Rice Research and Development Institute

Rice, Sri Lanka

Rice Research and Development Institute

Rice, Sri Lanka

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Somaweera K.A.T.N.,University of Peradeniya | Suriyagoda L.D.B.,University of Peradeniya | Suriyagoda L.D.B.,University of Western Australia | Sirisena D.N.,Rice Research and Development Institute | De Costa W.A.J.M.,University of Peradeniya
Plant and Soil | Year: 2016

Background and aims: Knowledge on periodic uptake, accumulation and allocation of nitrogen (N), phosphorus (P) and potassium (K) in different tissues of a rice plant under different soil moisture management conditions is important when implementing efficient and effective water management practices ensuring sustainable rice production. Methods: Rice variety Bg358 was grown in soil columns containing sufficient amounts of N, P and K. Four water management treatments were used; (i) continuous flooding (CF) of soil from crop establishment to maturity, (ii) CF until tillering (4 weeks) and Alternative Wetting and Drying (AWD4) thereafter, (iii) CF until flowering (10 weeks) and AWD thereafter (AWD10), (iv) CF until flowering and Top Soil Drying (TSD) thereafter (TSD10). Harvests were made in 2 weeks intervals. Key results: Root growth of AWD4 decreased from 4th week compared with CF, and then enhanced from flowering onwards; thereby developing more roots in the top 20 cm soil layer increasing the root mass ratio. Both N and K uptake continued until maturity while P uptake continued until 2 weeks before maturity, and the amount taken up was highest for K and lowest for P. Moisture limitations substantially reduced tissue P content and retranslocation of P to panicles while the lowest reductions were observed in N. Therefore, internal utilisation was most efficient for P and lowest for N i.e., during grain filling N resorbed only from flag leaves, K from green, dead and flag leaves and only in AWD4, and P from green, flag and dead leaves, and stems. Conclusion: Initially reduced root growth under AWD stimulated after flowering. Soil moisture limitation reduced P uptake greatly and thus had most efficient internal P utilisation mechanisms throughout the life cycle while those of N were the lowest. © 2015, Springer International Publishing Switzerland.


Anputhas M.,Okanagan University College | Samita S.,University of Peradeniya | de Abeysiriwardena S.Z.D.,Rice Research and Development Institute
Communications in Biometry and Crop Science | Year: 2011

Identification of rice varieties with wider adaptability and stability are the important aspects in varietal recommendation to achieve better economic benefits for farmers. Multi locational trails are conducted in different locations/seasons to test and identify the consistently performing varieties in wider environments and location specific high performing varieties. The interaction aspect of varieties with environment is complex and highly variable across locations. Thus, the identifying varieties under these circumstances are difficult for varietal recommendations. However, several methods have been proposed in the recent past with the complex computation requirements. But, the aid of statistical software and other programs capabilities ease the complexity to a large extent. In this study, we employed one of the established techniques called variance component analysis (VCA) to make the varietal recommendation for wider adaptability for many varying environments and the location specific recommendations. In this method variety × environment interaction is portioned into components for individual varieties using yield deviation approach. The average effect of variety (environment centered yield deviation - D k) and the stability measure of each variety (variety interaction variance - s k 2) are used make the recommendations. The rice yield data of cultivars of three month maturity duration, cultivated across diverse environments during the 2002/03 wet-season in Sri Lanka was analyzed for making recommendations. Based on the results the variety At581 gave the highest D k value with wide adaptability selected for general recommendation. Varieties Bg305 and At303 also had relatively higher D k and thus these two can also be selected for general cultivation purpose. © CBCS 2011.


