Browsing by Author "Samarasinghe, W.L.G."

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    Phenotyping of Breeding Populations in Complement with Molecular Markers to Select Submergence Tolerant Rice (Oryza sativa)
    (Uva Wellassa University of Sri Lanka, 2013) Gunadasa, J.G.D.C.; Alwis, L.M.H.R.; Samarasinghe, W.L.G.
    Over 22 million hectares of lowland rain fed rice lands which occupy 18 % of global supply of rice are vulnerable to flash flooding worldwide and severe in Asian countries such as India, Bangladesh and Thailand. Most of these fields are cultivated with submergence tolerance landraces FR13A and FR43B with poor yield of 2 Mt/ha (Neeraja et al., 2007). As reported by the respective data sources, up to the end of January 2013, approximately 75,000 ha of paddy lands have been affected due to flood condition prevailed throughout the season. Therefore rice breeders should select the appropriate varieties for those areas with the higher yield. The study was undertaken to improve submergence tolerance in popular Sri Lankan rice variety Bg360 through identifying submergence tolerant individuals in BC2F1 population of Bg360 / Swarna Sub1 // Bg360 by phenotypic and molecular screening. Methodology This experiment was carried out in the field and laboratory at the Bio technology Division of Rice Research and Development Institute, Batalagoda which is in the Low country Intermediate Zone of Sri Lanka from May to October 2013. Two rice varieties namely Bg360 which is three and half month, submergence susceptible rice variety popularly grown in Sri Lanka, and Swarna sub1 which is a developed submergence tolerant rice variety grown in India and 526 seeds from BC2F1 population of cross of Bg360 and Swarna sub1 were grown in nursery trays for 10 days and submerged under 1 m height of water for 10 days. Number of survived plants were taken at de-submergence and number of recovered plants were numerated 14 days after de-submergence. Height difference was scored before and after submergence. A rapid DNA extraction protocol modified by Rice Research and Development Institute (RRDI), Bathalagoda was used for DNA extraction. Peatan a df DNA in she samples were confirmed by using agarose gel (1%) electrophoresis with 50 mV for 45 minutes. RM 219 microsatellite (Table 1) was used to dbtaeoa polymorphism between Bg360 and Swarna sub1. In PCR amplification, single preheat at 94 C, 35 cycles of denaturation at 94 C for 1 min, annealing at 59.1 C for 1 min and elongation for 72 C for 2 min and final extension at 72 C for 5 min were used for 15 µl of reaction volume which consist of 0.06 U Taq DNA Polymerase, 1X Buffer, 1.5 mM MgCl2, 0.1 nM dNTPs, 0.07 ϸmol forward and reverse Primers and 20 ng/µl template DNA. Agarose gel (2%) was used in 0.5X TBE buffer for electrophoresis for 2 hours under 50mV voltages to analyze the amplified DNA.
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    Quantitative Assessment of Leaf Color Change in Response to Phosphate Deficiency Tolerance in Rice
    (Uva Wellassa University of Sri Lanka, 2013) Aluwihare, Y.C.; Lelwala, R.; Ishan, M.; Sooriyapathirana, S.D.S.S.; Sirisena, D.N.; Samarasinghe, W.L.G.
    Phosphate deficiency tolerance (PDT) is one of the important traits in improving rice varieties. Annual expenditure on phosphate fertilizers for rice is Rs.1158.4 millions in Sri Lanka. Application of phosphate fertilizers also causes many other environmental and health problems (Wickramasinghe et al., 2009). If PDT rice varieties can be developed, they can be grown with reduced fertilizer applications, higher profit margin, and minimum negative effects of phosphate applications (Wissua and Ae, 2001). Because of the phosphate deficiency, the leaf color is changed. If the color differences in leaves can be quantitatively measured, it can be used to assess the PDT of different rice varieties (Fageria et al., 1988). The present study was conducted to screen selected traditional and improved rice varieties developed by Rice Research and Development Institute (RRDI), Batalagoda (Bg) for PDT using the leaf color change measurements in a quantitative approach. Methodology A total of 10 rice genotypes (nine varieties: Bg 358, H 10, H4, Bg 360, Bg 403, Bg 379-2, Bg 352, H 7 and MAS and the landrace: Suduheenati) were grown in a field at RRDI, Bathalagoda where no fertilizer has been applied for last 30 years. Plants were maintained with standard management practices except no phosphate application. The leaf color measurements; L*, a* and b* were recorded in four replicates per plant on the sixth week after planting using a spectrophotometer (CR-10, Konika Minolta, Tokyo, Japan). L* measured the darkness/lightness range of the visual color from black (-L*) to white (+L*), a* measured the range from green (-a*) to red (+a*) while b* measured the range from blue (-b*) to yellow (+b*). The quantitative estimates, C* (chroma; estimate of dullness/sharpness of the visual color) and H* (hue angle; estimate of the overall visual color) were calculated using the following equations (Melgosa, 2000).