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10 March 2019, Volume 33 Issue 2 Previous Issue    Next Issue
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Research Advances on the Low Phytic Acid Rice Breeding and Their Genetic Physiological Regulation and Environmental Adaptability Da SU, Liangquan WU, K Rasmussen Søren, Lujian ZHOU, Fangmin CHENG 2019, 33(2): 95-107.  DOI: 10.16819/j.1001-7216.2019.8083 95 Abstract ( )   HTML ( )   PDF (1073KB) ( )   Breeding variety with improved quality while maintaining or improving yields is one of the primary objectives in rice breeding. Among which, reducing the anti-nutritional factors, such as grain phytic acid content, is an effective strategy to cope with hidden hunger and increase grain bioavailabilities of zinc and iron. In this paper, we reviewed the biosynthesis of phytic acid and the genetic characteristics of related functional genes, the co-regulatory networks of phytic acid synthesis and other physiological metabolism, breeding of low phytic acid (lpa) germplasm resource and their genetic characteristics, agronomic performance and environmental ecological adaptability of lpa mutants, the possible reasons for their agronomic deterioration and ecological adaptation change, and the environmental regulation of grain phytic acid accumulation. Those contents could provide reference for production of lpa rice with suitable agronomic cultivation practices.

Research Papers

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Influence of DNA Methylation Inhibitor 5-Aza-2′-deoxycytidine on DNA Methylation and Seedling Development of Rice Hui DENG, Zhiguo E, Baixiao NIU, Lei WANG, Chen CHEN 2019, 33(2): 108-117.  DOI: 10.16819/j.1001-7216.2019.9001 Abstract ( )   HTML ( )   PDF (4873KB) ( )   【Objective】 DNA methylation is an epigenetic modification broadly existed in higher plants. DNA methylation plays an important role in regulating gene expression, maintaining the genomic stability and modulating plant development. Here, we used a DNA methylation inhibitor, 5-Aza-2′-deoxycytidine (AZA), to study how the DNA methylation status influences rice development. 【Method】We applied AZA to the rice seedlings to explore its influence on seedling development. 【Results】AZA-treatment resulted in overall hypomethylation of the rice genome. AZA-treated plants were strikingly shorter than the control, indicating AZA treatment disturbed normal development of the plants. However, the seed germination was not significantly affected. Expression of several key genes involved in DNA methylation could be repressed by AZA treatment. In addition, some genes involving defense and photosynthesis pathways were also down-regulated. 【Conclusion】Our findings confirm that AZA is a potent DNA methylation inhibitor and suggest that to maintain proper DNA methylation status is important for rice development.

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Expression of Pns6 and P8 Proteins of Rice Dwarf Virus After Virus Infecting Rice Protoplasts Jie ZHANG, Baijie WAN, Pengxiang SHANG, Xinlun DING, Zhenguo DU, Zujian WU 2019, 33(2): 118-123.  DOI: 10.16819/j.1001-7216.2019.8109 Abstract ( )   HTML ( )   PDF (886KB) ( )   【Objective】In order to clarify expression dynamics of Pns6 and P8 proteins of Rice dwarf virus after virus infecting rice protoplasts, 【Method】subcellular localization of Pns6 and P8 proteins as well as viral particles in rice protoplasts were conducted with a PEG mediated virus infecting protoplast system by immunofluorescence and electron microscope. Meanwhile, accumulation of Pns6 and P8 proteins and their RNAs in rice protoplasts were measured by Western blot and real-time fluorescence quantitative PCR. 【Result】Pns6 protein could form viroplasm-like punctate inclusion bodies in cytoplasm 48 h after virus inoculation, and P8 protein was also expressed in large quantities. Meanwhile, viral particles could form inclusion body-like structure in rice protoplasts. Expression of Pns6 and P8 proteins was both detected at 12 h after virus inoculation, and reached the maximum level after 36 h. At the same time, the expression level of Pns6 RNA peaked at 24 h and that of P8 RNA at 36 h after virus inoculation. 【Conclusion】Pns6 and P8 proteins were both expressed after virus infection, and Rice dwarf virus may also formed viroplasm-like inclusion bodies to complete virus replication and assembly in host cells.

