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28 September 2014, Volume 21 Issue 5 Previous Issue    Next Issue
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Effects of Low Light on Agronomic and Physiological Characteristics of Rice Including Grain Yield and Quality LIU Qi-hua, WU Xiu, CHEN Bo-cong, MA Jia-qing, GAO Jie 2014, 21(5): 243-251.  DOI: 10.1016/S1672-6308(13)60192-4 Abstract ( )   PDF (465KB) ( )   Light intensity is one of the most important environmental factors that determine the basic characteristics of rice development. However, continuously cloudy weather or rainfall, especially during the grain-filling stage, induces a significant loss in yield and results in poor grain quality. Stress caused by low light often creates severe meteorological disasters in some rice-growing regions worldwide. This review was based on our previous research and related research regarding the effects of low light on rice growth, yield and quality as well as the formation of grain, and mainly reviewed the physiological metabolism of rice plants, including characteristics of photosynthesis, activities of antioxidant enzymes in rice leaves and key enzymes involved in starch synthesis in grains, as well as the translocations of carbohydrate and nitrogen. These characteristics include various grain yield and rice quality components (milling and appearance as well as cooking, eating and nutritional qualities) under different rates of shading imposed at the vegetative or reproductive stages of rice plants. Furthermore, we discussed why grain yield and quality are reduced under the low light environment. Next, we summarized the need for future research that emphasizes methods can effectively improve rice grain yield and quality under low light stress. These research findings can provide a beneficial reference for rice cultivation management and breeding program in low light environments.

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Allele Types of Rc Gene of Weedy Rice from Jiangsu Province, China LI Xiao-yan, QIANG Sheng, SONG Xiao-ling, CAI Kun, SUN Yi-na, SHI Zhi-hua, DAI Wei-min 2014, 21(5): 252-261.  DOI: 10.1016/S1672-6308(13)60183-3 Abstract ( )   PDF (1674KB) ( )   Weedy rice (Oryza sativa f. spontanea), the predominant type of which has a red pericarp, seriously inhibits growth and yield of direct-seeded rice in Jiangsu Province, China. In this study, we randomly selected 10 weedy rice accessions from 10 plots in Jiangsu, and then sequenced the full lengths of their Rc genes (approximately 6.4 kb). In addition, we collected 166 different full-length Rc genes in the Oryza genus from the literature and from GenBank. A collinearity sequence analysis showed that the 10 weedy rice accessions from Jiangsu all had the same wild-type allele of the Rc gene. Single nucleotide polymorphisms indicated that the nucleotide polymorphisms (π = 0.19) and the proportion of segregation sites (θw = 0.28) of the Rc genes in the 10 weedy rice accessions from Jiangsu were higher than those in 56 weedy rice accessions from USA (π = 0.09 and θw = 0.07). Haplotype and phylogenetic analyses showed that the Rc genes of weedy rice accessions from Jiangsu were not revertants of the rc gene found in Asian cultivated rice (O. sativa) varieties with white pericarp. In addition, Rc gene sequences of the rice varieties Lvdao from Lianyungang, Jiangsu and Tangdao from Anhui were more similar to those of cultivated rice than to the weedy rice from Jiangsu. These findings support the continued quarantine of weedy rice and clarify the evolutionary mechanism of the red pericarp found in the weedy rice of Jiangsu.

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Changes in DNA Methylation Pattern at Two Seedling Stages in Water Saving and Drought-Resistant Rice Variety after Drought Stress Domestication ZHENG Xiao-guo, CHEN Liang, LOU Qiao-jun, XIA Hui, LI Ming-shou, LUO Li-jun 2014, 21(5): 262-270.  DOI: 10.1016/S1672-6308(13)60194-8 Abstract ( )   PDF (1091KB) ( )   Recent studies revealed that DNA methylation plays an important role in plant growth and development. In this study, a water-saving and drought-resistant rice variety Huhan 3 was subjected to drought stress from tillering to grain-filling stages in six successive growth cycles. The variations in DNA methylation pattern between the original generation (G0) and the sixth generation (G6) were analyzed by using methylation sensitive amplification polymorphism method. The results revealed that the methylated loci accounted for 34.3% to 34.8% of the total loci. Among these methylated loci, 83.1% to 84.8% were full- and hyper-methylated and 15.2% to 16.9% were hemi-methylated. The DNA methylation level decreased from the three-leaf to four-leaf stages in Huhan 3. Differentially methylated loci (DML) between generations or/and between different developmental stages accounted for 4.0% of the total loci, most of which were only related to plant development (57.9%). Compared to G0, the DNA methylation pattern of G6 changed after drought domestication, at the three-leaf stage, de-methylation accounting for 59.1%, while at the four-leaf stage, re-methylation for 47.9%. Genome-wide alternations of DNA methylation were observed between the two seedling stages, and DML mainly occurred on the gene’s promoter and exon region. The genes related to DML involved in a wide range of functional biology and participated in many important biological processes.

