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Kumar A.,International Rice Research Institute | Verulkar S.B.,Indira Gandhi Krishi Vishwavidyalaya IGKV | Mandal N.P.,Central Rainfed Upland Rice Research Station CRURRS | Variar M.,Central Rainfed Upland Rice Research Station CRURRS | And 12 more authors.
Field Crops Research | Year: 2012

High and stable yield of rainfed lowland rice is important for sustainable rice production and food security. Many varieties grown on large holdings in rainfed areas provide good yield under normal water availability but suffer high losses in the event of drought. From a set of 129 genotypes tested in shallow rainfed drought-prone environments at three locations in eastern India from 2005 to 2007, a subset of 39 genotypes that were tested for two or more years under favorable irrigated, moderate reproductive-stage drought stress, and severe reproductive-stage drought stress situations in 16 environments was selected for a GGE biplot analysis to identify genotypes that provide stable yield across environments. IR74371-70-1-1 and IR74371-46-1-1 were identified as stable genotypes showing high yield under varied environments across different sites. IR36, IR64, and MTU1010, the three popular varieties grown on large holdings in rainfed areas but bred for irrigated ecosystem, as well as improved genotypes CB2-458, DGI237, R1027-2282-2-1, RR272-21, IR67469-R-1-1, and IR66873-R-11-1, and varieties PMK1 and PMK2 released for rainfed ecosystems performed well only in irrigated non-stress environments and were not found promising in drought environments. Improved genotypes ARB6, ARB2, ARB5, ARB7, ARB8, RF5329, CB0-15-24, IR72667-16-1-B-B-3, IR74371-78-1-1, and IR55419-04, and drought-tolerant released varieties Tripuradhan, Annada, and Poornima performed well only in drought-stress environments. The identification of improved genotypes with ability to provide stable high yield across variable environments and their release for cultivation by farmers will enable farmers to reap high yield and stable income. © 2012 Elsevier B.V..

Swamy B. P. M.,International Rice Research Institute | Ahmed H.U.,International Rice Research Institute | Henry A.,International Rice Research Institute | Mauleon R.,International Rice Research Institute | And 21 more authors.
PLoS ONE | Year: 2013

Background:Rice (Oryza sativa L.) is a highly drought sensitive crop, and most semi dwarf rice varieties suffer severe yield losses from reproductive stage drought stress. The genetic complexity of drought tolerance has deterred the identification of agronomically relevant quantitative trait loci (QTL) that can be deployed to improve rice yield under drought in rice. Convergent evidence from physiological characterization, genetic mapping, and multi-location field evaluation was used to address this challenge.Methodology/Principal Findings:Two pairs of backcross inbred lines (BILs) from a cross between drought-tolerant donor Aday Sel and high-yielding but drought-susceptible rice variety IR64 were produced. From six BC4F3 mapping populations produced by crossing the +QTL BILs with the -QTL BILs and IR64, four major-effect QTL - one each on chromosomes 2, 4, 9, and 10 - were identified. Meta-analysis of transcriptome data from the +QTL/-QTL BILs identified differentially expressed genes (DEGs) significantly associated with QTL on chromosomes 2, 4, 9, and 10. Physiological characterization of BILs showed increased water uptake ability under drought. The enrichment of DEGs associated with root traits points to differential regulation of root development and function as contributing to drought tolerance in these BILs. BC4F3-derived lines with the QTL conferred yield advantages of 528 to 1875 kg ha-1 over IR64 under reproductive-stage drought stress in the targeted ecosystems of South Asia.Conclusions/Significance:Given the importance of rice in daily food consumption and the popularity of IR64, the BC4F3 lines with multiple QTL could provide higher livelihood security to farmers in drought-prone environments. Candidate genes were shortlisted for further characterization to confirm their role in drought tolerance. Differential yield advantages of different combinations of the four QTL reported here indicate that future research should include optimizing QTL combinations in different genetic backgrounds to maximize yield advantage under drought. © 2013 Swamy B.

Raman A.,International Rice Research Institute | Verulkar S.B.,Indira Gandhi Krishi Vishwavidyalaya IGKV | Mandal N.P.,Central Rainfed Upland Rice Research Station CRURRS | Variar M.,Central Rainfed Upland Rice Research Station CRURRS | And 14 more authors.
Rice | Year: 2012