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Identification of QTL for Panicle Traits under Multiple Environments in Rice(Oryza sativa L.) Jin LIU, Xiaoyun YAO, Dan LIU, Liqin YU, Hui LI, Qi WANG, Jiayu WANG, Maomao LI 2019, 33(2): 124-134.  DOI: 10.16819/j.1001-7216.2019.8100 Abstract ( )   HTML ( )   PDF (1490KB) ( )   【Objective】It is important to explore new panicle and grain traits QTL related to yield for further cloning and utilization of high yield genes. 【Method】A recombinant inbred line (RIL) population derived from the cross between Longdao 5 (super high-yielding japonica) and Zhongyouzao 8 (typical indica) was used to identify QTL for panicle traits in multiple environments.【Result】Sixty-three QTLs were detected on chromosomes 1, 2, 3, 4, 5, 6, 7, 8, 10 and 12. Among them, 27, 27, 18 and 35 QTLs were detected in four ecological environments, respectively. Among these QTLs, 16 QTLs were detected in two environments, 12 QTLs were detected in more than three environments, namely 25.40% and 19.05% were stably and reliably detected across multi-environments. The QTLs with pleiotropic genetic overlap effect clustered on chromosomes 1, 3, 4 and 5 were detected in multi-environments, indicating they have significant effects on panicle traits. 【Conclusion】 qSNP3 (STS3.3-STS3.6) on chromosome 3 and qSNP4.1 (RM5688-RM1359) on chromosome 4 may be two novel pleiotropic QTL clusters controlling panicle traits. In addition, epistatic effect plays an important role in the regulation of panicle traits.

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Genetic Analysis and Fine Mapping of a Major QTL for the Resistance to Southern Rice Black-Streaked Dwarf Disease Baoxuan NONG, Bixia QIN, Xiuzhong XIA, Xinghai YANG, Zongqiong ZHANG, Yu ZENG, Guofu DENG, Jianhe CAI, Zhanbiao LI, Piqing LIU, Danting LI 2019, 33(2): 135-143.  DOI: 10.16819/j.1001-7216.2019.8057 135 Abstract ( )   HTML ( )   PDF (1062KB) ( )   【Objective】Southern rice black-streaked dwarf virus(SRBSDV), which is transmitted by white-backed planthopper (Sogatella furcifera Horváth, WBPH), has caused severe yield loss in epidemic years in rice production. We analyzed the resistance mechanism of SRBSDV and identified the related gene locus by fine gene mapping to lay a scientific base for effective prevention and control of SRBSDV. 【Method】The resistance of rice material D4 against white-backed planthoppers were analyzed, and the genetic basis for the resistance to SRBSDV was analyzed by using F2 population of Guanghui 998×D4. The major QTL for resistance to SRBSDV was identified using QTL-seq, and further verified by genetic linkage analysis. 【Result】D4 was resistant to SRBSDV but not to WBPH. Genetic analysis showed that the resistance of D4 was controlled by major gene and minor genes. QTL-seq and linkage analysis revealed that the major QTL for resistance to SRBSDV in rice was located within the 1.40 M region on chromosome 9, which was termed as qSRBSDV9. Then qSRBSDV9 was fine mapped on chromosome 9 with a 102.3 kb physical distance by substitution mapping. This region contained 21 predicted genes, nine of which were related to gibberellin signaling. 【Conclusion】The results reveals the characteristics and inheritance of resistance to SRBSDV in D4. The fine mapping of qSRBSDV9 lays a base for map-based cloning and utilization.

