Rainfed rice ecosystems account for more than 80% of the total rice area in sub-Saharan Africa, and large parts of this region frequently experience drought stress. One potential approach to improve the drought resistance and local adaptation of high-yielding rice varieties in rainfed regions of sub-Saharan Africa is to cross them with the African rice species Oryza glaberrima. In this study, 200 introgression lines (ILs) from crosses of O. sativa (IR64) and O. glaberrima (RAM90 and RAM54) were evaluated in three field experiments under different rainfed drought scenarios in Tanzania and the Philippines. The objectives of the study were to select ILs for yield and traits associated with drought resistance, and to analyze the genetic variation in water uptake, root growth, and drought response that were observed among the ILs in a previous greenhouse lysimeter study. Several ILs showed improved yield under drought stress and well-watered conditions compared with the recurrent parent IR64. One cluster of ILs that showed the highest yield across all environments included genotypes with the lowest canopy temperature under drought. In 10 selected ILs, root length density was negatively correlated with canopy temperature and soil moisture, and positively related to shoot biomass, but not significantly correlated with grain yield under drought. Although root growth in the field correlated well with root growth in the previous lysimeter study, only some of the highest-yielding lines under drought in the field were those that showed more water uptake in lysimeters. These results confirm the complex relationship among grain yield, root growth, and additional physiological mechanisms underlying crop growth and productivity in the field. The high-yielding ILs under both drought and well-watered conditions in this study can be used as donors to improve drought resistance in target rainfed rice environments in sub-Saharan Africa.
Kijoji, A.A.; Nchimbi-Msolla, S.; Kanyeka, Z.L.; Serraj, R.; Henry, A. Linking root traits and grain yield for rainfed rice in sub-Saharan Africa: Response of Oryza sativa×Oryza glaberrima introgression lines under drought. Field Crops Research (2014) 165: 25-35. [DOI: 10.1016/j.fcr.2014.03.019]