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10 July 2020, Volume 34 Issue 4 Previous Issue    Next Issue
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Reviews and Special Topics

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A Review on How Plant Hormones and Environment Factors Are Involved in Rice Root Hair Development Bin LI, Jin HUANG, Li WANG, Jin LI, Yueyang LIANG, Ji CHEN 2020, 34(4): 287-299.  DOI: 10.16819/j.1001-7216.2020.9138 Abstract ( )   HTML ( )   PDF (866KB) ( )   Plant root hairs are important structures on the root surface for absorption of water, inorganic and organic nutrients. The root hairs which are regulated by both genetic and environmental factors, also play important roles when plants are dealing with environmental stress conditions. In this review, we analyzed how stress such as P deficiency, genetic factors and the core regulatory network composed of ABA,ETH, ABA work together during the regulation of rice root hair development. At last, we come up with issues which remains unclear but are critical and could be potential research focus.

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Application of Phenomics in Rice Research Yongbin PENG, Xianzhi XIE 2020, 34(4): 300-306.  DOI: 10.16819/j.1001-7216.2020.9083 Abstract ( )   HTML ( )   PDF (381KB) ( )   As the staple crop throughout the world, rice functional genomic research for the important agronomic traits is a hotspot in plant biology research area. The genotype, phenotype, and environmental factors are three critical components of the genetic research in plant. The development of high-throughput sequencing technology makes plant genotyping easier. However, phenomics research has trailed the genotype research. Being labor-intensive, high-cost, and susceptible to artificial subjectivity, the conventional phenotyping techniques could not obtain adequate genetic information. Phenomics technique, which is non-invasive and high-throughput to obtain accurate phenotypes, plays a key role in solving the above problems existing in traditional phenotyping techniques. In this review, the application of plant phenomics in rice research is summarized, which provides theoretical support for the modern rice research methods that combines genomics with phenomics.

Research Papers

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Physiological Characters and Gene Mapping of a Yellow Leaf and Early-senescence Mutant osyes1 in Rice Fudeng HUANG, Chaoyue ZHAO, Xin WU, Huanhuan HE, Fangmin CHENG, Chunshou LI, Gang PAN 2020, 34(4): 307-315.  DOI: 10.16819/j.1001-7216.2020.0301 Abstract ( )   HTML ( )   PDF (3109KB) ( )   【Objective】Leaf is a main photosynthetic organ and its color mutants of rice are ideal materials for the study of photosynthesis, chlorophyll biosynthesis and metabolism, and chloroplast development in plants. 【Method】The mutant osyes1 (Oryza sativa yellow-leaf and early senescence 1) was obtained through 60Co γ-radiation treatment of indica cultivar Zixuan 1. The seedlings of osyes1 and its wild type were treated with exogenous H2O2. The SOD and CAT activities, ROS level, MDA content, soluble protein contents, chlorophyll contents, the net photosynthetic rate and chloroplast ultrastructure were analyzed for osyes1 and its wild type leaves at heading stage. The main agronomic traits of osyes1 and its wild type plants were analyzed under field conditions at maturation stage in Hangzhou. The recessive individuals in F2 population derived from osyes1/02428 were used to locate the gene by the map cloning method.【Results】The yellow-leaf and early-senescence symptoms started at 3- or 4-leaf stage, and gradually spread to all of the leaves after heading. Due to the early-senescence of the leaves of the mutant osyes1, its major agronomic traits including plant height, panicle length, grain number per panicle and the seed setting rate were markedly reduced. Moreover, the mutant osyes1 exhibited hyper-sensitivity to exogenous H2O2. The physiological analysis indicated that the contents of chlorophyll and the activities POD and CAT in the third-top leaf was significantly lower than those in the flag leaf and the second-top leaf in wild-type (WT) plants, but all of them in the mutant plants were significantly lower than those in its WT. Compared with the WT plants, the contents of MDA, H2O2 and O2- followed a steady increasing trend in the flag, second-top and third-top leaves of the mutant, while their soluble protein levels were progressively dropping. Genetic analysis confirmed that osyes1 was controlled by a single recessive nuclear gene, which was mapped to a region of 708 kb flanked by two SSR markers (RM21353 and RM21384) on the short arm of chromosome 7. 【Conclusion】In this work, the main agricultural traits were significantly reduced in osyes1 for the yellow leaf and early senescence. OsYES1 was located in a 708 kb range between RM21353 and RM21384 by map-based cloning strategy.

