowering was determined by qRT-PCR, and these protein expression levels in mature seed were detected by immunoblotting. The free amino acid contents of mature seeds were measured with a fully automatic amino acid analyzer. 【Result】 The seedlings of wrs1 were featured by obvious delay in development and finally withered and died. The floury grains isolated from the heterozygous mutant (WRS1wrs1) showed shrunken belly, decreased grain thickness and thousand-grain weight. Total starch contents, the peak viscosity and breakdown viscosity of pasting starch were lower in wrs1. The compound starch granules in developing endosperm of wrs1 were smaller and loosely arranged. WRS1 was restricted to the 183 kb region of the long arm of chromosome 12. Sequencing revealed a single base substitution in exon 6 of the tryptophanyl-tRNA synthetase gene (WRS1), resulting in a substitution of methionine. The expression of most starch synthesis-related genes in wrs1 was down-regulated, while these proteins showed different accumulation levels. The contents of proteins in wrs1 grains were decreased, while free amino acids contents were significantly increased. 【Conclusion】 WRS1 encodes tryptophanyl-tRNA synthase. Mutation of this gene affects amino acid homeostasis and protein synthesis in rice endosperm, resulting in abnormal expression of the genes in starch synthesis pathway which affects starch synthesis and accumulation, and eventually lead to seed development defects.

    A Preliminary Study on the Function of Rice Heading Date Gene OsDof6
    Licheng ZHANG, Yixing LI, Tiankang WANG, Mudan QIU, Shufeng SONG, Hao DONG, Lei LI, Jianfeng LIU, Li LI
    2020, 34(5): 397-405.  DOI: 10.16819/j.1001-7216.2020.0211
    Abstract ( )   HTML ( )   PDF (2948KB) ( )  

    【Objective】Our goal is to further explore the expression pattern and biological function of OsDof6, a rice Dof family transcription factor screened with the panicle development chip in the previous study. 【Method】Bioinformatics approaches were applied to analyze OsDof6 gene, protein and protein promoter sequences. The gene was edited using CRISPR/Cas9 technology. Real-time quantitative PCR and subcellular localization technology was used to reveal the gene expression pattern. 【Result】The gene promoter contains a large number of photo-, hormone-, and stress-responses and tissue expression elements. Then, two mutants of different mutation types 9522Dof6-3 and 9522Dof6-4 were obtained by using CRISPR/Cas9 technology. Through observation of the T1 generation of the mutant materials, we found that the mutants had significantly less tillers and longer heading dates (delayed by 3 days) compared to the control materials. Real-time quantitative PCR results showed that OsDof6 was expressed in varying degrees in the roots, stems, leaves and panicles, and the relative expression was significantly increased at late stages of panicle development. Subcellular localization analysis showed that OsDof6 belongs to a nuclear localization gene. 【Conclusion】OsDof6 gene affects the tiller number and heading date of rice.

    Improvement of Grain Shape and Fragrance by Using CRISPR/Cas9 System
    Shanbin XU, Hongliang ZHENG, Lifeng LIU, Qingyun BU, Xiufeng Li, Detang ZOU
    2020, 34(5): 406-412.  DOI: 10.16819/j.1001-7216.2020.0104
    Abstract ( )   HTML ( )   PDF (1549KB) ( )  

    【Objective】 CRISPR/Cas9-mediated genome editing has become an important way for molecular breeding in rice. To promote rice breeding, the non-fragrant japonica rice variety Longjing11 was used as the test material. This study aims to edit GS3, GS9 and Badh2 genes for obtaining valuable and stable long-grain fragrant rice materials. 【Method】 The target genes GS3, GS9 and BADH2 were selected to construct the vector pYLCRISPR/ Cas9-GS3/ GS9/Badh2-gRNA by using CRISPR/Cas9 gene editing technology. The Agrobacterium-mediated transformation was used to transform Longjing11. Specific mutations were introduced into the GS3, GS9 and Badh2 genes in Longjing 11. 【Result】 The grain length of the transgenic free homozygote gs3/gs9/badh2 increased by 26.43% to 27.01%, yield per plant by 10.82% to 12.11%, 1000-grain weight by 18.34% to 41.36%, rice became fragrant as compared with wild type of Longjing 11. This study efficiently transformed round-grain rice into long-grain fragrant rice. 【Conclusion】The homozygous mutant lines featured by stable inheritance and long-grain fragrant quality were obtained by using CRISPR/Cas9 system. This study provides a convenient and effective way of combining multiple quality traits together, which could significantly accelerate breeding process from a breeding perspective.

