SummaryThis study discusses improvement of popular rice varieties under drought through the identification and marker-assisted introgression of drought yield QTLs without any adverse effect on yield under normal conditions.

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BackgroundDrought 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.ResultsARB 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.ConclusionFor 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.

Background Climate extremes such as drought and flood have become major constraints to the sustainable rice crop productivity in rainfed environments. Availability of suitable climate-resilient varieties could help farmers to reduce the grain yield losses resulting from the climatic extremities. The present study was undertaken with an aim to develop high-yielding drought and submergence tolerant rice varieties using marker assisted introgression of qDTY 1.1 , qDTY 2.1 , qDTY 3.1 and Sub1. Performance of near isogenic lines (NILs) developed in the background of Swarna was evaluated across 60 multi-locations trials (MLTs). The selected promising lines from MLTs were nominated and evaluated in national trials across 18 locations in India and 6 locations in Nepal. Results Grain yield advantage of the NILs with qDTY 1.1 + qDTY 2.1 + qDTY 3.1 + Sub1 and qDTY 2.1 + qDTY 3.1 + Sub1 ranged from 76 to 2479 kg ha − 1 and 396 to 2376 kg ha − 1 under non-stress (NS) respectively and 292 to 1118 kg ha − 1 and 284 to 2086 kg ha − 1 under reproductive drought stress (RS), respectively. The NIL, IR96322–34-223-B-1-1-1-1 having qDTY 1.1 + qDTY 2.1 + qDTY 3.1 + Sub1 has been released as variety CR dhan 801 in India. IR 96321–1447-651-B-1-1-2 having qDTY 1.1 + qDTY 3.1 + Sub 1 and IR 94391–131–358-19-B-1-1-1 having qDTY 3.1 + Sub1 have been released as varieties Bahuguni dhan-1′ and ‘Bahuguni dhan-2’ respectively in Nepal. Background recovery of 94%, 93% and 98% was observed for IR 96322–34-223-B-1-1-1-1, IR 96321–1447-651-B-1-1-2 and IR 94391–131–358-19-B-1-1-1 respectively on 6 K SNP Infinium chip. Conclusion The drought and submergence tolerant rice varieties with pyramided multiple QTLs can ensure 0.2 to 1.7 t ha − 1 under reproductive stage drought stress and 0.1 to 1.0 t ha − 1 under submergence conditions with no yield penalty under non-stress to farmers irrespective of occurrence of drought and/or flood in the same or different seasons. Electronic supplementary material The online version of thi...

Highlights Genetic gain for rice grain yield for International Rice Research Institute drought breeding program was estimated. Positive trend of 0.68 %, 0.87 %, 1.9 % under irrigated control, moderate and severe drought achieved. Superiority of new rice varieties over currently grown demonstrated on farmers’ fields. International Rice Research Institute developed rice varieties can protect farmers from crop losses under drought conditions.