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Development and Utilization of Functional Markers for Imidazolinone Herbicides Resistance Gene in japonica Rice Variety Jinjing 818 Guangda WANG, Peng GAO, Wenyan YANG, Ao CUI, Jianhua ZHAO, Zhiming FENG, Wenlei CAO, Zongxiang CHEN, Shimin ZUO 2020, 34(4): 316-324.  DOI: 10.16819/j.1001-7216.2020.9134 Abstract ( )   HTML ( )   PDF (4466KB) ( )   【Objective】Cultivating herbicide resistant rice varieties is an important direction in rice breeding. Developing efficient functional markers can accelerate the screening of herbicide resistance trait. 【Method】dCAPS and KASP techniques were used to analyze the genotypes of the experimental materials. In addition, the phenotypes were identified by herbicide spraying test. 【Result】Through sequence alignment analysis, we further confirmed that the mutation of 627 amino acid of acetolactate synthase (ALS) gene from serine (S) into asparagine (N) in Jinjing 818 (here after named ALS627N) produces strong resistance to imidazolinone herbicides. According to the DNA sequence flanking the mutation site, we developed two novel functional markers, dC-ALS-627 and K-ALS-627, for detecting this resistant allele ALS627N. The two markers can effectively distinguish homozygous ALS627N type, heterozygous type and homozygous wild type. Combined with herbicide spraying test, we confirmed that ALS627N is a dominant herbicide resistant gene. 【Conclusion】 We validated that the two markers have great potential in marker-assisted breeding for ALS627N gene. Totally, this study will accelerate the development of new varieties with resistance to imidazolinone herbicides, and have significance in breeding practice.

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Genome-wide Association Analysis of Rice Heading Date and Yield-related Traits Based on MAGIC Population Xiucai WEI, Jindong LIU, Licheng LIU, Yongchao LI, Xiaowu PAN, Zheng DONG, Wenqiang LIU, Haibo XIONG, Jun MIN, Xiaoxiang LI 2020, 34(4): 325-331.  DOI: 10.16819/j.1001-7216.2020.0107 Abstract ( )   HTML ( )   PDF (382KB) ( )   【Objective】The objective of the study is to identify new genes related to heading date and yield related traits in rice, and to screen the elite rice lines carrying favorable alleles, therefore providing new genes and excellent germplasm for molecular marker-assisted (MAS) breeding.【Method】The multi-parent generation inter-crosses (MAGIC) population MAGIC-Hei was planted in 2017 and 2018 in Changsha, Hunan Province. Genome-wide association analysis was performed to detect the quantitative trait loci associated with heading date, number of tillers per plant, grain number per panicle, seed setting rate, 1000-grain weight and grain yield per plant based on genotyping by sequencing (GBS).【Results】Totally, 26 QTLs that control heading date and yield related traits were identified on all the chromosomes except chromosome 10 in the two years. Of these, 11 are new and qNTP9, associated with the number of effective panicles, was detected in the two years. qNTP9 was less affected by environment and could be used for further fine mapping and gene cloning. Based on the phenotypic and the SNP genotypes five elite lines carrying favorable alleles were selected, which could be used for future high-yielding rice breeding. 【Conclusion】The loci associated with heading date and yield related traits could be used for rice breeding.