    Analysis of Blast Resistance Genes and Neck Blast Resistance of japonica Rice Varieties/Lines Recently Developed in Jiangsu Province
    Xiaoqiu WANG, Haibo DU, Xijun CHEN, Mingyou LI, Jianan WANG, Zhiwen XU, Zhiming FENG, Zongxiang CHEN, Shimin ZUO
    2020, 34(5): 413-424.  DOI: 10.16819/j.1001-7216.2020.0208
    Abstract ( )   HTML ( )   PDF (3230KB) ( )  

    【Objective】Evaluating the breeding potential of the known blast resistance (R) genes harbored in rice varieties is one of prerequisites for developing rice blast resistant varieties and R genes-based control of the disease epidemic. 【Method】A total of 195 new japonica varieties/lines from Jiangsu Province were genotyped using functional markers corresponding to 14 rice blast R gene loci. In order to identify gene or gene combination with breeding potential against neck-blast, 158 japonica rice varieties were then artificially inoculated with blast strains as well as 17 advanced backcrossing lines containing Pigm gene in two different genetic backgrounds at booting stage. 【Result】Most varieties carried 2 to 5 R genes, and none of new varieties contained Pigm; the distribution frequencies of Pib, Pita and Pikh were relatively high and all exceeded 45%, the rest 10 genes were under 30%; Pid3, Pid2, Pia and Pb1 had apparently higher frequency in lines from regional tests than that in authorized and released varieties. Three genes with effects ordered as Pia > Pi3/5/i > Pita significantly contributed to neck-blast resistance, and significantly positive interaction effects were found between Pia and Pita, and between Pi3/5/i and Pita. Combination effect of Pia+Pita was significantly higher than that of Pi3/5/i+Pita, and the varieties harboring Pia+Pita reached resistant or highly resistant levels. The resistance of 17 advanced backcrossing lines carrying Pigm was all significantly improved as compared with corresponding controls, and all reached resistant level or even higher. 【Conclusion】 The results suggested that Pigm and the combination of Pia+Pita have critically important breeding potential in japonica rice breeding against neck blast in Jiangsu Province.

    Differences in Grain Yield and Quality in Main and Ratoon Rice in Southern Henan Province
    Hao WANG, Xiangchen LIU, Qiang ZHANG, Guilong YU, Wendi ZHANG, Jian HUANG, An ZHU, Lijun LIU
    2020, 34(5): 425-434.  DOI: 10.16819/j.1001-7216.2020.0106
    Abstract ( )   HTML ( )   PDF (500KB) ( )  

