Upland rice, produced by smallholder farmers, is the lowest-yielding rice production system. Drought stress is the most severe abiotic constraint in upland rice. Improving productivity of rice in the upland ecosystem is essential to meet rice food security needs of impoverished upland communities. Breeding drought-resistant upland rice is therefore an increasingly important goal. Numerous secondary characters have been suggested to help plant breeders in their selections. Most of these traits are not used in selection, as they are not practical for selection purposes, exhibit low heritability, or are not highly correlated with grain yield. The use of managed drought stress, where drought stress can be imposed at specific periods, has been shown to increase the heritability of yield under stress to values similar to those obtained for yield in well-watered conditions. It has now been demonstrated that drought-tolerant upland rice can be bred by directly selecting for yield in stress environments. The use of molecular markers to perform selection may eventually provide plant breeders with more efficient selection methods. To date, many quantitative trait loci (QTL) for drought resistance have been identified in rice, but few are suitable for use in marker-assisted selection. However, large-effect drought resistance QTL have now been identified and may enable effective use of marker-assisted selection for drought resistance.
Journal of the Science of Food and Agriculture (2008) 88 (6) 927-939 [doi: 10.1002/jsfa.3153]