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10 September 2022, Volume 36 Issue 5 Previous Issue    Next Issue
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Analysis and Prospects of Extension of Main Varieties of Hybrid Rice with High Quality in China ZENG Bo, GONG Junyi, ZHANG Fang 2022, 36(5): 439-446.  DOI: 10.16819/j.1001-7216.2022.220408 Abstract ( )   HTML ( )   PDF (13466KB) ( )   【Objective】The recent ten-odd years have marked an important transition when the quality of hybrid rice has been promoted under the guidance of revised and approved standards. Reviewing the breeding and extension process of high-quality hybrid rice in this period is of great significance for guiding rice breeding in the future. 【Method】 Based on rice materials and data including the extension area of main hybrid rice varieties in China from 2009 to 2020, we analyzed the extension area of male sterile lines, restorer lines and series of varieties, and reviewed the replacement process of major varieties in each rice cropping region. 【Result】 During this period, the extension area of hybrid rice varieties with high quality in China kept growing rapidly, and the high-quality-rice rate in term of planting area in main rice cropping regions increased significantly, but there was still a lack of high-grade rice varieties with high quality. The results also showed that the existing main hybrid rice varieties with high quality were derived from 15 male sterile lines and 9 restorer lines. In addition, the analysis results showed that the major hybrid rice varieties with high quality in different rice cropping regions in China had been replaced on a large scale for 1-2 times. 【Conclusion】 Over the past 12 years, driven by the innovation of rice breeding technology, the process of high-quality hybrid rice breeding in China has been significantly accelerated, a large number of high-quality hybrid rice varieties have emerged in various rice cropping regions, the planting area has increased rapidly, and the proportion of high-quality varieties applied in production has increased significantly.

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Transcriptome Analysis of Young Rice Panicles in Early Response to Exposure to Mycotoxin of Ustilaginoidea virens FU Rongtao, WANG Jian, CHEN Cheng, ZHAO Liyu, CHEN Xuejuan, LU Daihua 2022, 36(5): 447-458.  DOI: 10.16819/j.1001-7216.2022.210714 Abstract ( )   HTML ( )   PDF (28637KB) ( )   【Objective】 Rice false smut caused by Ustilaginoidea virens not only leads to rice yield loss, but also produces mycotoxins which is toxic to animals and plants. In order to elucidate the molecular mechanism behind the response to exposure to mycotoxin the young panicles of rice were mycotoxin-treated with U. virens mycotoxin, which may provide a new idea for exploring rice false smut resistance genes and molecular breeding for disease resistance. 【Method】Transcriptome sequencing was performed with mycotoxin-treated young panicles as materials. The genome of 9311 was used as the reference genome to align the sequences. The expression level of genes was calculated by the term of Transcripts Per Million (TPM). According to the database, the differentially expressed genes were screened by parameters (|LOG2 fold change|≥1 and q-value≤0.05). Combined with differential expression analysis and function annotation, the key genes in response to mycotoxin were identified in rice panicles. The differentially expressed genes were verified by qRT-PCR. 【Result】2526 differentially expressed genes (DEG) were identified in young panicles of rice after 12 h treated with mycotoxin. Through GO enrichment, KEGG metabolic pathway and KOG function analysis, the DEGs were divided into 64 terms under GO function, 32 metabolic pathways and 23 categories under KOG function, including starch and sucrose metabolism, phenylpropyl biosynthesis, carbon metabolism, glycolysis/gluconeogenesis, amino sugar and nucleoside sugar metabolism and other biological processes. There were 66 plant transcription factors in DEGs, which belonged to 7 family of plant transcription factors, including WRKY and Myb. The expression levels of OsCPS2, OSKSL4 and cytochrome P450 were up-regulated, while the expression levels of amylase, beta-fructofuranosidase and UGPase were down-regulated when we analyzed genes involved in diterpenoid biosynthesis and starch and sucrose metabolism pathways. Therefore, it is speculated that these genes play an important role in rice response to mycotoxin of U. virens stress. 【Conclusion】As an abiotic stress factor, mycotoxin of U. virens had a toxic effect on young panicles of rice. It affects the synthesis of nutrients in seeds by interfering with metabolism of starch and sucrose, and thus reduces the resistance of rice to pathogen infection.