    【Objective】 The combination of mid-season rice+ratoon rice is a new pattern of rice planting in southern Henan Province. However, the changes in grain yield and quality between the main and ratoon seasons remain unclear. Clarifying the changing law of grain yield and rice quality can lay a theoretical and practical basis for the screening of ratoon rice varieties with higher grain yield and better rice quality in southern Henan Province. 【Method】 In this study, 12 hybrid indica rice combinations suitable for single-cropping rice were used as materials under local high-yield cultivation conditions. The tested combinations were divided into four types according to their yields in main and ratoon seasons: BH, both high grain yields in main and ratoon season; HL, high grain yield in main season and low grain yield in ratoon season; LH, low grain yield in main season and high yield in ratoon season; BL, both low grain yields in main and ratoon seasons. The difference in rice quality was also analyzed. 【Result】 1) The processing quality and appearance quality in ratoon season were significantly improved, however, the protein contents decreased, and the eating quality of rice was improved to different extents as compared with those in main season; 2) Except for BL type (only one combination, Shenliangyou 11), the processing quality of BH and HL was better, and HL has better appearance quality and cooking and eating quality. There was no significant difference in protein contents among different yield types in main season, while in ratoon season, the protein contents in BH were 10.7 % higher than those in HL, and 1.75% lower than those in LH. 3) The effect of daily average temperature after full heading on grain quality was far greater than the sunshine hours, and the relatively low average daily temperature after full heading in ratoon season was the main reason for its better grain quality. 【Conclusion】 Based on higher grain yield and better rice quality, Liangyou 6326, Tianliangyou 616, Guangliangyou 476 and Fengliangyouxiang 1 were suitable varieties for ratoon cultivation in southern Henan Province.

    Effects of Different Seedling Raising Trays on Plant Type and Grain Yield of Machine-Transplanted Double Cropping Rice
    Chun YE, Yanda LI, Zhongsheng CAO, Junbao HUANG, Binfeng SUN, Shifu SHU, Luofa WU
    2020, 34(5): 435-442.  DOI: 10.16819/j.1001-7216.2020.9131
    Abstract ( )   HTML ( )   PDF (1196KB) ( )  

    【Objective】The objective is to elucidate the effects of different seedling raising trays on plant type and yield of machine-transplanted double cropping rice. 【Method】Field experiments were conducted in Jiangxi in 2019, involving two early and two late rice cultivars and three types of nursery trays [blanket tray(CK), bowl tray(D1) and bowl-blanket tray(D2)]. The changing characteristics of plant morphology and yield components were systematically measured. 【Result】The results indicated that: 1) The seedling quality of different seedling raising trays followed the trend of CK>D1>D2. The whole transplanting quality of seedlings under D2 was the best, as reflected by lower floating rate, injure rate and missed rate of seedling than CK. 2) Under D2 treatment, the seedlings turned green quickly and tillering was accelerated after jointing stage. The average number of tillers at booting stage was D2 > D1 > CK, which effectively increased the tiller number and panicle number and directly promote the yield. In the booting stage of early and late rice, the SPAD value of seedling leaves under D2 treatment was 3.2% higher than that under D1, and 9.2% higher than that under CK treatment, which effectively promoted photosynthesis and provided nutrition guarantee for increasing yield; 3) The yield data showed that D2 treatment had the highest yield in early rice, 13.04% and 1.65% higher than CK and D1, 30% and 19% higher than CK, respectively, and 20% higher than CK on average; The high yield of D2 treatment was due to its high chlorophyll contents in leaves, high effective panicle number, high seed setting rate and 1000-grain weight. 【Conclusion】Compared with the blanket nursing tray and bowl tray, the bowl-blanket tray can raise seedling quality and grain yield, which has a potential to be widely applied for high yield cultivation in double cropping rice production.

    Effects of Exogenous Materials on Nitrogen Photosynthetic Efficiency and Yield Formation of japonica Rice in Cold Region Under Cold Water Stress at Booting Stage
    Yan JIA, Liang YANG, Detang ZOU, Zhaojun QU, Jingguo WANG, Hualong LIU, Jin WANG, Hongwei ZHAO
    2020, 34(5): 443-456.  DOI: 10.16819/j.1001-7216.2020.0307
    Abstract ( )   HTML ( )   PDF (1444KB) ( )  