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Identification of QTL for Grain Weight and Grain Shape Using Populations Derived from Residual Heterozygous Lines of indica Rice Andong ZHU, Zhichao SUN, Yujun ZHU, Hui ZHANG, Xiaojun NIU, Yeyang FAN, Zhenhua ZHANG, Jieyun ZHUANG 2019, 33(2): 144-151.  DOI: 10.16819/j.1001-7216.2019.8120 Abstract ( )   HTML ( )   PDF (528KB) ( )   【Objective】Grain weight and grain shape are important factors influencing grain yield and quality in rice. There are quantitative traits controlled by a large number of quantitative trait loci (QTL) that vary greatly in effect, but not much attention has been paid to minor QTL. This study was conducted to detect minor QTL for grain weight and shape in the absence of major-QTL segregation. 【Method】 Following results of a previous QTL mapping study, a residual heterozygous plant was identified from the original population. The new population derived was homozygous in regions where major QTL for grain weight and shape were detected in the previous study, but segregated in 13 segments of other genomic regions. The population was planted in Hangzhou, Zhejiang and Lingshui, Hainan. Thousand-grain weight, grain length and grain width were tested and used for QTL analysis using Windows QTL Cartographer 2.5. 【Result】A total of 22 QTL were detected, distributing on 12 intervals of 10 chromosomes. Ten of them were significant in both locations, and the other two were detected in Hangzhou only. One plant that was only heterozygous in four of the 12 QTL regions was identified, from which one new population was constructed and tested. The QTL effects of the four regions were well validated. 【Conclusion】Our results indicate that the power of detecting minor QTL could be efficiently increased by eliminating the influence of major-QTL segregation. It is also suggested that minor QTL could have a stable effect though it is believed that they are generally subjected to large influence of the genetic background and environmental conditions. Our results also lay a foundation for fine mapping, cloning and marker-assisted selection of minor QTL for grain weight and grain shape in rice.

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Analysis of Resistance to Rice Blast in indica Rice Varieties from Rice Regional Trials in the Middle and Lower Reaches of the Yangtze River in China Zhongna HAO, Xueqin MAO, Rongyao CHAI, Yanli WANG, Guochang SUN 2019, 33(2): 152-157.  DOI: 10.16819/j.1001-7216.2019.8089 Abstract ( )   HTML ( )   PDF (847KB) ( )   【Objective】Our aim is to compare the resistance to rice blast of indica rice varieties identified from rice regional trials in the middle and lower reaches of the Yangtze River in China, and analyze the characteristics of six identification plots.【Method】Eight-hundred indica rice varieties (including 111 early-season indica, 468 mid-season indica and 221 late-season indica) were tested from rice planting regions in the middle and lower reaches of Yangtze River in China since 2013 to 2017. The resistance to rice blast (leaf blast and panicle blast) of the testing varieties was identified in six experimental plots distributed respectively in Zhejiang, Hunan, Hubei, Anhui, Fujian and Jiangxi Provinces.【Result】47.5% of all the 800 rice varieties showed moderately susceptible to rice blast, followed by the moderately resistant, susceptible and highly susceptible varieties to rice blast. While only 0.2% of the varieties were resistant, and no highly resistant variety was found. The resistance composite indexes in early-, mid- and late-season varieties were 4.95, 4.85 and 4.54, respectively, indicating that all types of varieties showed moderately susceptible to rice blast. Among the six experimental plots for resistance identification, the average composite index of all varieties in Zhejiang was the lowest. In Hubei, the leaf blast was the most serious; however, the loss rate of panicle blast was the lowest. The disease grade of leaf blast in Anhui was the lowest. The incidence of panicle blast was the lowest in Fujian. In Jiangxi, the incidence and the loss rate of panicle blast, and the composite index were all the highest. According to the composite index of all varieties, the moderately susceptible varieties were the largest proportion in Zhejiang, Hunan, Hubei, Anhui and Jiangxi, however, the varieties with middle resistance were the most in Fujian. According to the disease grade for the loss rate of panicle blast, the varieties with middle resistance to panicle blast were the most in Zhejiang, Hunan and Hubei. The moderately susceptible varieties were the most in Anhui. However, in Fujian, the resistant varieties were in the largest ratio. The proportions of different types of varieties were similarly in Jiangxi. 【Conclusion】The overall levels of disease resistance in indica rice varieties from the middle and lower reaches of the Yangtze River in China was in a low level. Same varieties showed different resistance levels in different identification plots, because the six plots possibly had their own characteristics. Thus the average resistance values for the tested varieties identified in the six plots are better to fully and objectively reflect the resistance levels of new rice varieties to rice blast.