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Transgene Flow from Glufosinate-Resistant Rice to Improved and Weedy Rice in China LU Yong-liang, Nilda R. BURGOS, WANG Wei-xia, YU Liu-qing 2014, 21(5): 271-281.  DOI: 10.1016/S1672-6308(13)60197-3 Abstract ( )   PDF (616KB) ( )   The development of transgenic rice with novel traits in China can increase rice productivity, but transgene flow to improved or weedy rice has become a major concern. We aimed to evaluate the potential maximum frequencies of transgene flow from glufosinate-resistant rice to improved rice cultivars and weedy rice. Treatments were arranged in randomized complete blocks with three replicates. Experiments were conducted between 2009 and 2010 at the Center for Environmental Safety Supervision and Inspection for Genetically Modified Plants, China National Rice Research Institute, Hangzhou, China. Glufosinate-resistant japonica rice 99-1 was the pollen donor. The pollen recipients were two inbred japonica rice (Chunjiang 016 and Xiushui 09), two inbred indica rice (Zhongzu 14 and Zhongzao 22), two indica hybrid rice (Zhongzheyou 1 and Guodao 1), and one weedy indica rice (Taizhou weedy rice). The offspring of recipients were planted in the field and sprayed with a commercial dose of glufosinate. Leaf tissues of survivors were analyzed by polymerase chain reaction to detect the presence of the transgene. The frequency of gene flow ranged from 0 to 0.488%. In 2009, the order of gene flow frequency was as follows: weedy rice > Chunjiang 016 > Xiushui 09 and Zhongzu 14 > Guodao 1, Zhongzheyou 1 and Zhongzao 22. Gene flow frequencies were generally higher in 2009 than in 2010, but did not differ significantly among rice materials. Gene flow frequency was the highest in weedy rice followed by the inbred japonica rice. The risk of gene flow differed significantly between years and year-to-year variance could mask risk differences among pollen recipients. Gene flow was generally lesser in taller pollen recipients than in shorter ones, but plant height only accounted for about 30% of variation in gene flow. When flowering synchrony was maximized, as in this study, low frequencies of gene flow occurred from herbicide-resistant japonica rice to other cultivars and weedy rice. Averaged across years, the risk of gene flow to weedy rice was higher than that of improved rice and hybrids. Greater resources must be dedicated to the management of remnant weedy rice in fields planted with herbicide-resistant rice, and to prevent the evolution of resistant weedy rice populations.

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Biplot Analysis of Genotype by Environment for Cooking Quality in Hybrid Rice: A Tool for Line × Tester Data Mohammad H. FOTOKIAN, Kayvan AGAHI 2014, 21(5): 282-287.  DOI: 10.1016/S1672-6308(13)60193-6 Abstract ( )   PDF (504KB) ( )   A study of combining ability for improving rice cooking quality was carried out via genotype plus genotype × environment (GGE) biplot. Four restorer lines and three male sterile lines were used to obtain F1 in a line × tester trial at the Rice Research Institute, Amol, Iran in 2009. GGE biplot analysis showed that Neda and IR56 were the best general combiners for amylose content (AC), whereas Nemat and IR28 had the highest general combining ability (GCA) effects for gelatinization temperature (GT), and IR58 and IR59 showed the highest GCA effects in terms of gel consistency (GC). Meanwhile, IR58 and IR59 showed large specific combining ability (SCA) effects for AC, while Neda and SA13 had high SCA effects for GT. Nemat and IR28 had large SCA effects for GC. Because intermediate levels of AC, GT and GC are ideal, Nemat × IR59 was considered as the best possible cross. Based on these results, the GGE biplot showed good potential for identifying suitable parents, heterotic crosses and the best hybrids in line × tester data.

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Selection of Rice Genotypes for Salinity Tolerance Through Morpho-Biochemical Assessment Md. Nasim ALI, Bhaswati GHOSH, Saikat GANTAIT, Somsubhra CHAKRABORTY 2014, 21(5): 288-298.  DOI: DOI: 10.1016/S1672-6308(13)60189-4 Abstract ( )   PDF (1449KB) ( )   The present study reported the morpho-biochemical evaluation of 15 selected rice genotypes for salt tolerance at the seedling stage. Growth parameters including shoot length, root length, plant biomass, plant turgid weight, plant dry weight along with relative water content were measured after exposure to saline solution (with electrical conductivity value of 12 dS/m). Genotypes, showing significant differential responses towards salinity in the fields, were assessed through 14 salinity-linked morpho-biochemical attributes, measured at 14 d after exposure of seedling in saline nutrient solution. Relative water content, chlorophyll a/b, peroxidase activity and plant biomass were identified as potential indicators of salt tolerance. Principal component analysis and successive Hierarchical clustering using Euclidean distance revealed that Talmugur, Gheus, Ghunsi, Langalmura, Sabitapalui, and Sholerpona were promising genotypes for further breeding programmes in rice. The maximum Euclidean distance was plotted between Thavallakanan and Talmugur (7.49), followed by Thavallakanan and Langalmura (6.82), indicating these combinations may be exploited as parental lines in hybridization programmes to develop salinity tolerant variety.

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Improving Rice-Based Cropping Pattern Through Soil Moisture and Integrated Nutrient Management in Mid-Tropical Plain Zone of Tripura, India A. K. SINGH, M. CHAKRABORTI, M. DATTA 2014, 21(5): 299-304.  DOI: 10.1016/S1672-6308(13)60190-0 Abstract ( )   PDF (567KB) ( )   An experiment was conducted in three fallow paddy fields situated on the mid-tropical plain zone of a northeastern Indian state (Tripura) to provide rice fallow management options using leftover soil moisture and nutrients. The three experimental fields were managed by growing rice under the system of rice intensification as the rainy season crop and then groundnut, lentil, rapeseed and potato as the post-rainy season crops. Fertilization under the integrated nutrient management system and lifesaving irrigation at critical stages of each post-rainy season crop were provided. Results showed that the field water use efficiency values were 5.93, 2.39, 2.37 and 59.76 kg/(hm2?mm) and that the yield of these crops increased by approximately 20%, 34%, 40% and 20% after applying two lifesaving irrigations in groundnut, lentil, rapeseed and potato, respectively. Therefore, fallow paddy field can provide possible profitable crops during the post-rainy season by utilizing the residual moisture and minimum supplemental irrigation under improved nutrient management practices.