    【Objective】Our goal is to develop disaster-reducing, production-preserving and chemical-controlling cultivation techniques to effectively resist cold damage at the booting stage of japonica rice in cold region. 【Method】The split plot design and the central combination test design were used to screen out the optimal application concentrations of CaCl2, glutamic acid(Glu), and γ-aminobutyric acid(GABA) through the membership function values of yield-related indicators under cold-water stress at booting stage. 【Result】1) Under cold water stress at the booting stage, the optimal concentrations of exogenous CaCl2, Glu and GABA (CGG) were 1.87 mmol/L, 2.76 mg/L, 4.40 mmol/L, respectively and the average membership function value is the largest (0.932). 2) Compared with normal irrigation, the nitrogen photosynthetic efficiency of cold-region japonica rice decreased under cold stress at the booting stage. Compared with cold water stress at the booting stage, CGG application at the optimal concentration significantly increased the leaf area index (5.37%) and nitrogen photosynthetic efficiency (4.53%) of Dongnong 428 at the full heading stage; significantly increased leaf biomass per leaf area (2.56%) and leaf area index (3.39%) of Songjing 10 at the full heading stage. 3) Compared with cold water stress at the booting stage, the application of the optimal concentration of CGG increased the dry matter accumulation from heading stage to maturity in the cold-region japonica rice, but it was still lower than that of the normal irrigation, and there were differences between varieties and treatments. 4) Compared with cold water stress at booting stage, the yield and yield components of cold-region japonica rice increased with the application of the optimal concentration CGG, and the impact on cold-sensitive varieties was more significant. 5) Compared with the cold water stress at the booting stage, the average increase in temperature production efficiency of Dongnong 428 and Songjing 10 was 5.55% and 23.72% under the optimal concentrations of CGG, respectively. The contribution rate of exogenous CGG to the gap of temperature production efficiency is 8.99%.【Conclusion】The application of the optimal concentration of CGG under cold water stress at the booting stage promoted leaf growth of cold-region japonica rice at the full heading stage and increased the population nitrogen photosynthetic efficiency, which was beneficial to dry matter accumulation and yield formation after heading stage, thereby reducing the loss of cold-region japonica rice under cold water stress at booting stage and improving the temperature production efficiency of cold-region japonica rice.

    Difference in Growth Characteristics, Utilization of Temperature and Illumination of Double- Cropping High Quality Late Rice in Different Ecological Regions of the Lower Reaches of the Yangtze River
    Chunmei XU, Lilun YUAN, Song CHEN, Guang CHU, Weifa YE, Yuhua DING, Danying WANG, Xiufu ZHANG
    2020, 34(5): 457-469.  DOI: 10.16819/j.1001-7216.2020.9117
    Abstract ( )   HTML ( )   PDF (655KB) ( )  

    【Objective】Under machine-transplanting conditions, four different types of late rice cultivars with high quality were used to investigate the differences of yield, growth characteristics, utilization of temperature and illumination. The results will lay a theoretical basis for the selection of double-cropping late rice varieties suitable for different ecological regions in the lower reaches of the Yangtze River. 【Method】The yield, growth duration, dry matter accumulation, and utilization of temperature and illumination of double-cropping late rice were comparatively studied using four kinds of rice varieties as test materials namely indica conventional rice, indica hybrid rice, japonica conventional rice and Changyou japonica hybrid rice (20 varieties in total, selected between 2016 and 2017, all of which were high-quality rice in the lower reaches of the Yangtze River as double-cropping late rice). The experiment was carried out in two cities, Fuyang, Zhejiang Province (30.05º N, 119.95º E, 17.93 m above sea level) and Lujiang, Anhui Province (31.15º N, 117.16º E, 14 m above sea level). 【Result】The yield of the four-types of late rice at high latitude was higher than that at low latitude. The yield of indica conventional rice, indica hybrid rice, japonica conventional rice, and Changyou japonica hybrid rice grown in Lujiang, Anhui Province was 11.1%, 12.9%, 6.6% and 12.4% higher than that in Fuyang, Zhejiang Province. When planted in the same places, Changyou japonica hybrid rice had the highest yield, and conventional indica rice had the lowest. The growth period was longer and dry matter accumulation was higher at high latitudes. When planted at high altitudes, the indica hybrid rice growth duration was the longest (10.4 d), and the increase in dry matter accumulation was the largest in conventional japonica rice (11.93% in full heading stage and 9.44% in mature stage). When planted in the same place, the dry matter accumulation was higher in hybrid rice than conventional rice. There was no significant difference in effective accumulated temperature between the filling stage and the whole growth duration of indica rice, but the sunshine hours, solar radiation, and its utilization rate were significantly higher at high latitudes. The effective accumulated temperature decreased significantly in the filling stage and the whole growth stage of japonica rice, but the change of accumulated sunshine hours was not obvious, while the accumulated solar radiation increased significantly at high latitudes. These were consistent with the changing trend of the utilization rate of the temperature and light resources. When planted at the same latitude, the growth period, dry matter accumulation, temperature and light resource utilization rate of japonica rice were higher than those of indica rice. 【Conclusion】Late indica rice could make full use of temperature and light resources in order to improve its yield when planted in Lujiang, Anhui Province, but the difference of the utilization efficiency in the temperature and light resources of late japonica rice was not obvious. The yield of late japonica rice in Lujiang, Anhui Province increased because of the extension of the growth duration and the increase of dry matter accumulation.

