Genetic gain for rice yield in rainfed environments in India

Area of Science:

• Plant breeding
• Agronomy
• Genetics

Background:

• Genotype × environment interactions under drought complicate selection for drought tolerance.
• Heritability is reduced by drought stress, impacting the development of drought-tolerant varieties.
• Measuring genetic gain is crucial for assessing the efficiency of plant breeding programs.

Purpose of the Study:

• To determine the annual rate of genetic gain for rice grain yield in a drought-prone rainfed system.
• To evaluate the effectiveness of breeding efforts for drought tolerance over a decade.
• To assess the impact of drought stress on genetic gain in rice.

Main Methods:

• Multi-environment trials were conducted from 2005 to 2014 under the Drought Breeding Network of Indian sites.
• Trials included irrigated control and managed drought stress conditions (moderate and severe).
• Annual genetic gain for grain yield was calculated under different environmental conditions.

Main Results:

• A positive trend in grain yield was observed, with annual genetic yield increases of 0.68% (irrigated), 0.87% (moderate drought), and 1.9% (severe drought).
• Direct selection for grain yield under both irrigated and drought stress conditions proved effective.
• The International Rice Research Institute's (IRRI) drought breeding program showed significant positive genetic gain for grain yield.

Conclusions:

• IRRI's breeding program has successfully achieved genetic gain in rice grain yield under both drought and favorable conditions.
• Released drought-tolerant varieties have outperformed existing varieties in farmers' fields in rainfed environments.
• Direct selection strategies are effective for improving rice yield in rainfed systems prone to drought.