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10 September 2019, Volume 33 Issue 5 Previous Issue    Next Issue
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Reviews and Special Topics

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Research Advances on Molecular Genetic Mechanism for Cadmium Absorption and Transportation in Rice Shilin DING, Chaolei LIU, Qian QIAN, Zhenyu GAO 2019, 33(5): 383-390.  DOI: 10.16819/j.1001-7216.2019.9040 Abstract ( )   HTML ( )   PDF (607KB) ( )   Cadmium is one of the heavy metals with serious toxicity to human health. The main source of cadmium in the human body is the consumption of rice with high levels of cadmium. Therefore, it is important to clarify the genetic mechanism of cadmium uptake, transport and accumulation in rice. So far, although the genetic pathway of cadmium accumulation has not been fully clarified in rice, the regulatory role of some genes in cadmium accumulation has been testified. Here, we briefly summarize the harm of cadmium stress on rice, the variation of cadmium accumulation among rice varieties, QTLs associated with cadmium accumulation in rice, genes related to cadmium absorption and transport, and application of them in rice breeding. Perspectives and research contents in the future were also advanced.

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Advances in Molecular Mechanisms of Rice Leaf Inclination and Its Application in Breeding Juan HU, Han LIN, Na XU, Ran JIAO, Zhijun DAI, Caolin LU, Yuchun RAO, Yuexing WANG 2019, 33(5): 391-400.  DOI: 10.16819/j.1001-7216.2019.9029 Abstract ( )   HTML ( )   PDF (778KB) ( )   Rice leaf inclination refers to the degree of bending between leaves and stems, which is one of the most important factors affecting plant architecture and grain yield. Leaf inclination affects leaf photosynthesis rate. Upright leaves are one of the factors of the ideal plant type of rice. Leaf inclination is regulated by a variety of genes, and is the result of interactions between various plant hormones such as brassinosteroids, auxin, gibberellin, and jasmonic acid. Other factors such as root distribution, leaf size, and growth environment also have a certain impact on the leaf inclination. Based on the research progress of rice leaf inclination, this review summarizes and elaborates on the molecular mechanism of rice leaf inclination and the application of leaf inclination in breeding from the aspects of lamina joint development, hormone levels and other factors, so as to provide reference for ideal plant type breeding and lay a theoretical foundation for further improvement of rice yield.

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Present Situation and Consideration of Seed Processing and Testing Theory and Technology Mingdong ZHU, Xiangjin WEI, Hongjun XIE, Guohua TANG, Xiaoshan ZENG, Jianlong WANG, Peisong HU, Yinghong YU 2019, 33(5): 401-406.  DOI: 10.16819/j.1001-7216.2019. 8133 Abstract ( )   HTML ( )   PDF (826KB) ( )   Seed processing and testing hold the key to the market circulation of seeds, and are an indispensable link in commercial breeding to endow seeds with commodity attributes. The research of seed processing and testing theory and technology is an important link in improving the seed industry chain, realizing large-scale commercial breeding and consolidating the seed industry science of ‘integration of breeding, propagation and promotion’. The scientific and technological system of seed industry in China is being formed and perfected, which is subject to the development level of the industry. The theory and technology of seed processing and testing are relatively weak. We reviewed the development of seed processing and testing theory and technology, and put forward strategies and suggestions to improve the sound development of China’s seed industry. In order to meet the needs of seed industry development and on the basis of high quality breeding of varieties, the new directions and demands of seed processing and testing theory and technology were analyzed. We will work to strengthen the applied research of seed industry, establish advanced seed quality inspection system, improve seed processing equipment suitable for the development needs of modern seed industry, establish standardized production system of seed processing industry, develop the scientific and technological disciplines of seed industry, and promote the sustainable and healthy development of seed industry.

