Abstract
Drought is one of the most predominant abiotic stresses in this century, leading to a drastic reduction in the yield of rainfed rice ecosystems. Breeding of drought-resilient rice varieties is very much in demand for sustainable rice production in drought-prone rainfed ecology. An experiment was designed under irrigated non-stress and drought-stress situations involving an exotic drought-tolerant landrace (Chao Khaw) and a high-yielding aromatic rice cultivar (Kasturi), and an F2:4 derived population of 156 breeding lines was developed at IRRI South Asia Hub, Hyderabad. The objective of the study was to assess the genetic variability, drought tolerance behavior, and identify promising breeding lines for different rice ecologies and drought breeding programs. Restricted maximum likelihood (REML) analysis using the mixed model approach revealed a considerable genetic variation in the population for yield and yield contributing traits in non-stress and drought-stress conditions. We observed very high heritability for all the selected traits under stress 2015 WS (73.8% to 85.3%) and 2016 WS (72.4% to 93.5%) and non-stress 2015 WS (68.2% To 92.9%) and 2016 WS (61.4% to 92.6%) environments, indicating possible selection for grain yield under drought stress and non-stress with the same precision level. None of the secondary traits except harvest index and biomass included in our study showed a positive association with grain yield, indicating indirect selection’s ineffectiveness in improving yield under drought. A total of 48 promising breeding lines were found to have a better yield than donor Chao Khaw (up to 38% advantage) and popular drought-tolerant cultivars Shabhagidhan (up to 48% advantage) in stress conditions and recommended for rainfed upland ecology, 34 breeding lines under the well-watered condition suited for rainfed lowland ecology. Overall, the study found 21 common breeding lines that showed their superiority in non-stress and under drought stress situations, fitting best in rainfed lowland ecology with occasional drought occurrence. The large genetic variation found in this population can be exploited further to develop a few forward breeding high-yielding lines with better drought tolerance ability and used as drought donors in drought breeding programs.
Highlights
Climate change is not a myth but a fact, which becomes a great threat to society due to its potential to intensify extreme events such as drought around the globe
The yield reduction in droughttolerant parent Chao Khaw under drought-stress environments (DSE), DSE-2015, and DSE-2016 was 61.72% and 54.12%, respectively, whereas the reduction was much higher in droughtsensitive parent Kasturi in DSE-2015 (80.03%) and DSE-2016 (82.78%)
We found that all the 21 breeding lines are semidwarf plant types (92–109 cm in non-stress and 75–86 cm in stress days)
Summary
Climate change is not a myth but a fact, which becomes a great threat to society due to its potential to intensify extreme events such as drought around the globe. Increased global temperatures and frequent changes in monsoon primarily cause the occasional droughts and floods, more common in many rice-growing areas in South and Southeast Asia. Rice is the most widely consumed staple food as a cereal grain, is one of the most water-intensive crops, and grows about in the 25.12 million hectares area in irrigated conditions and 42.75 million hectares in lowland conditions in India. Rice consumes about 80% of irrigated freshwater resources worldwide (Wu et al, 2017). 15–20 million hectares of irrigated rice will face water scarcity by 2025 (Wu et al, 2017). It is a great challenge for the farmers to produce rice with limited water to meet the growing population’s food demand
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