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Effect of Plant Growth Regulators on Rice Lodging Resistance and Grain Production of Main-crop and Ratooning Rice Zhenxing XIE, Junian ZHANG, Qi LIN, Feng LIU, Chuzhang ZHANG, Fangmei ZHUO, Zhaowei JIANG, Chuanying ZHUO 2019, 33(2): 158-166.  DOI: 10.16819/j.1001-7216.2019.8075 Abstract ( )   HTML ( )   PDF (1015KB) ( )   【Objective】The present study aims to evaluate the effect of plant growth regulators (PGRs) on rice lodging resistance and yield performance of ratoon rice.【Method】Jiafuzhan, Tianyouhuazhan, Yongyou 2640 were sampled with foliar application of paclobutrazol (PP333), ethephon (ETH), trinexapac-ethyl (TE) at the initial jointing stage. The culm traits, mechanical index, grain yield and yield components of main-crop and ratooning rice were investigated.【Result】Yongyou 2640 had the strongest breaking resistance, plant thrust resistance and lodging resistance; Jiafuzhan had the longest internodes, the highest plant height, the maximum lodging index and the weakest lodging resistance among the three varieties while the lodging resistance of Tianyouhuazhan was between them. Compared with foliar application of water (control), application of PP333 had no marked effect on internode length, plant height, culm wall thickness, but increased culm diameter of the 3rd internode (from the top), enhanced breaking resistance of the 4th (from the top) and the 3rd internodes, drove down lodging index of the 4th and 3rd internodes; application of ETH increased length of the 4th internode, culm diameter of the 3rd internode and plant height, but had no obvious effect on culm wall thickness, reduced lodging index of the 3rd internode; application of TE shortened length of the 4th and the 2nd (from the top) internodes and plant height, increased culm diameter of the 3rd internode and culm wall thickness of the 3rd and the 2nd internodes, strengthened breaking resistance of the 4th and the 3rd internodes, reduced lodging index. PP333, TE decreased the grain production of main-crop but increased ratooning rice, while ETH decreased both main-crop and ratooning rice. Total grain production of Tianyouhuazhan and Yongyou 2640 was reduced by PGRs treatments, total yield of Jiafuzhan was increased by PP333 and TE application while decreased by ETH.【Conclusion】Comprehensively, application of TE enhanced the plant lodging resistance without negative effect on total yield of ratooning rice, and thus it could be used as a practice to prevent lodging in rice production.

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Correlation Between Root Morphology and Accumulation of Phosphorus in Rice Seedlings under Different N Forms Chen CHEN, Haiqing GONG, Mengcan JIN, Hongjian GAO 2019, 33(2): 167-175.  DOI: 10.16819/j.1001-7216.2019.8059 168 Abstract ( )   HTML ( )   PDF (1297KB) ( )   【Objective】Plant root morphology has certain plasticity for adapting to low phosphorus stress, and is of great significance for improving phosphorus absorption and utilization. Therefore, we used 102 major rice varieties in the middle and lower reaches of the Yangtze River as the tested materials to study the correlation between root morphology and phosphorus uptake of rice seedlings. 【Method】Hydroponic experiments were conducted to investigate the influences of NH4+-N and NO3--N at the same concentration (40 mg∙L-1) on dry weight, P concentrations and contents as well as the root morphology.【Result】At the six-leaf stage of rice incubated under the same concentration of nitrogen, the average biomass of the rice seedlings amounted to 67.87 mg per plant in the NH4+-N solution, 4.27 mg higher than that in the NO3–-N solution. The average P content was 0.49% when grown in the NH4+-N solution, 0.10% higher than that of rice seedlings grown in the NO3–-N solution. In addition, the average accumulation of P in the seedlings was 0.37 mg per plant when supplied with NH4+-N, 0.10 mg higher than that supplied with NO3–-N. The coefficient of variation of root morphological indexes were in the order of the number of tips > total root length > the number of branches > total root area > the number of crossing > the total root volume > average diameter in the NH4+-N solution; the coefficient of variation of root morphological indexes were in the order of the number of tips > the number of branches > total root length > total root area > the number of crossing > the total root volume > average diameter in the NO3–-N solution. The total root length, total root area, branching number and crossing number were significantly correlated with biomass, P content, and P accumulation in rice plants in the NH4+-N solution; whereas the total root length, total root area, tip number and crossing number were significantly correlated with biomass, P content, and P accumulation in rice plants in the NO3–-N solution.【Conclusion】The correlations between P uptake and the indices of root morphology when plants were supplied with NH4+-N were higher than those supplied only with NO3–-N. The total root length, total root area and crossing number might be important indicators for evaluating the P use efficiency of rice at seedling stage.