Research Papers

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Creation of Low-Cd-accumulating indica Rice by Disruption of OsNramp5 Gene via CRISPR/Cas9 Qizhang LONG, Yonglan HUANG, Xiuying TANG, Huimin WANG, Ming LU, Linfeng YUAN, Jianlin WAN 2019, 33(5): 407-420.  DOI: 10.16819/j.1001-7216.2019.9026 Abstract ( )   HTML ( )   PDF (1338KB) ( )   【Objective】 To accelerate the breeding process of low-Cd-accumulating rice,【Methods】 the widely applied indica pure-line cultivars, Wushansimiao and Zhongzao 35, and the popular parents of hybrids, Huazhan and Wufeng B were used as materials to create OsNramp5 knockout lines via CRISPR/Cas9. The marker-free OsNramp5 mutants together with the wild types were grown either in a Cd-contaminated field (Field A) or in a non-Cd-contaminated field (Field B) for subsequent experiments. The changes of the grain Cd content were investigated for plants grown in both Field A and Field B. The changes of the contents of other related minerals were also examined but only for those plants grown in Field A. The agronomic changes of the mutants were further assessed by examining those plants grown in Field B. 【Results】 Rice lines with mutations at OsNramp5 were successfully generated for all the four cultivars. On one hand, the grain Cd level in OsNramp5 mutants grown in Field B was reduced by 85.5% on average (<0.02 mg/kg); as a result of OsNramp5 mutation, the Cd level in plants grown in Field A, was reduced by 94.8% (<0.1 mg/kg), meanwhile, the Mn level was decreased by 52.7%; on the contrary, the Cr level was elevated by 59.5% on average for the four cultivars and an increase of 79.1% in the Pb level was also observed but only in OsNramp5 mutants of Huazhan; the levels of other mineral elements including Fe, Cu , Zn, Ca, Se and As were slightly or hardly affected. On the other hand, a slight decrease in plant height and an average yield loss of 6.9% were observed due to OsNramp5 mutation for all cultivars; the yield loss could be ascribed to a reduction in seed setting rate and seed weight and was compensated by a slight increase in effective tiller number. 【Conclusion】 Low-Cd-accumulating rice plants can be generated by OsNramp5 disruption at the cost of an acceptable yield loss and the low-Cd-accumulating rice lines produced in the present study may serve as promising cultivars to eliminate rice Cd contamination in many areas.

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Breeding Restore Lines of Hybrid Rice by Pyramiding Genes for Resistance to White Backed Planthoppers and Brown Planthoppers Yongsheng ZHU, Jianlin BAI, Hongguang XIE, Fangxi WU, Xi LUO, Shenfei JIANG, Wei HE, Liping CHEN, Qiuhua CAI, Huaan XIE, Jianfu ZHANG 2019, 33(5): 421-428.  DOI: 10.16819/j.1001-7216.2019.9007 Abstract ( )   HTML ( )   PDF (769KB) ( )   【Objective】To breed restore lines of hybrid rice resistant to white backed planthoppers and brown planthoppers,【Method】we used B5 with brown planthopper resistance genes Bph14 and Bph15 and Fuhui 7011 with white backed planthoppers resistance gene qsI-4 as donor parents, and Fuhui 676, a main restorer line, as the recurrent parent through the molecular marker-assisted selection combined with field and indoor identification. The insect-resistant lines and their hybrid progenies were tested and their agronomic traits were analyzed. 【Result】Three restorer lines with three resistance genes to rice brown planthoppers and white backed planthoppers (Bph14, Bph15 and qsI-4) and three lines with two resistance genes were bred. Resistance identification indicated that the resistance of the restorer lines was moderately resistant or resistant. Two restorer lines with potential for production and application were screened out by examining the resistant strains and their crossing progenies and analyzing their agronomic traits.【Conclusion】This study provides new resistance germplasms against brown planthoppers and white backed planthoppers for hybrid rice breeding.

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Thermo-sensitive Male Sterile Line Created by Editing TMS5 Gene in japonica Rice Xi DU, Yunyan FEI, Fangquan WANG, Yang XU, Jun WANG, Wenqi LI, Ling ZHAO, Zhihui CHEN, Guohua LIANG, Yong ZHOU, Jie YANG 2019, 33(5): 429-435.  DOI: 10.16819/j.1001-7216.2019.9035 Abstract ( )   HTML ( )   PDF (1027KB) ( )   【Objective】The breeding of thermo-sensitive male sterile rice lines is a key step in the breeding of two-line hybrid rice. TMS5 is the key gene that modulates pollen fertility of rice at different temperatures and has been widely used in rice breeding. In order to accelerate the breeding process of thermo-sensitive sterility lines, 【Method】CRISPR/Cas9 technology was used to edit TMS5 with a japonica rice variety Wuyunjing 7 as a material. 【Results】Sequencing analysis showed that six homozygous mutants screened from 22 strains of T0 generation produced the same genetic variation, and one base “A” was inserted between 44 bp and 45 bp of the second exon of TMS5 of all the six mutants, resulting in pre-maturation of translation. Cytological observation and artificial pollination confirmed that the pollen of tms5 mutant was aborted and the development of female gametes was normal. 【Conclusion】These results indicated that the thermo-sensitive male sterile lines could be obtained rapidly by knocking out the thermo-sensitive male sterile gene TMS5 in japonica rice.