Chauhan B.S.,International Rice Research Institute | Abeysekara A.S.K.,Rice Research and Development Institute | Kulatunga S.D.,Rice Research and Development Institute | Wickrama U.B.,Rice Research and Development Institute
Weed Technology | Year: 2013

Dry-seeded rice systems are an emerging production technology in many Asian countries. A field study was conducted in 2011 and 2012 at the farm of the Rice Research and Development Institute, Batalagoda, Sri Lanka, to evaluate the performance of different herbicides in a dry-seeded rice system. Weed control treatments were nontreated (weedy), pretilachlor plus pyribenzoxim, cyhalofop-butyl, thiobencarb plus propanil, propanil, and bispyribac-sodium plus metamifop. All these POST herbicides were applied at 8 d after sowing, followed by an MCPA spray at 20 d after sowing. The dominant weeds in the study were barnyardgrass, Chinese sprangletop, and knotgrass. All herbicide treatments provided similar weed control, which ranged from 82 to 99%. Weeds in the nontreated plots reduced rice grain yield by 58 to 79% compared with the herbicide-treated plots. All herbicide-treated plots, except cyhalofop-butyl-treated ones, produced similar grain yield, which ranged from 3.7 to 4.2 t ha-1 in 2011 and from 6.0 to 7.0 t ha-1 in 2012. The results of our study suggest that different herbicides provided similar weed control and therefore different herbicides can be rotated in different seasons to reduce selection pressure on weeds.


Chauhan B.S.,International Rice Research Institute | Abeysekera A.S.K.,Rice Research and Development Institute | Wickramarathe M.S.,Rice Research and Development Institute | Kulatunga S.D.,Rice Research and Development Institute | Wickrama U.B.,Rice Research and Development Institute
Crop Protection | Year: 2014

Weedy rice is a great threat to rice production in Sri Lanka. Selective herbicides to manage weedy rice in conventional rice cultivars are not available in Sri Lanka. In the absence of appropriate chemical control measures, cultural approaches may help to achieve effective control of weedy rice. A study was conducted in two consecutive seasons in farmers' fields at three sites (Atalla, Samanthurai, and Girithale villages) in Sri Lanka to evaluate the effect of different establishment methods (farmers' practice, random broadcast, row seeding, seedling broadcast, and transplanted rice) on weedy rice infestation and rice yield. The farmers' practice had a higher number of weedy rice panicles (60-80m-2) than the random broadcast (39-48paniclesm-2), seedling broadcast (3-15paniclesm-2), and transplanted rice (1.3-3.0paniclesm-2) methods. The use of clean rice seeds in the random broadcast method reduced weedy rice seed production by 29-41% compared with the farmers' practice (0.6-2.0tha-1). Compared with the farmers' practice, the seedling broadcast method reduced weedy rice seed production by 71-87% and transplanted rice by 95-98%; and increased rice yield by 27-49% (7.5-9.1tha-1). At all three sites, the farmers' practice resulted in the lowest grain yield (5.1-6.7tha-1). Compared with the farmers' practice, the random broadcast and row seeding methods increased rice yield by up to 21% and 31%, respectively. The findings suggest that the use of clean rice seeds, the use of a row-seeded crop, and the adoption of different rice planting methods may help to suppress the spread of weedy rice. © 2013 Elsevier Ltd.


Chauhan B.S.,International Rice Research Institute | Abeysekara A.S.K.,Rice Research and Development Institute | Kulatunga S.D.,Rice Research and Development Institute | Madusanka I.U.,Rice Research and Development Institute
Journal of Crop Improvement | Year: 2013

Dry-seeded rice (Oryza sativa L.) is an emerging establishment system in irrigated areas in many Asian countries, including Sri Lanka. A field experiment was conducted in the major (Maha) 2011/12 and minor (Yala) 2012 seasons at the research farm of the Rice Research and Development Institute, Sri Lanka, to evaluate the efficacy of several herbicides in an irrigated dry-seeded rice system. Herbicide treatments included propanil, followed by MCPA (2-methyl-4-chlorophenoxyacetic acid), pendimethalin, oxadiazon plus propanil, oxyfluorfen, and pendimethalin, followed by fenoxaprop plus ethoxysulfuron, oxadiazon plus propanil, followed by fenoxaprop plus ethoxysulfuron, and oxyfluorfen followed by fenoxaprop plus ethoxysulfuron. The efficacy of herbicides varied across years. All herbicide-treated plots had lower weed density and weed biomass than the untreated plots. The results suggested that oxyfluorfen applied alone provided the poorest weed control. Generally, there was no effect of the additional spray of fenoxaprop plus ethoxysulfuron on weed biomass at 42 days after planting. However, grain yield was higher in the plots sprayed with the pre-emergence, followed by post-emergence herbicides, compared with the plots sprayed with only pre-emergence herbicide(s). The results suggest that different herbicide options are available in Sri Lanka to effectively control weeds in dry-seeded rice systems. © 2013 Copyright Taylor and Francis Group, LLC.


