Locating genomic regions associated with components of drought resistance in rice: comparative mapping within and across species

Direct and indirect economic loss in the agricultural sector due to drought is huge. With the advent of molecular-marker technology, research on drought resistance in crop plants has shifted from physiological descriptions of the phenomenon to genetic dissection of the mechanisms involved. Here, we report a comprehensive study of mapping the drought resistance components (osmotic adjustment and root traits) in a doubled-haploid rice (Oryza sativa L.) population of 154 lines. A genetic linkage map consisting of 315 DNA markers was constructed. A total of 41 quantitative trait loci (QTLs) were identified for osmotic adjustment and root traits, and individually explained 8-38% of the phenotypic variance. A region on chromosome 4 harbored major QTLs for several root traits. Consistent QTLs for drought responses across genetic backgrounds were detected and should be useful for marker-assisted selection towards the incorporation of a trait of interest into an elite line. Comparative mapping identified three conserved genomic regions associated with various physiological responses to drought in several grass species. These results suggest that these regions conferring drought adaptation have been conserved across grass species during genome evolution and might be directly applied across species for the improvement of drought resistance in cereal crops.