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28 September 2018, Volume 25 Issue 5 Previous Issue    Next Issue
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Arsenic Stress Responses and Tolerance in Rice: Physiological, Cellular and Molecular Approaches Kalita Jyotirmay, Kumar Pradhan Amit, Moni Shandilya Zina, Tanti Bhaben 2018, 25(5): 235-249.  DOI: 10.1016/j.rsci.2018.06.007 Abstract ( )   HTML ( )   PDF (966KB) ( )   Arsenic (As), a potentially toxic metalloid released in the soil environment as a result of natural as well as anthropogenic processes, is subsequently taken up by crop plants. In rice grains, As has been reported in Asia, North America and Europe, suggesting a future threat to food security and crop production. As3+ by dint of its availability, mobility and phytotoxicity, is the most harmful species of As for the rice crop. Specific transporters mediate the transport of different species of As from roots to the aboveground parts of the plant body. Accumulation of As leads to toxic reactions in plants, affecting its growth and productivity. Increase in As uptake leads to oxidative stress and production of antioxidants to counteract this stress. Cultivars tolerant to As stress are efficient in antioxidant metabolism compared to sensitive ones. Iron and selenium are found to have ameliorating effect on the oxidative stress caused by As. Microbes, even many indigenous ones, in the plant rhizosphere are also capable of utilizing As in their metabolism, both independently and in association. Some of these microbes impart tolerance to As-stress in plants grown in As contaminated sites.

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Coordinated Expression of Cytosolic and Chloroplastic Glutamine Synthetase During Reproductive Stage and Its Impact in GS1 RNAi Transgenic Rice Nguyen Le Tieu-Ngoc, Lee Beomgi, Back Kyoungwhan, Soon Kim Young, Cheong Hyeonsook 2018, 25(5): 250-260.  DOI: 10.1016/j.rsci.2018.08.001 Abstract ( )   HTML ( )   PDF (1678KB) ( )   To understand the reallocation of organic nitrogen from leaf to the flower head of rice, the role of glutamine synthetase (GS) was investigated by characterizing GS1 RNAi transgenic rice, which revealed a significant reduction in panicle number and number of seeds per panicle. We observed the expression of GS isotypes at transcriptional and protein levels in flag leaves, leaf sheaths and panicles at three different flower development stages. The mRNA expression of GS1;1 was clearly suppressed in flag leaves, especially at the flowering stage. GS1 protein was barely detectable in flag leaves until the flowering stage, while GS1 protein was compromised in the leaf sheath and panicle, with transient expression of GS2 protein at the flowering stage. The glutamine level in transgenic plants was significantly reduced in both flag leaves and panicles, but ammonium was highly accumulated. The level of other amino acids, including aspartate and asparagine, tended to be higher in RNAi transgenic plants than the wild type plants during the reproductive stage. In addition, accumulation of toxic ammonium in panicles with low glutamine level might have caused low seed-setting in the transgenic rice. These results indicated that nitrogen reallocation was critical for panicle development, and that multiple GS isotypes functioned cooperatively to complete the rice life cycle when leaf nitrogen was remobilized to the developing reproductive organs.

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Determination of Heterotic Groups and Heterosis Analysis of Yield Performance in indica Rice Yingheng Wang, Qiuhua Cai, Hongguang Xie, Fangxi Wu, Ling Lian, Wei He, Liping Chen, Hua’an Xie, Jianfu Zhang 2018, 25(5): 261-269.  DOI: 10.1016/j.rsci.2018.08.002 Abstract ( )   HTML ( )   PDF (1125KB) ( )   To compare the heterosis levels among various groups of parental lines used extensively in China, identify foundational heterotic groups in parental pools and understand the relationship between genetic distance and heterosis performance, 16 parental lines with extensive genetic variation were selected from various sub-groups, and 39 hybrid combinations were generated and evaluated in Fujian and Hainan Provinces of China. The main results were as follows: (1) The 16 parental lines can be grouped into 7 sub-groups consisting of 1 maintainer sub-group and 6 restorer sub-groups; (2) Mean grain yield of the restorer lines was higher than that of the maintainer lines, and mean yield of parental lines was higher than that of the hybrid combinations; (3) The two best heterotic patterns were II-32A × G5 and II-32A × G6, moreover, the order of restorer sub-groups according to grain yield, from the highest to lowest, was G7, G6, G5, G4, G3 and G2; High specific combining ability values were observed for combinations of II-32A × G5, II-32A × G6 and Tianfeng A × G7; (4) Hybrid combinations derived from II-32A crossed with 13 restorer lines had higher yield trait values (mid-parent heterosis, better-parent heterosis, standard heterosis over check and specific combining ability) than any other combinations; (5) Genetic distance was positively correlated with panicle number, grain length and length-to-width ratio (P < 0.05) and negatively correlated with grain width, grain yield, seed-setting rate, as well as mid-parent heterosis, standard heterosis over check, and specific combining ability for grain yield (P < 0.01). These heterotic groups and patterns and their argonomic traits will provide useful information for future hybrid rice breeding programs.