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Characteristics of Seedling Raising and Mechanized Transplanting of Hybrid Rice with a Low Seeding Rate by Precise Seeding Method Yaliang WANG, Defeng ZHU, Jing XIANG, Huizhe CHEN, Yuping ZHANG, Yicheng XU, Yikai ZHANG 2020, 34(4): 332-338.  DOI: 10.16819/j.1001-7216.2020.9113 Abstract ( )   HTML ( )   PDF (1307KB) ( )   【Objective】 The purpose of the study is to ascertain the effect of precise hill-sowing and drill-sowing methods on seedling raising and the characteristics of mechanized transplanting of hybrid rice with a low seed sowing rate below 70 g, and to further break the current technical bottleneck in mechanized transplanting process of hybrid rice. 【Method】 In this study, Zhongzheyou 1 and Yongyou 1540 were mechanically hill-sowed and drill-sowed in standard seedling raising trays with mechanized broadcasting as the control. The hill-sowing specification was 16×34 hill, and 16 drills were set in longitudinal direction for drill sowing. The seed sowing rates were 5 seeds, 3 seeds, and 2 seeds per hill for hill sowing, and the same seed rates were set in drill sowing. The effects of different sowing methods on the growth of seedlings and their mechanical transplanting characteristics were investigated. 【Results】 1) Sowing methods presented no significant effect on seedling percentage with a reduction in seeding rate. 2) A reduction in seeding rate improved rice seedling consistency, especially in hill sowing and drill sowing as compared with broadcasting. 3) In comparison with seed broadcasting, under hill seeding and drill seeding, seedling roots were more entwined as seedling mats. Under hill-sowing and drill sowing, Zhongzheyou 1 and Yongyou 1540 had 75.4% and 81.0% higher intertwining force than that of broadcasting, respectively. Precise hill- and drill-sowing generated effective seedling blanket without significant difference between the two treatments, while broadcast sowing did not. 4) Hill sowing and drill sowing significantly reduced the missed hill percent of machine transplanting. The missed hill percent of Zhongzheyou 1 and Yongyou 1540 under hill sowing and drill sowing were 76.3% and 74.6% lower than that of broadcast sowing in average, respectively. The missed hill percent for hill-seeding and drill-seeding with 3 seeds per hill was below 1%, 10% lower than that of broadcast sowing. 5) The uniformity of machine-transplanted seedling under hill sowing and drill sowing were better than that of broadcast sowing. And the proportion of the treatments with expected seedling-catching number in mechanized transplanting (2 to 5 seedlings with 5 seeds per hill, 1 to 3 seedlings with 3 seeds per hill and 1 to 2 seedlings with 2 seeds per hill) for the two cultivars were all above 80% in hill-sowing and drill-sowing in combination with machine transplanting, and the seedling uniformity of machine-transplanted Zhongzheyou 1 and Yongyou 1540 was 121.2% and 67.0% higher than that under broadcast sowing. Meanwhile hill sowing had a better result than drill sowing. 【Conclusion】 Precision hill seeding and drill seeding provide an alternative measure to current problems such as large amount of seeds, high missed hill percent and uneven seedling taking in the process of machine transplanting of rice.

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Effects of Irrigation and Fertilization Coupling on Biological Characteristics, Water and Nitrogen Use Efficiencies of Rice in Cold Regions Under Leaf Age Regulation Fei XU, Wenzhi SUI, Tuo ZHANG, Baodong HUAI, Xue YANG 2020, 34(4): 339-347.  DOI: 10.16819/j.1001-7216.2020.9102 Abstract ( )   HTML ( )   PDF (479KB) ( )   【Objective】The objective is to improve the growth and development of rice by optimizing water and fertilizer supply in rice growing duration.【Method】A field experiment of fertilization and irrigation under leaf age regulation was conducted in 2016 and 2017 at 852 Farm in Heilongjiang Province. Rice variety Kendao 24 was used as material under two irrigation modes (leaf age irrigation mode, LI; conventional irrigation mode, RI) and two fertilization modes (leaf age regulation side deep fertilization mode, SF; conventional fertilization mode, RF).【Result】Rice morphological traits, photosynthetic characteristics, water and fertilizer use efficiency and grain yield were significantly affected by LI+SF (P< 0.05). Compared with RI + RF, LI+SF significantly increased leaf area index, adventitious root number per plant, total root length, total root surface area and total root volume by 21.2%, 22.7%, 20.8%, 45.2% and 17.8%, respectively. Photosynthetic rate, net photosynthetic rate, chlorophyll contents and stomatal conductance were significantly increased by 17.4%, 18.4%, 26.8% and 40.1%, respectively. Seed setting rate, 1000-grain weight and theoretical yield were significantly increased by 6.3%, 2.4% and 28.2%, respectively. Average yield was increased by 5.2%, and net income was increased by 13.21%. Agronomic efficiency of nitrogen fertilizer, grain nitrogen uptake, grain yield and utilization efficiency, partial productivity of nitrogen fertilizer and nitrogen harvest index were significantly increased by 11.1%, 6.9%, 5.8%, 13.6% and 8.0%, respectively. In addition, 1 000 t/hm2 irrigation water can be saved by LI mode. RI+SF mode can exert a positive influence on plant morphology, photosynthetic characteristics, biological yield and water and fertilizer use efficiency. The average yield was increased by 2.3%. However, the coupling effect of water and fertilizer was not fully exerted.【Conclusion】LI + SF mode is the best precise irrigation and fertilization mode in this study, and it is also suitable to be popularized as a water-saving, fertilizer saving and high-yield technology for rice in the cold area of northern China.

