Drought resistance in an interspecific backcross population of rice (Oryza spp.) derived from the cross WAB56-104 (O. sativa) × CG14 (O. glaberrima)

The ability to identify drought-resistant lines in all seasons would accelerate variety introduction. A total of 202 backcross-inbred lines of rice were subjected to drought during the 2006 and 2007 dry seasons at AfricaRice in Benin. Two irrigation regimes were applied: fully irrigated to maturity and 21 days of drought from 45 days after sowing. Plants were harvested at maturity. Increased canopy temperature under drought as compared to fully irrigated condition was observed. Delays were observed in plant flowering and maturity, with drought susceptibility index reaching 26.8 for flowering. Plant leaves were greener (2.9% increase) under drought than when fully irrigated. Drought negatively affected tiller number, plant height, number of leaves, leaf width and grain yield (16.9%, 13.7%, 6.7%, 14.1% and 26.7% respective reductions). Highly significant (P ≤ 0.01) correlations were observed between traits measured under fully irrigated and drought conditions (r between 0.52 and 0.92), except for leaf greenness (SPAD), leaf width and canopy temperature (r = 0.42 ns, −0.03 ns and −0.30**, respectively). The study identified canopy temperature, SPAD, plant height and leaf number as possible traits that best correlated with grain yield. The performance of these traits under drought was a function of the rice line.