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Effects of Machine-transplanting Synchronized with One-time Precision Fertilization on Nutrient Uptake and Use Efficiency of Double Cropping Rice Xuemei ZHONG, Tieping HUANG, Jianwei PENG, Wenlu LU, Xingrong KANG, Mengfei SUN, Siming SONG, Qiyuan TANG, Yuxin CHEN, Dongzhi ZHAN, Xuan ZHOU 2019, 33(5): 436-446.  DOI: 10.16819/j.1001-7216.2019.8084 Abstract ( )   HTML ( )   PDF (1077KB) ( )   【Objective】 Our aim is to ensure the precision in rice fertilization, and to reveal the nutrient utilization characteristics of machine-transplanted rice under one-time, one-side deep fertilization with reduced nitrogen (N) application level and to improve the nitrogen utilization efficiency for double-cropping rice. 【Method】Field experiments (2017-2018) were conducted using soil-tested formulated fertilization with precise fertilizer distributor to study the effects of one-time precision fertilization on nutrient absorption and utilization of double-cropping rice system in typical growing regions, and to investigate the relationships between nutrient contents and yield.【Result】As compared with conventional fertilization treatment, the accumulations of N, P, K in machine-transplanted early rice under one-time N application rate (reduced by 10%-30%) increased by 7.9%-11.7%, 9.4%-25.9% and 2.0%-6.5% in 2017, 8.2%-15.0%, 6.9%-14.1% and 13.9%-16.7% in 2018, in late rice by -0.6%-5.7%, 9.1%-14.4% and 3.7%-19.6% in 2017, 6.1%-8.5%, 9.4%-19.3% and 18.7%-22.2% in 2018, and N recovery efficiency (NRE), N agronomic efficiency (NAE) and N partial factor productivity (NPFP) in early rice by 38.6%-92.7%, 49.9%-103.6% and 29.49%-103.6% in 2017, 36.9%-85.1%, 46.0%-98.4% and 20.7%-75.4% in 2018, and NRE, NAE, NPFP in late rice by 20.8%-43.1%, 31.3%-64.2% and 18.3%-48.5% in 2017, 26.8%-99.1%, 60.0%-82.9% and 26.6%-60.5% in 2018. The optimum treatment was obtained with a reduction of 20%-30% in N application rate．With the reduction of N application rate, NRE of double-cropping rice first increased then reduced, while NHI, NAE and NPFP were on the rise, and soil alkali-hydrolyzale N declined. 【Conclusion】The integration and optimization of fertilization technology and machine-transplanted technique can effectively reduce N application rate, facilitating N, P, K accumulation and utilization, which is conducive to raise grain yield and N use efficiency of double-cropping rice.