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Response of Yield Traits of Rice (Ⅱ-You 898) to Abrupt Drought-flood Alternation Yun GAO, Tiesong HU, Xuebin QI, Hongwei YUAN 2020, 34(4): 348-358.  DOI: 10.16819/j.1001-7216.2020.0103 Abstract ( )   HTML ( )   PDF (6044KB) ( )   【Objective】Abnormal global climate change leads to the reoccurrence of abrupt drought-flood alternation (ADFA). In order to national food security and disaster prevention and reduction in crops, we analyzed yield response characteristics of rice to ADFA. 【Method】The experiment was conducted at the Xin-maqiao irrigation experimental station at the Anhui and Huaihe River Institute of Hydraulic Research in China (117°22′E, 33°09′N) between 2017 and 2018. Three drought-flood alternation treatments were designed and compared with normal irrigation conditions. Based on the experimental data, the effects of drought, flood, and ADFA on rice yield and yield components were analyzed, the quantitative indicator R for the compensation or reduction of the early drought and later floods was proposed, and the interaction effects between late flooding stress and early drought stress on yield was revealed.【Result】Compared with the normal group, ADFA stress reduced the rice yield. The yield reduction ranged from 12.38% to 56.15%. Among them, the combination of heavy drought and heavy flood was the most unfavorable for yield. The reduction in the grain number and the grain weight was the main reason for yield reduction under ADFA stress. The drought stress of the ADFA groups compensated the yield under flood conditions, mainly because the grain number per panicle, total grain number and seed setting rate increased during the drought period. The flood stress of the ADFA groups reduced the yield under drought conditions, and the decrease in the grain number per panicle, total grain number, thousand-seed weight and seed setting rate during the flooding period was the main reason. 【Conclusion】The results show that in the case of light and moderate drought stress occurring at the early stage, the damage caused by late-stage flood stress on rice should be avoided as possible; if flooding is predicted to occur in the later period and the drainage facilities can not eliminate its adverse effects, drought treatment can be carried out in advance at the medium-late period of the jointing stage to reduce the loss of rice yield.

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Difference of Metabolites in Brown Rice Between Liaojing 433 and Koshihikari with Good Eating Quality Feng SHEN, Hongbo JIANG, Bo LIU, Xiuru ZHANG, Jun LIU, Wenxiao XIE, Jipan YAO, Liang MA 2020, 34(4): 359-367.  DOI: 10.16819/j.1001-7216.2020.9116 Abstract ( )   HTML ( )   PDF (1428KB) ( )   【Objective】Our goal is to analyze the metabolite difference between good eating-quality japonica rice Liaojing 433 and Koshihikari, and provide reference for breeding good eating-quality rice. 【Method】 GC-MS was used to detect metabolites in brown rice of Liaojing 433 and Koshihikari. Online software was used to analyze metabolic spectrum and metabolic pathway differences. 【Result】 233 metabolites were identified in both cultivars by GC-MS, among which 158 in Liaojing 433 have higher contents than in Koshihikari, accounting for 67.81% of the total. PCA and PLS-DA analysis found that there were different metabolic profiles between Liaojing 433 and Koshihikari with significant differences in contents of 64 metabolites. Among different metabolites, 42 metabolites had relative high contents in Liaojing 433. Glucosamine acid, trisaccharide, cellobiose, 4-aminobutyric acid, oleic acid, α-tocopherol, pantothenic acid, inositol, quinic acid and chlorogenic acid of Liaojing 433 were 23.86, 13.35, 2.53, 2.44, 9.32, 2.66, 2.90, 3.54, 4.05 and 2.10 times as many as those in Koshihikari, respectively. There are 22 kinds of relative high contents in brown rice in Koshihikari, and the nutrition-related arabinol, linoleic acid, ferulic acid and inositol-4-phosphoric acid are 1.61, 2.33, 1.39 and 2.39 times as many of those in Liaojing 433. Between Liaojing 433 and Koshihikari, there were significant differences in 11 metabolic pathways. The relative contents of metabolites detected by inositol phosphate metabolism, ascorbic acid and aldehyde acid metabolism, tyrosine metabolism and phenylpropane biosynthesis of Liaojing 433 were all higher than those of Koshihikari. 【Conclusion】 The metabolite composition of Liaojing 433 and Koshihikari brown rice was significantly different. Compared with Koshihikari, Liaojing 433 has a good taste and high dietary fiber content. In addition, Liaojing 433 has stronger health care function and antioxidant capacity. GC-MS metabolomics analysis method is a powerful tool for analyzing nutritional differences among rice varieties.

