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 droug ht 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 m arkers was constructed. A total of 41 quantitative trait loci (QTLs) were i dentified for osmotic adjustment and root traits, and individually explaine d 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 l ine. Comparative mapping identified three conserved genomic regions associa ted with various physiological responses to drought in several grass specie s. These results suggest that these regions conferring drought adaptation h ave been conserved across grass species during genome evolution and might b e directly applied across species for the improvement of drought resistance in cereal crops.