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Effects of Reduced Urea Application on Yield and Photosynthetic Characteristics of Mechanically-transplanted Rice Under Different Planting Spaces Haiyue WANG, Qiao ZHANG, Yunxia WU, Fengjun YAN, Changchun GUO, Yongjian SUN, Hui XU, Zhiyuan YANG, Jun MA 2019, 33(5): 447-456.  DOI: 10.16819/j.1001-7216.2019.9021 Abstract ( )   HTML ( )   PDF (941KB) ( )   Abstract: 【Objective】Our aim is to elucidate the effects of reduced urea application combined with slow-release urea on yield and photosynthetic characteristics of rice and to lay a theoretical basis for the application of mechanical transplanting. 【Method】A split-plot design was set with 16, 18 and 20 cm plant spacing at 30 cm row spacing and four reduced urea application levels combined with slow-release urea (96 kg/hm2 of slow-release urea combined with 24 kg /hm2 of conventional urea as basal fertilizer with no top-dressing; 96 kg/hm2 of slow-release urea as basal fertilizer and 24 kg/hm2 of conventional fertilizer as top-dressing; 96 kg/hm2 of slow-release urea combined with 54 kg/hm2 of conventional urea as basal fertilizer with no top-dressing; and 96 kg/hm2 of slow-release urea combined with 30 kg/hm2 of conventional urea as basal fertilizer and 24 kg/hm2 of conventional urea as top-dressing) and Chuanguyou 7329 was used as material.【Result】 The plant spacing and reduced urea application level combined with slow-release urea showed significant or extreme significant regulating effect on leaf area index(LAI), photosynthetic characteristics and grain yield of mechanically transplanted rice in the main growing stages. The reduced urea application level combined with slow-release urea patterns played a more significant effect than the plant spacing. LAI, photosynthetic characteristics, dry matter accumulation, net photosynthetic rate and grain yield showed an increasing trend with the increase of conventional urea level combined with slow-release urea and the increase of postponed conventional urea application level under three plant spacing. At the plant space of 16 cm, the number of stem and tiller of the population increased significantly, resulting in more effective panicles, stronger competition for nutrients, weaker photosynthetic characteristics, and failure to form large panicles, although the seed setting rate was high, the grain number per panicle was low and the yield was low; Under 20 cm plant spacing, the plant density and the total number of tillers was significantly decreased, however, the lower panicle number resulted in the enhanced nutrition absorption, improved photosynthetic capability, large spike formation and increased grain number per panicle. Given the relatively low 1000-grain weight and seed setting rate, the grain yield was decreased; Under the plant spacing of 18 cm, more effective panicles were formed on the basis of sufficient tiller number of the population, which could effectively absorb nutrients in the later stage, with enhanced photosynthetic characteristics, significantly increased seed setting rate and 1000-grain weight, the correlation analysis showed that the population growth rate, photosynthetic potential and effective leaf area index at full heading stage had higher correlation with yield under reduced urea level combined with slow-release urea application and plant spacing. 【Conclusion】The treatment of 18 cm of plant spacing with 30 cm of row spacing at 96 kg/hm2 of slow-release urea combined with 30 kg/hm2 of conventional urea as basal fertilizer and 24 kg/hm2 of conventional urea as top-dressing at 4-leaf stage, it could give full play to the high yield advantage of the machine-planted indica hybrid rice in this region and improve the photosynthetic material production, with the yield up to 11 681.56 kg/hm2 was the best nitrogen application method for high yield in mechanically-transplanted rice.

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Mechanism of Exogenous Brassinolide in Alleviating High Temperature Injury at Panicle Initiation Stage in Rice Yanhua CHEN, Yaliang WANG, Defeng ZHU, Qinghua SHI, Huizhe CHEN, Jing XIANG, Yikai ZHANG, Yuping ZHANG 2019, 33(5): 457-466.  DOI: 10.16819/j.1001-7216.2019.9036 Abstract ( )   HTML ( )   PDF (1158KB) ( )   【Objective】The purpose of the study is to ascertain the effects of 2,4-epibrassinolide(EBR) application on rice panicle development and spikelet formation under high temperature, and to explore the physiological mechanism. 【Method】Heat-sensitive inbred rice cultivar IR36 was subjected to high temperature (HT, 40℃) and normal temperature (NT, 32℃) in climate chambers with EBR application, and the carbohydrate supplement, sucrose metabolism, cytokinin metabolism, and antioxidant capacity of young panicle were investigated. 【Result】1) EBR application increased the number of spikelets per panicle by 13.7% and 45.7% on average under HT and NT, respectively, in comparison to the control. And 0.15 mg/L EBR application level performed the highest efficiency in increasing the number of spikelet number, EBR application prompted panicle development and spikelet differentiation, and inhibited spikelet degeneration. 2) EBR application did not influence leaf net photosynthesis, meanwhile increased the dry matter and nonstructural carbohydrate accumulation in young panicles. Under high temperature, EBR application significantly upregulated the expression levels of sucrose transport genes OsSUT1, OsSUT2, and OsSUT4, and EBR enhanced the related enzymes activities of sucrose metabolism especially in HT than in NT. 3) EBR application reduced the expression levels of cytokinin oxidase genes, OsCKX5 and OsCKX9, under HT. Meanwhile, EBR application promoted the genes expression involved in cytokinin biosynthesis and signal transduction both under HT and NT treatments. 4) EBR application increased the activities of superoxide dismutase, catalase and peroxidase, reduced the content of superoxide under HT. 【Conclusion】Under HT conditions, EBR application at appropriate concentration could alleviate heat damage to spikelet formation by promoting carbohydrates transportation to young panicles, inhibiting cytokinin oxidation, and reducing peroxidation injures. Meanwhile, EBR application could promote spikelet formation under normal temperature.