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Improvement of Herbicide Resistance in Rice by Using CRISPR/Cas9 System YIN Liying, ZHANG Yuanye, LI Rongtian, HE Mingliang, WANG Fangquan, XU Yang, LIU Xinxin, PAN Tingting, TIAN Xiaojie, BU Qingyun, LI Xiufeng 2022, 36(5): 459-466.  DOI: 10.16819/j.1001-7216.2022.211004 Abstract ( )   HTML ( )   PDF (932KB) ( )   【Objective】 It is of great significance to create herbicide-resistant rice varieties. The acetyllactic acid synthase (ALS) gene was edited to create rice varieties with excellent herbicide resistance using non-herbicide-resistant japonica rice varieties with good quality as materials. 【Methods】Using CRISPR/Cas9 technology, the single-base mutant vector pH-NCas9-PBA-ALS was constructed with acyllactic acid synthase (ALS) as the target gene. Songjing 22, Longjing 46 and Suijing 18 were used as transformation materials to obtain transgenic plants through Agrobacterium-mediated genetic transformation. Genotypes and phenotypes were identified by sequencing the mutation sites of transgenic plants and herbicide spraying test. 【Results】 Ten ALSS627N mutants, one ALSS627N and 1884G-A(the 628th amino acid unchanged mutant), and one ALSS627N/G628E mutant were obtained by molecular level detection. Compared with the wild type, the three types of mutants had stronger herbicide resistance. 【Conclusion】 Using CRISPR/Cas9 gene editing technology, we obtained homozygous mutant lines which are genetically stable and herbicide-resistant, providing basic materials for herbicide-resistant rice breeding.

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Construction and Verification of Vector Containing Glyphosate Resistance Selection Marker for Multiplication of Common Genic Male Sterile Lines in Rice LI Yanyao, DENG Lihua, LI Xinyan, LI Hua, QIN Guannan, WENG Lüshui, YU Jianghui, LI Jinjiang, XIAO Guoying 2022, 36(5): 467-475.  DOI: 10.16819/j.1001-7216.2022.211226 Abstract ( )   HTML ( )   PDF (2828KB) ( )   【Objective】 The hygromycin resistance gene is often used as a selection marker in expression vectors for multiplication of common genic male sterile (CGMS) lines in rice. The glyphosate resistance gene replaces the hygromycin resistance gene as it not only gives the multiplication line glyphosate resistance, but also bypasses the current policy restrictions on the use of antibiotic marker genes in genetically modified crops. 【Methods】 An expression vector pC3300-Epsps-AA-Eat-Red was constructed by using homologous recombination method in order to multiply the rice CGMS line with eat1 mutation gene, which harbors the glyphosate resistance gene Epsps#, pollen lethal gene ZmAA1, CGMS restorer gene OsEat1 and red fluorescent gene DsRed2. Agrobacterium-mediated transformation method was adopted. 【Results】 Transformation of indica rice line 9K19-5 produced 318 regenerated plants of the CGMS multiplication line Eat9K that could restore the sterility of eat1 and resist glyphosate. The phenotype identification of single copy transformant Eat9K-3 showed that: there were two kinds of pollens in anthers, one was fertile and the other was sterile; the seeds included two types, one was with fluorescence and the other was without fluorescence; the seedlings from fluorescent seeds tolerated at least 1 g/L glyphosate. In addition, this study established a four-primer detection method to distinguish the wild-type gene Eat1 from the genic male sterile gene eat1. 【Conclusion】 This study not only verified the effectiveness of the expression vector, but also created the new germplasm of CGMS multiplication line with herbicide resistance, as well as established a four-primer detection method to distinguish the wild-type gene Eat1 from genic male sterile gene eat1.