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Genetic Diversity and Pathogenicity Differentiation of Rhizoctonia solani AG-1 IA from South China Crop Breeding Area in Hainan Province Minghai ZHU, Dandan PENG, Canwei SHU, Erxun ZHOU 2019, 33(2): 176-185.  DOI: 10.16819/j.1001-7216.2019.8048 Abstract ( )   HTML ( )   PDF (939KB) ( )   【Objective】In order to clarify the genetic differentiation and the correlation between genetic diversity and pathogenicity of Rhizoctonia solani AG-1 ⅠA in South China Crop Breeding Area, the genetic diversity, population genetic structure, pathogenicity and the correlation between genetic diversity and pathogenicity of 60 R. solani AG-1 IA isolates collected from the core region (Sanya, Ledong and Lingshui) and non-core region (Qiongzhong, Tunchang and Ding’an) of South China Crop Breeding Area were comparatively analyzed 【Method】by using AFLP molecular marker technique and detached leaf inoculation method. 【Result】The cluster analysis results showed that the genetic diversity of R. solani AG-1 ⅠA in the core region was relatively higher. The analysis results of population genetic structure showed that the percentage of polymorphic loci (PPL), Nei’s gene diversity index (H), Shannon’s information index (I) and gene flow (Nm) in the core population were 82.24%, 0.1932, 0.3062 and 2.5627, respectively, higher than those of non-core population with PPL, H, I and Nm being 67.49%, 0.1535, 0.2447 and 0.9365, respectively. However, the genetic differentiation coefficient (Gst) in the core population was 0.1633, lower than that of non-core population whose Gst was 0.3481. 【Conclusion】These results showed that the degree of genetic variation of the isolates from core region was higher than that of the isolates from non-core region. Much gene flow among the core populations and little gene flow among the non-core populations existed, but the genetic variation of both regions was mainly within the population. Overall, the degree of genetic differentiation in the isolates of core region was higher. The results of pathogenicity and correlation between genetic diversity and pathogenicity showed that most isolates from core region belonged to the medium pathotypes and most isolates from non-core region belonged to the medium or strong pathotypes, but there was no correlation between pathogenicity and AFLP lineage.

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Effects of Nystatin Treatment on Detoxification Enzymes and Uricase Content in Nymphs of the Brown Planthopper [Nilaparvata lugens (Stål)] Juefeng ZHANG, Fang LI, Haiying ZHONG, Jianming CHEN 2019, 33(2): 186-190.  DOI: 10.16819/j.1001-7216.2019.7129 Abstract ( )   HTML ( )   PDF (849KB) ( )   【Objective】To illuminate the effect of concentrations of nystatin on physiological indicators of brown planthoppers [Nilaparvata lugens (Stål)],【Method】detoxifying enzymes and uricase gene relative transcriptional level in brown planthoppers (Nilaparvata lugens) were measured after treatment with different concentrations of nystatin. 【Result】The content of aromatic amidase (AAD) in the brown planthopper(BPH) population fed on nystatin treated rice was decreased in the early stage, and increased gradually in the late stage. Nystatin treatment could significantly decrease the content of O-deethyl enzyme (ODEE). Activity of carboxylesterase(CarE) and glutathione S-transferase(GST) in BPH showed different trends under the treatment of nystatin. The activities of CarE and GST in 600 U/mL nystatin treated BPH population was induced-inhibited-induced during the treatment period, while there has been general uptrend of activities of two enzymes in the 300 U/mL and 150 U/mL nystatin treated populations within 72 h. The relative transcriptional level of uricase gene in different concentrations nystatin treated BPH populations had no significant difference with control by treatment with 24 h and 48 h. After feeding 48 h, the transcriptional level in three nystatin treated BPH populations and control population all decreased. To 72 h, the relative transcriptional level of uricase gene increased and transcriptional level in treated population was significantly lower than that in control population. 【Conclusion】Four detoxifying enzymes showed different trends after BPH was fed on rice treated with nystatin at different concentrations, nystatin treatment also reduce the content of uricase by reducing the number of yeast-like symbiotes.