Gimhani D.R.,Wayamba University of Sri Lanka | Gregorio G.B.,International Rice Research Institute | Gregorio G.B.,East West Seed Company EWS | Kottearachchi N.S.,Wayamba University of Sri Lanka | Samarasinghe W.L.G.,Rice Research and Development Institute
Molecular Genetics and Genomics | Year: 2016

Breeding for salt tolerance is the most promising approach to enhance the productivity of saline prone areas. However, polygenic inheritance of salt tolerance in rice acts as a bottleneck in conventional breeding for salt tolerance. Hence, we set our goals to construct a single nucleotide polymorphism (SNP)-based molecular map employing high-throughput SNP marker technology and to investigate salinity tolerant QTLs with closest flanking markers using an elite rice background. Seedling stage salinity responses were assessed in a population of 281 recombinant inbred lines (RILs) derived from the cross between At354 (salt tolerant) and Bg352 (salt susceptible), by 11 morpho-physiological indices under a hydroponic system. Selected extreme 94 RILs were genotyped using Illumina Infinium rice 6K SNP array and densely saturated molecular map spanning 1460.81 cM of the rice genome with an average interval of 1.29 cM between marker loci was constructed using 1135 polymorphic SNP markers. The results revealed 83 significant QTLs for 11 salt responsive traits explaining 12.5–46.7 % of phenotypic variation in respective traits. Of them, 72 QTLs responsible for 10 traits were co-localized together forming 14 QTL hotspots at 14 different genomic regions. The all QTL hotspots were flanked less than 1 Mb intervals and therefore the SNP loci associated with these QTL hotspots would be important in candidate gene discovery for salt tolerance. © 2016 Springer-Verlag Berlin Heidelberg


Weerakoon W.M.W.,Rice Research and Development Institute | Mutunayake M.M.P.,Rice Research and Development Institute | Bandara C.,Rice Research and Development Institute | Rao A.N.,International Rice Research Institute | And 2 more authors.
Field Crops Research | Year: 2011

About 95% of the rice grown in Sri Lanka is direct-seeded (wet- and dry-seeding). The average rough rice yield in irrigated predominantly direct-seeded dry zone (DZ) is about 5.0tha-1and in the wet zone (WZ) it is about 3.3tha-1. However the average realizable yield in DZ and WZ are 8tha-1 and 5tha-1 respectively. A survey was conducted to understand the cultural practices, farmers' perceptions and the reasons for the yield gap in direct-seeded rice culture in Sri Lanka. Farmers' seed rate ranged from 87 to 220kgha-1 for intermediate bold-type varieties and from 71 to 176kgha-1 for varieties with short round grains. About 90% of the farmers in the DZ and the intermediate zone (IZ) consider both yield potential and duration as criteria in selecting a variety. Among the farmers surveyed, only 21% of the farmers in the DZ, 13% of the farmers in the IZ, and 29% of the farmers in the WZ adhered to the recommended method of basal fertilizer application. Farmers did not adhere to the correct timing of fertilizer application. More than 50% of the cost for rice farming goes to labor, followed by cost of inputs in all climatic zones. Farmers reported that the most important production constraint for direct-seeded rice in the DZ and IZ is the non availability of reliable labor followed by soil problems and weeds. While in the WZ, it is the soil problems specially iron toxicity followed by lower soil fertility. The survey revealed that smaller land holding size, non adherence to the optimum time of farm activity initiation, less efficient use of rain water, higher seed rate and higher cost of production are a few reasons for the existing yield gap. Location-specific technologies for different agro-ecological zones of Sri Lanka should be developed to reduce the cost of production and to increase resource-use efficiency and should be transferred to the farmers to achieve sustainable optimum direct-seeded rice yields. © 2010 Elsevier B.V.