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Salicylic Acid Alleviates Low Phosphorus Stress in Rice via a Nitric Oxide-dependent Manner ZHU Chunquan, WEI Qianqian, DANG Caixia, HUANG Jing, XU Qingshan, PAN Lin, ZHU Lianfeng, CAO Xiaochuang, KONG Yali, XIANG Xingjia, LIU Jia, JIN Qianyu, ZHANG Junhua 2022, 36(5): 476-486.  DOI: 10.16819/j.1001-7216.2022.210813 Abstract ( )   HTML ( )   PDF (1815KB) ( )   【Objective】It is of great importance to analyze the physiological and molecular mechanisms of salicylic acid(SA) regulating the response of rice to phosphorus(P) stress. 【Method】The conventional rice cultivar Nipponbare was used in our experiment, and the total P content, acid phosphatase activity, xylem P concentration, root parameters, expression levels of P transporter genes and nitric oxide (NO) content in rice were measured after exogenous SA application to explore the physiological and molecular mechanism that SA alleviates P deficiency stress in rice. 【Result】 1) Application of 1 μmol/L SA significantly increased the total P content in rice under low P conditions. However, 5 μmol/L SA decreased the total P content in rice, indicating SA had a dose effect on the regulation of P absorption in rice. 2) Application of 1 μmol/L SA significantly increased the activity of acid phosphatase by 11.35%, total root length by 20.90%, surface area by 11.86%, root volume by 15.38%, total root number by 23.55%, xylem P concentration by 22.6%. In addition, the application of 1μmol/L SA significantly increased the expression levels of P transporter genes, thereby increased the absorption of exogenous P and the transportation of internal P in rice under low P conditions. 3) SA increased the content of NO in rice roots by increasing the activity of nitrate reductase, so as to improve the absorption of P in rice under low phosphorus conditions via regulating the expression of P transporter genes. 【Conclusion】SA alleviates low phosphorus stress in rice by its interacting with the signal molecule of NO.

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Effects of Low Temperature Stress During Grain Filling on Starch Formation and Accumulation of Superior and Inferior Grains in Rice CHEN Hongyang, JIA Yan, ZHAO Hongwei, QU Zhaojun, WANG Xinpeng, DUAN Yuyang, YANG Rui, BAI Xu, WANG Changcheng 2022, 36(5): 487-504.  DOI: 10.16819/j.1001-7216.2022.211105 Abstract ( )   HTML ( )   PDF (3257KB) ( )   【Objective】Our purposes are to illuminate the effects of low temperature stress during grain filling on the contents, accumulation rates and key enzyme activities of starch components in superior and inferior grains in rice, to clarify the regulatory effect of changes in the activities of key enzymes in starch synthesis on the rate of starch accumulation and to explore the effect of difference in granule starch formation and accumulation in superior and inferior grains on rice yield formation. 【Method】This experiment was carried out with the chill-tolerant variety Dongnong 428 and chill-sensitive variety Songjing 10 as the test materials at room temperature (daytime temperature 28℃, 14 h/night temperature 22℃, 10 h; 7 days), and low temperature (17℃, four treatments). The low temperature treatments lasted 1, 3, 5, and 7 days(abbreviated to D1, D3, D5 and D7), respectively. The difference in the accumulation of starch components of superior and inferior grains and the changes in the activities of key synthesizing enzymes under low temperature stress during grain-filling period were analyzed. 【Result】Compared with the control, low temperature stress during grain filling period reduced the peak activities of adenosine diphosphoglucose pyrophosphorylase (AGPase), soluble starch synthase (SSS), starch branching enzyme (SBE) and the contents of amylopectin and total starch in the superior and inferior grains of the two rice varieties, improved granule-bound starch synthase (GBSS) activity and amylose content in D3, D5, and D7 treatments 28－38 days after heading. Compared with the control, the highest enzyme activity and the fastest accumulation of starch in low temperature treatments occurred at a later time, and the D7 treatment had the greatest impact. The contents of amylopectin and total starch of the superior and inferior grains in D7 decreased most on the 13th and 18th days after heading, and the amylose content increased most on the 28th day after heading. Correlation analysis showed that the amylose content of superior and inferior grains and the content of superior amylopectin and total starch are extremely significantly positively correlated with their maximum accumulation rates. The accumulation of inferior grain amylopectin and total starch is also related to the time to reach the maximum accumulation rate. The changes in the activities of AGPase, GBSS, SSS, and SBE are closely related to the accumulation rate and time of starch accumulation, and have a significant impact on the changes in starch and starch component contents. At the same time, low temperature stress during the grain filling stage significantly reduced the thousand-grain weight, seed setting rate and yield of rice, and the decrease gradually increased with the increasing low temperature treatment days. Low temperature stress during the grain filling stage has a greater impact on the changes in the key enzyme activities of starch synthesis in the inferior grains than the superior ones. The starch synthesis and accumulation of inferior grains slowed down and the content decreased, resulting in a significant decrease in thousand-grain weight and yield. 【Conclusion】In terms of varieties, the cold-tolerant Dongnong 428 has relatively high key enzyme activities of starch synthesis, and the contents of starch and its components is relatively high, so that the rice yield can be maintained at a relatively high level under low temperature stress. Therefore, the key enzyme activities of starch synthesis of granules in superior and inferior grains play a very critical role in the regulation of starch synthesis, and the changes and levels of starch components have a very important impact on yield.