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Effector XopN of Xanthomonas oryzae pv. oryzae Plays a Virulent Role in Rice Varieties Harboring OsSWEET11 Homologs Li LI, Xuyan MO, Tiantian LI, Liyuan ZHANG, Hansong DONG 2020, 34(4): 368-382.  DOI: 10.16819/j.1001-7216.2020.9108 Abstract ( )   HTML ( )   PDF (2850KB) ( )   【Objective】 Xanthomonas outer proteins (Xops) are conservatively virulent effectors or virulence-assistant components secreted by the type Ⅲ secretion system in plant-pathogenic bacteria that falls into the Xanthomonas genus, including the rice bacterial blight pathogen. Xops were secreted to the outside of bacterial cells, and then transported to plant cells to play a pathological role. One of these proteins, XopN, secreted by the standard strain PXO99A of the rice pathogen, has been implicated in the bacterial virulence by subverting plant immunity, but the specificity in the virulence role of XopN is unclear. 【Method】 By using the double crossover homologous-recombination technique, the XopN gene-knockout mutant ∆XopN and genetically complemented strain ∆XopN/XopN were generated under the background of the bacterial wild-type strain PXO99A. By comparing both recombinant strains with PXO99A in terms of bacterial multiplication in nutrition broth, the role of XopN in the bacterial multiplication was evaluated. Based on literatures, 14 varieties of rice were chosen for experimental assessments on the contribution of XopN to the spectrum of the bacterial virulence. By quantitative analyses of gene expression, the virulence of XopN was related to the effects of bacterial infection on foliar expression of the OsSWEET11 gene or its homologs in different rice varieties. 【Result】 The bacteria gain better multiplication in the medium with the presence of the XopN gene, in contrast to the gene-knockout mutation, which highly impairs the bacterial propagation level. Based on bacterial populations of PXO99A, ∆XopN and ∆XopN/XopN multiplied in rice leaves, as well as severities of subsequently developed leaf blight symptoms, the 14 rice varieties fall into two categories. 1) Ten of the rice varieties (IRBB1, IRBB3, IRBB8, IRBB10, IRBB14, IR24, IRBB203, IRBB204, IRBB205 and IRBB211) display similar susceptibility to the bacteria no matter whether the XopN gene is present or not. 2)By contrast, the bacteria depend on XopN to cause strong virulence on rice varieties IRBB208, Asominori and Nipponbare. The bacteria also depend on XopN to perform a relatively low level of virulence on the rice variety IRBB13. In IRBB13 leaves, the virulence role of XopN is coincident with a marked suppression of the recessive resistance gene OsSWEET11/xa13 by the bacterial infection. On the contrary, the bacterial infection causes enhanced expression of the dominant disease-susceptibility gene OsSWEET11/Xa13 in leaves of Nipponbare and enhanced expression of the gene homologs in IRBB208 and Asominori leaves. In essence, the transcriptional promotion or inhibition of the OsSWEET11 homologs is provided by the bacterial strains PXO99A and ∆XopN/XopN, instead of ∆XopN, suggesting the critical role of XopN in inducing the gene expression. In addition, XopN is also required for the bacteria to effectively induce hypersensitive response in leaves of the non-host plant tobacco. While a high extent of the hypersensitive response is induced by PXO99A or ∆XopN/XopN strain, the response incurs a substantial reduction by ∆XopN. 【Conclusion】 XopN is a multifunctional effector and plays a virulence role in rice varieties that possess OsSWEET11 or its homologs. XopN is also necessary to the bacterial multiplication and has an additive contribution to the induction of hypersensitive response by the bacteria in a non-host plant.