Background: Drought is the most severe abiotic stress reducing rice yield in rainfed drought prone ecosystems. Variation in intensity and severity of drought from season to season and place to place requires cultivation of rice varieties with different level of drought tolerance in different areas. Multi environment evaluation of breeding lines helps breeder to identify appropriate genotypes for areas prone to similar level of drought stress. From a set of 129 advanced rice (Oryza sativa L.) breeding lines evaluated under rainfed drought-prone situations at three locations in eastern India from 2005 to 2007, a subset of 39 genotypes that were tested for two or more years was selected to develop a drought yield index (DYI) and mean yield index (MYI) based on yield under irrigated, moderate and severe reproductive-stage drought stress to help breeders select appropriate genotypes for different environments. Results: ARB 8 and IR55419-04 recorded the highest drought yield index (DYI) and are identified as the best drought-tolerant lines. The proposed DYI provides a more effective assessment as it is calculated after accounting for a significant genotype x stress-level interaction across environments. For rainfed areas with variable frequency of drought occurrence, Mean yield index (MYI) along with deviation in performance of genotypes from currently cultivated popular varieties in all situations helps to select genotypes with a superior performance across irrigated, moderate and severe reproductive-stage drought situations. IR74371-70-1-1 and DGI 75 are the two genotypes identified to have shown a superior performance over IR64 and MTU1010 under all situations. Conclusion: For highly drought-prone areas, a combination of DYI with deviation in performance of genotypes under irrigated situations can enable breeders to select genotypes with no reduction in yield under favorable environments compared with currently cultivated varieties. For rainfed areas with variable frequency of drought stress, use of MYI together with deviation in performance of genotypes under different situations as compared to presently cultivated varieties will help breeders to select genotypes with superior performance under all situations. © 2012 Raman et al.

Verulkar S.B.,Indira Gandhi Krishi Vishwavidyalaya IGKV | Mandal N.P.,Central Rainfed Upland Rice Research Station CRURRS | Dwivedi J.L.,Narendra Dev University of Agriculture and Technology | Singh B.N.,Birsa Agricultural University | And 20 more authors.
Field Crops Research | Year: 2010

Drought is the predominant cause of yield reduction in rainfed rice production systems, but until recently, little systematic effort has been made to breed drought-tolerant cultivars. The complex nature of drought tolerance, genotype×environment interaction, and the difficulty of effective drought tolerance screening complicate the development of drought tolerant varieties. This study reports on progress made by a collaborative network of Indian rice breeding programs, in partnership with International Rice Research Institute (IRRI), to develop lines combining high yield potential with drought tolerance by employing direct selection for grain yield under drought stress, and testing their performance in rainy season managed-drought screenings (RSMDS) of different stress severity levels at several locations during the main season in rainfed rice production areas in India. Advanced-generation breeding lines of less than 100 days, 100-120 days, and greater than 120 days duration generated at eight national institutes and IRRI using diverse drought tolerant donors were evaluated in 2005-2007 under RSMDS. Stress was imposed at the reproductive stage, either by draining paddies shortly after transplanting for lowland trials, or by stopping irrigation before flowering for upland trials. Yield reduction of 34-53% under moderate stress and 65-88% under severe stress was achieved in comparison to irrigated controls. Several varieties that have been widely grown in rainfed environments in India for many years, including IR 36, IR 64, Mahamaya, Sambha Mahsuri, and Swarna, were shown to be highly susceptible. Breeding lines were identified that perform consistently better than these and other widely grown rainfed varieties under both moderate and severe drought stress without any yield penalty under fully irrigated conditions. In the combined analysis over locations and years, these promising breeding lines outyielded the widely grown controls by about 0.5tha-1 under moderate stress and 0.7-1.0tha-1 under severe stress. IRRI breeding lines contributed to the network were developed using a selection protocol involving replicated dry season managed-drought screening (DSMDS) in dry season at Los Banos, Philippines. For a subset of lines extensively tested both at IRRI and in India, correlations between yield under DSMDS in the Philippine and yield in RSMDS in India were moderately high, indicating the efficacy of dry-season MS screening at IRRI in identifying tolerant lines for India. Drought tolerant lines developed by the network members have been released in several Indian states and in the Philippines. Overall, these results indicate that managed stress screening for drought tolerance, with a focus on selection for yield under stress, is effective in generating drought-tolerant cultivars. © 2010 Elsevier B.V.

Mishra V.N.,Indira Gandhi Krishi Vishwavidyalaya IGKV | Maruti Sankar G.R.,Indian Central Research Institute for Dryland Agriculture | Patil S.K.,Indira Gandhi Krishi Vishwavidyalaya IGKV | Srivastava L.K.,Indira Gandhi Krishi Vishwavidyalaya IGKV | Rao C.S.,Indian Central Research Institute for Dryland Agriculture
Communications in Soil Science and Plant Analysis | Year: 2015

Soil-test crop-response experiments on rice were conducted in the Bastar Plateau Agroclimatic Zone of Chhattisgarh during 2009–2011 to assess yield, soil, plant, and fertilizer nitrogen (N), phosphorus (P), and potassium (K) nutrient relationships and calibrate optimum fertilizer doses for attaining yield targets. Soil fertility status was poor to medium for N (194–283 kg ha−1) and P (7.53–19.66 kg ha−1), and medium to good for K (226–320 kg ha−1). Based on nutrient requirements (NR, kg q−1) and contributions from soil (CS, %), fertilizer (CF, %), and farmyard manure (CFYM, %), optimum fertilizer doses were derived. The fertilizer doses were validated for attaining yield targets of 5000 and 6000 kg ha−1 in farmer’s fields. Rice yield within 10% deviation was attained, which indicated that soil-test-based fertilizer dose was superior. This approach could be adopted for regions with similar soil and agroclimatic conditions in other parts of the world to increase rice yields. Copyright © Taylor & Francis Group, LLC.

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