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Response of Grain Quality and Root Characteristics to Irrigation Methods During Mid-season indica Rice Varieties Improvement JING Wenjiang, GU Hanzhu, ZHANG Xiaoxiang, WU Hao, ZHANG Weiyang, GU Junfei, LIU Lijun, WANG Zhiqin, YANG Jianchang, ZHANG Hao 2022, 36(5): 505-519.  DOI: 10.16819/j.1001-7216.2022.211104 Abstract ( )   HTML ( )   PDF (3339KB) ( )   【Objective】It is important to have a deep insight into the grain quality and root characteristics of different types of mid-season indica rice varieties in different irrigation methods. 【Method】The representative mid-season indica rice varieties in Jiangsu Province in recent 80 years were used as experimental materials, AWD(alternate wetting and drying irrigation) and CI(conventional irrigation) were conducted during the whole growth period of rice. Two dwarf varieties, two semi-dwarf varieties and two semi-dwarf hybrid varieties with obvious difference in water use efficiency(WUE) were selected to analyze grain quality and root characteristics. 【Result】Under AWD or CI, grain yield and WUE of all varieties increased gradually with variety improvement. Compared with CI, AWD significantly increased yield and water use efficiency. Under AWD, the yield of various varieties(dwarf variety, semi-dwarf variety and semi-dwarf hybrid variety) was 6.96, 8.71 and 10.14 t/hm2, respectively, WUE was 1.30, 1.62 and 1.91 kg/m3, respectively. The milled rice rate, head milled rice rate, protein content, solubility, swelling capacity of starch, root dry weight and root-shoot ratio, root oxidation activity, root total absorbing surface area and active absorbing surface area, contents of zeatin, zeatin nucleoside and abscisic acid in root bleeding sap were significantly increased with the improvement of varieties. Compared with CI, AWD improved the appearance quality and root morphological and physiological characteristics, increased the peak viscosity, hot viscosity, final viscosity and breakdown of rice starch, decreased the setback and relative crystallinity of starch. Correlation analysis showed that yield and WUE were closely related to grain quality and root growth. 【Conclusion】Modern semi-dwarf varieties, especially semi-dwarf hybrid variety, could obtain higher yield, water use efficiency and better grain quality under AWD during the whole growth period, which was closely related to the improvement of root morphology and physiological characteristics.

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Characteristics of Grain Protein Accumulation and Its Response to Nitrogen Level in Good Taste Rice Varieties LU Dandan, YONG Mingling, TAO Yu, YE Miao, ZHANG Zujian 2022, 36(5): 520-530.  DOI: 10.16819/j.1001-7216.2022.220311 Abstract ( )   HTML ( )   PDF (4036KB) ( )   【Objective】The aim of this study is to clarify the protein accumulation characteristics in grains of rice varieties with good taste and the effects of nitrogen level. 【Method】Conventional japonica and hybrid rice varieties with different taste values were used as materials, and different nitrogen application levels were set at filling stage to investigate the cooking and eating quality of the varieties at different nitrogen application levels and its relationships with rice protein and its component contents. In addition, the dynamic changes of amino acid contents and protein contents in different grain parts at different nitrogen levels were further analyzed, and finally the characteristics of grain protein accumulation and its response to nitrogen level in rice varieties with good taste were summarized. 【Result】The grain protein contents of good taste varieties was relatively low, and increased with the increasing nitrogen level. Also, good taste varieties had higher breakdown viscosity, but lower setback viscosity, and the cooking and eating quality was less affected by nitrogen levels. The protein component contents of good taste rice varieties were lower, and there was a significant negative correlation between protein content and eating quality. In conventional japonica varieties, rice taste value was negatively correlated with the contents of albumin, globulin and gliadin; in hybrid varieties, rice taste value was negatively correlated with the contents of gliadin and glutenin. The contents of free amino acids and protein accumulation in rice varieties with good taste were lower during grain filling. However, the varieties with poor taste had higher level of amino acid at grain filling stage. The grain protein contents were higher at maturity, and the effect of nitrogen level on improving grain protein content was more significant. 【Conclusion】The low protein content in grains of good taste varieties was closely related to the low protein synthesis and accumulation during grain filling, and was less affected by nitrogen level.