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Effects of Cooking on Anthocyanin Concentration and Bioactive Antioxidant Capacity in Glutinous and Non-Glutinous Purple Rice Yamuangmorn Supaporn, Dell Bernard, Prom-u-thai Chanakan 2018, 25(5): 270-278.  DOI: 10.1016/j.rsci.2018.04.004 Abstract ( )   HTML ( )   PDF (1011KB) ( )   Purple rice is a source of bioactive antioxidants for rice consumers. Loss of the major antioxidant compounds after a range of cooking processes was evaluated by measuring the changes in anthocyanin concentration (ATC) and antioxidant capacity (DPPH activity) of four non-glutinous and four glutinous genotypes. However, soaking in water prior to cooking generally decreased more ATC and antioxidant capacity in non-glutinous than in glutinous genotypes. Wet cooking (WC) and soaking before wet cooking (S-WC) led to lose almost all the ATC and antioxidant capacity with only slight variation between genotypes. In the glutinous genotype Pieisu, which had the highest raw rice ATC, ATC remained the highest when cooked by the WC method. By contrast, almost no ATC remained after WC and S-WC in the low ATC genotypes such as Kum Doi Saket. Overall, the loss of ATC was greater in non-glutinous than in glutinous genotypes for both WC and S-WC methods, but the reverse occurred for antioxidant capacity. WC using electric rice cooker retained higher ATC than the pressure cooking. Thus, for genotypes with high ATC and antioxidant capacity, the selection of cooking method is critical for retaining and stabilizing rice quality.

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Correlation of Leaf and Root Senescence During Ripening in Dry Seeded and Transplanted Rice Hongyan Liu, Weiqin Wang, Aibin He, Lixiao Nie 2018, 25(5): 279-285.  DOI: 10.1016/j.rsci.2018.04.005 Abstract ( )   HTML ( )   PDF (1097KB) ( )   Dry seeding is a resource-saving rice establishment method. With an equivalent yield, dry seeded flooded rice (DSR) has been considered as a replacement for traditional transplanted flooded rice (TFR). However, the differences in leaf and root senescence during grain filling between DSR and TFR were seldom identified. In this study, the root length, root tip number and leaf senescence of rice varieties Huanghuazhan and Yangliangyou 6 during ripening were compared between DSR and TFR. Results showed that top three leaves in DSR had the characteristics of relatively lower SPAD value, lower N content and premature leaf senescence. In addition, both the total root length and total root tip number of DSR were significantly lower than those of TFR. In conclusion, premature and quick leaf senescence was related with inadequate root length and root tip number during ripening, which might result from the deficiency of nitrogen supply in DSR. Techniques on improving leaf nitrogen status and delaying the leaf senescence during grain-filling in DSR should be developed in future researches.

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Cultivation Systems Using Vegetation Cover Improves Sustainable Production and Nutritional Quality of New Rice for Africa in the Tropics Popice Kenmogne Nuemsi Pierre, Brice Tonfack Libert, Mbogne Taboula Judith, Ahmad Mir Bilal, Roger Baleba Mbanga Moise, Ntsomboh Ntsefong Godswill, Nono Temegne Carine, Youmbi Emmanuel 2018, 25(5): 286-292.  DOI: 10.1016/j.rsci.2018.08.003 Abstract ( )   HTML ( )   PDF (895KB) ( )   Little is known about the impact of direct sowing under vegetation cover on the production and quality of New Rice for Africa (NERICA) on poor oxisol. In this study, two NERICA varieties (NERICA 3 and NERICA 8) were grown under tropical oxisol soil with very low nutrient contents. Four cultivation systems were used in completely randomized block design, including plowing (control), unplowed soil with dead vegetation cover (DVC), unplowed soil with live vegetation cover (LVC) and unplowed soil with mixed vegetation cover (MVC). DVC significantly improved the exponential growth of NERICAs. NERICA 3 was the more productive (2.16-3.05 t/hm2) compared with NERICA 8 (0.71-1.21 t/hm2). Cultivation systems improved the nutritional quality of NERICAs. The total protein content of NERICA 3 under DVC and MVC was 84.8% and 75.0% higher than control, respectively. The total soluble carbohydrate contents of NERICA 8 under LVC and MVC was 73.2% and 57.3% higher than control, respectively. These results suggested that conservative approach like direct sowing on unplowed soil with vegetation cover systems can improve the nutritional quality of rainfed NERICAs and their sustainable production under poor oxisol soil in sub-Saharan Africa.

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Novel Sources of aus Rice for Zinc Deficiency Tolerance Identified Through Association Analysis Using High-Density SNP Array Lee Jae-Sung, Wissuwa Matthias, B. Zamora Oscar, M. Ismail Abdelbagi 2018, 25(5): 293-296.  DOI: 10.1016/j.rsci.2018.08.004 Abstract ( )   HTML ( )   PDF (966KB) ( )   Zinc (Zn) deficiency is a major soil constraint limiting rice crop growth and yield, yet the genetic control of tolerance mechanisms is still poorly understood. Here, we presented promising loci and candidate genes conferring tolerance to Zn deficiency and identified through association analysis using a 365 K single nucleotide polymorphism (SNP) marker array in a diverse aus (semi-wild type rice) panel. Tolerant accessions exhibited higher growth rate with relatively rare stress symptoms. Two loci on chromosomes 7 and 9 were strongly associated with plant vigor under Zn deficiency at a peak-stress stage. Based on previous microarray data from the same experimental plots, we highlighted four candidate genes whose expressions were accompanied by significant genotype and/or environment effects under Zn deficiency. Network-gene ontology supported known tolerance mechanisms, such as ascorbic acid pathway, and also suggested the importance of photosynthesis genes to overcome Zn deficiency symptoms.