PubMed | Wayamba University of Sri Lanka, International Rice Research Institute and Rice Research and Development Institute
Type: Journal Article | Journal: Molecular genetics and genomics : MGG | Year: 2016

Breeding for salt tolerance is the most promising approach to enhance the productivity of saline prone areas. However, polygenic inheritance of salt tolerance in rice acts as a bottleneck in conventional breeding for salt tolerance. Hence, we set our goals to construct a single nucleotide polymorphism (SNP)-based molecular map employing high-throughput SNP marker technology and to investigate salinity tolerant QTLs with closest flanking markers using an elite rice background. Seedling stage salinity responses were assessed in a population of 281 recombinant inbred lines (RILs) derived from the cross between At354 (salt tolerant) and Bg352 (salt susceptible), by 11 morpho-physiological indices under a hydroponic system. Selected extreme 94 RILs were genotyped using Illumina Infinium rice 6K SNP array and densely saturated molecular map spanning 1460.81cM of the rice genome with an average interval of 1.29cM between marker loci was constructed using 1135 polymorphic SNP markers. The results revealed 83 significant QTLs for 11 salt responsive traits explaining 12.5-46.7% of phenotypic variation in respective traits. Of them, 72 QTLs responsible for 10 traits were co-localized together forming 14 QTL hotspots at 14 different genomic regions. The all QTL hotspots were flanked less than 1Mb intervals and therefore the SNP loci associated with these QTL hotspots would be important in candidate gene discovery for salt tolerance.


Gunaratne A.,Sabaragamuwa University of Sri Lanka | Kao W.,University of Hong Kong | Ratnayaka J.,Rice Research and Development Institute | Collado L.,University of Hong Kong | Corke H.,University of Hong Kong
Journal of the Science of Food and Agriculture | Year: 2013

Background: Hydrothermal treatment used in parboiling could induce formation of novel starch properties having potential food applications. In the current work, functional, digestible and retrogradation properties of flour from non-parboiled and steamed parboiled six rice varieties with high amylose content of around 30% but differing in length and width ratio were investigated and compared. Results: The parboiling process reduced swelling volume and amylose leaching in all tested varieties. Among the varieties studied, the resistant starch content ranged from 1.6% in AT 306 to 0.46% in BG 357. Parboiling reduced the resistant starch content in AT 306 by about 50%, but it did not significantly affect the resistant starch content of the other varieties. The amylose-lipid complex remained unchanged after parboiling. Amylopectin retrogradation was not observed in parboiled rice. Amylose retrogradation was not seen except for AT 306. Pasting behaviour of parboiled rice flours showed high pasting stability and low setback. Flours were more susceptible to enzymatic hydrolysis after parboiling. Partial gelatinisation during parboiling was sufficient to produce grains with excellent milling quality showing a head rice recovery that ranged from 98% to 100% among the varieties studied. Conclusion: Degree of gelatinisation is the most important factor that determines the high head rice recovery. High pasting stability and low setback of flour of parboiled rice indicate some potential food applications. © 2013 Society of Chemical Industry.


Gunaratne A.,Sabaragamuwa University of Sri Lanka | Ratnayaka U.K.,Rice Research and Development Institute | Sirisena N.,Rice Research and Development Institute | Ratnayaka J.,Rice Research and Development Institute | And 3 more authors.
Starch/Staerke | Year: 2011

Functional properties of flour from rice variety BG 250 (short-season) and BG 359 (long-season) exposed to soil water stress from flowering to grain maturity were investigated. Protein content was reduced in both varieties but lipid was reduced only in BG 359 in response to soil moisture stress. AAM content decreased in BG 250 but unaffected in BG 359. Water stress increased swelling power, onset of pasting, peak viscosity, granular breakdown, gel hardness, and cohesiveness in both varieties. Gelatinization temperatures in both varieties were unaffected by water stress, while gelatinization enthalpy was increased in BG 359 but unchanged in BG 250. A double endotherm (type I and type II) appeared in AM-lipid complex in all the flour samples. Type I AM-lipid complex was reduced in BG 359 in response to water stress. Only a single endotherm appeared in the re-formed AM-lipid complex in gelatinized starch. The magnitude of the ΔH of re-formed AM-lipid complex was reduced in BG 359 in response to soil moisture stress, but unaffected in BG 250. Water stress decreased AP retrogradation in BG 359 while it was unaffected in BG 250. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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