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Effects of Simplified Application of Dedicated Fertilizer on Yield, Fertilizer Use Efficiency and Economic Benefit in Rice-ratoon Rice System WANG Minyu, DAI Zhigang, YU Defang, WANG Xiangping, GUAN Shaohua, SHAO Yuangang, ZHANG Jiaxue, LI Xiaokun 2022, 36(5): 531-542.  DOI: 10.16819/j.1001-7216.2022.210808 Abstract ( )   HTML ( )   PDF (2037KB) ( )   【Objective】The effects of simplified application of dedicated fertilizer on yield, yield components, fertilizer use efficiency and economic benefit were studied and clarified in the system of rice-ratoon rice to lay a theoretical basis for the simplified and scientific fertilization. 【Method】Multi-site field experiments were designed with no fertilizer (T1), local farmers’ practice (T2) and dedicated and simplified fertilizer (T3). The yield, yield components, nitrogen, phosphorus and potassium concentration of different treatments were determined to calculate the nutrient accumulation, fertilizer use efficiency and economic benefit. 【Result】Fertilization could significantly increase the yield of rice. Compared with T1 treatment, the main rice and ratoon rice in nine experimental sites under T2 treatment increased by 56.0% and 89.4%, respectively; For T3 treatment, by 75.3% and 108.9%. Compared with T2 treatment, the total grain yield of T3 treatment in the main season, the ratooning season and the two seasons increased by 1006 kg/hm2, 356 kg/hm2 and 1362 kg/hm2, with increasing rates of 12.4%, 10.3% and 11.8%. Compared with T2 treatment, the number of grains per panicle of T3 treatment increased by 20 grains or 10.5%. The results showed that the Nitrogen (N), Phosphorus (P2O5) and Potassium (K2O) accumulation in the main season in above-ground rice plants increased by 7.4%, 6.8% and 10.2% in T3 treatment. Compared with T2 treatment, the ratoon rice increased by 5.9%, 16.6% and 24.4%. The partial factor productivity from applied N, apparent recovery efficiency of applied N and agronomic efficiency of applied N of T3 treatment at different experimental sites increased, with the highest increase of 25.3%, 93.8% and 143.7%, respectively as compared with T2 treatment. In the nine experimental sites, net income increased by 6.19×103 Yuan/hm2 on average. 【Conclusion】The results showed that the application of dedicated and simplified fertilizer could significantly increase the rice yield, the nutrient uptake of above-ground parts, and improve the fertilizer use efficiency, reduce the times of fertilization and increase economic benefits.

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Effect of Elevated CO2 Concentration on Rice Growth and CH4 Emission from Paddy Fields Under Straw Incorporation ZENG Wenjing, QIU Lanying, CHEN Junjie, QIAN Haoyu, ZHANG Nan, DING Yanfeng, JIANG Yu 2022, 36(5): 543-550.  DOI: 10.16819/j.1001-7216.2022.210811 Abstract ( )   HTML ( )   PDF (931KB) ( )   【Objective】The aim of this study is to clarify the effects of increased atmospheric CO2 concentration on rice growth and CH4 emission under straw incorporation, so as to provide theoretical reference and lay a scientific basis for greenhouse gas emission assessment for rice production technology innovation concerning high yield and low carbon emission under climate change. 【Method】Field experiments were conducted in Open Top Chambers (OTC). Two CO2 concentrations were designed, namely, ambient atmospheric CO2 concentration (0.04%, aCO2) and elevated atmospheric CO2 concentration (0.055%, eCO2) with an equal amount of previous wheat straw incorporation. We analyzed the effects of eCO2 concentration on rice yield and growth, CH4 emission and the abundance of related microorganisms from paddy fields under straw incorporation, which could illustrate the influence mechanism of eCO2 on CH4 emission under that conditions. 【Result】The results showed that eCO2 significantly promoted rice growth, i.e., eCO2 increased flag leaf area, aboveground biomass and rice yield by 25.0%, 22.0%, and 29.0%, respectively. Elevated atmospheric CO2 concentration significantly increased the number of panicles, seed setting rate and 1000-grain weight, but eCO2 have no effect on the number of grains per panicle. Under straw incorporation, eCO2 trended to mitigate the CH4 emission from rice paddies and reduced the yield-scared CH4 emission by 39.4%. Elevated atmospheric CO2 concentration increased the copy numbers of pmoA, a key gene for methane oxidation in soil, by 20%, but had little effect on the copy number of mcrA, a key gene for methane production. 【Conclusion】Under the straw incorporation, eCO2 not only improves rice yield but also reduces CH4 emission from rice paddies.