    Extracellular Antimicrobial Substances Produced by Bacillus subtilis JN005 and Its Control Efficacy on Rice Leaf Blast
    Huajun ZHU, Hu ZHOU, Zuohua REN, Erming LIU
    2020, 34(5): 470-478.  DOI: 10.16819/j.1001-7216.2020.9109
    Abstract ( )   HTML ( )   PDF (2520KB) ( )  

    【Objective】The purpose of this research is to assay stability, biological activity and efficacy of the extracellular antimicrobial substances produced by Bacillus subtilis JN005 against Magnaporthe oryzae. 【Method】The antimicrobial substances produced by B. subtilis JN005 was tested using different media. The activity of extracellular antimicrobial substances of JN005 strain against M. oryzae and its efficacy on rice leaf blast were measured by dural culture, optical microscope observation, indoor detached-leaf inoculation and live inoculation. 【Result】B. subtilis JN005 secreted protease, cellulase, amylase and β-1,3-glucanase and its extracellular antimicrobial substances showed inhibition activity against M. oryzae. The extracellular antimicrobial substances were stable in a wide range of pH values from 2 to 12 and at temperatures from 0℃ to 100℃. The antifungal activity was retained after treatment with proteinase K. The extracellular antimicrobial substance kept its activity even it was irradiated for 12 h under ultraviolet light or exposed to 4℃ for 3 months. The extracellular antimicrobial substances caused distortion of hyphae of M. oryzae, and hindered the germination of conidia. Indoor detached leaves inoculation of Xiangwanxian 12 showed that disease incidence was 34.07% as rice leaves were treated with 100-fold dilution of the extracellular antimicrobial substances, followed by inoculation with conidia suspension of M. oryzae (after 24 h). The control efficacy was close to that of 500 times-diluted 40% isoprothiolane EC. The disease incidence was 38.52% as rice leaves were inoculated with conidia suspension of M. oryzae and treated with 100-fold dilution of the extracellular antimicrobial substances after 24 h, significantly different from 1500 times-diluted 75% tricyclazole WP and 500 times-diluted 40% isoprothiolane EC. The potted plant experiment showed that efficacy was 75.32% as rice was inoculated with conidia suspension of M. oryzae followed by spraying 100-fold dilution of the extracellular antimicrobial substances before 24 h. The efficacy was 71.49% as rice was inoculated with conidia suspension of M. oryzae and followed by spraying of 100-fold dilution of the extracellular antimicrobial substances after 24 h. 【Conclusion】The extracellular antimicrobial substances produced by JN005 strain directly inhibited mycelial growth and conidia germination of M. oryzae and it has good environmental stability. The extracellular antimicrobial substances have better preventative efficacy and therapeutic efficacy on rice blast and should be further investigated and developed as such.