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Laboratory Bioactivity Study on Neonicotinoid and Other Rice Paddy Used Insecticides Against the Brown Planthopper, Nilaparvata lugens(Stål) (Hemiptera: Delphacidae) Jiachun HE, Bo LI, Maocheng XIE, Fengxiang LAI, Guowen HU, Qiang FU 2019, 33(5): 467-478.  DOI: 10.16819/j.1001-7216.2019.8098 Abstract ( )   HTML ( )   PDF (2089KB) ( )   【Objective】 Bioactivity assessment of mainstream insecticides against the brown planthopper [Nilaparvata lugens(Stål)] was conducted to choose proper insecticide(s) in field conditions.【Method】We evaluated the bioactivities, short-term effectiveness, persistence of 9 neonicotinoid insecticides and other 10 commonly-used chemicals against BPH at various developmental stages by the rice stem-dipping method. 【Result】 1) Bioactivitiy: the bioactivities of the 19 insecticides differed significantly. Among them, nitenpyram, clothianidin, chlorpyrifos, sulfoxaflor, dinotefuran and cycloxaprid showed the best bioactivities to both 2nd-3rd instar and 4th-5th instar nymphs followed by pyridaphenthione, spinetoram, pymetrozine, isoprocarb and abamectin. However, insecticides such as thiamethoxam, emamectin benzoate, flonicamid only showed some bioactivities against the 2nd-3rd instar nymphs but relatively weak bioactivities against the 4th-5th instar nymphs. And other insecticides such as buprofezin, imidacloprid, thiacloprid, acetamiprid, imidaclothiz showed low bioactivities against both nymph stages. 2)Short-term effectiveness: chlorpyrifos, pyridaphenthione showed the best performance followed by isoprocarb, dinotefuran, nitenpyram, clothianidin. Pymetrozine showed the slowest effectiveness. 3)Persistence: high effectiveness levels of pymetrozine, dinotefuran, nitenpyram, clothianidin, cycloxaprid were maintained over 15 days. Pymetrozine was the best one, and there was no significant difference in the corrected mortalities of BPH reared on rice plants at 0, 5 and 10 days after pymetrozine treatment. 4)Bioactivities against adults: dinotefuran, nitenpyram, clothianidin, cycloxaprid, chlorpyrifos, isoprocarb, pymetrozine showed obvious bioactivities against adults as well as nymphs. 5)Ovicidal activity: chlorpyrifos, nitenpyram, dinotefuran and clothianidin had significant ovicidal activities. Pymetrozine, cycloxaprid, isoprocarb showed no ovicidal activity, but pymetrozine had insecticidal activity against newly hatched nymphs.【Conclusion】 As for the tested 19 insecticides, only 9 chemicals (pymetrozine, nitenpyram, dinotefuran, clothianidin, cycloxaprid, sulfoxaflor, chlorpyrifos, pyridaphenthioneand isoprocarb ) could be used to control BPH. Among them, pymetrozine had the worst short-term effectiveness and the best persistence and obvious bioactivity against different-stage BPH except eggs. Dinotefuran, nitenpyram, clothianidin and cycloxaprid showed good performance in short-term effectiveness and persistence, and the former three were effective to different stages of BPH. Sulfoxaflor had good bioactivity and short-term effectiveness, whose persistence was shorter than that of neonicotinoid insecticides. Either chlorpyrifos or pyridaphenthione could be applied alone or mixed with other insecticides to control BPH. The former one was suitable to cope with the BPH outbreak threat, because it showed the best short-term effectiveness. The bioactivity of isoprocarb was weaker than the neonicotinoids, but its short-term effectiveness was better, which could be used to mix with pymetrozine for pest control. Moreover, three insecticides such as spinetoram, abamectin, emamectin benzoate normally used to control lepidopteran pests also exerted the promising activities against BPH. However, other seven insecticides such as imidacloprid, buprofenzin and thiamethoxam were not appropriate for controlling BPH anymore.