Use of quantitative trait loci to develop stress tolerance in plants

Abstract Quantitative trait loci (QTLs) refer to a specific region on chromosomes, which harbors gene(s) controlling the traits. QTL mapping tries to identify stretches of DNA closely linked to genes underlying a specific trait by performing statistical analysis of molecular markers and traits in populations of controlled crosses. QTL mapping provides a starting point for dissecting complex traits into its component alleles. It helps to quantify the relative effects of alleles on the traits and locates genomic regions responsible for marker–trait association. Finally, it provides a foundation of marker-assisted selection (MAS) that expedites the breeding process given the proper estimation of position and the effects of QTLs. QTLs that are detected in multiple environments are called stable QTL and are reliable QTL for MAS. Mapping loci in genome requires a population that segregates for the target traits. QTL analysis is performed by estimating the correlation between phenotype data with genotype (markers) data of segregating populations. The primary types of segregating population for QTL mapping include F2, recombinant inbred lines, BC1, double haploid lines, near-isogenic lines, and full-sib F1 (pseudo-testcross).