Progress Towards Identification and Validation of Candidate Genes for Abiotic Stress Tolerance in Wheat

Abstract

Identification of candidate gene(s) and its validation in a breeder’s germplasm is a prerequisite for any successful marker-assisted selection (MAS) programme for improving abiotic stress tolerance. Once a candidate gene(s) is identified and its effects validated under a stress environment, it becomes a powerful marker resource for developing ‘functional markers’ to assist genomics-assisted breeding in crops. There are several ways to identify a candidate gene(s) underpinning a specific abiotic stress tolerance mechanism. The most common methods used are various ‘omics’ approaches targeting transcriptome (transcriptomics), metabolome (metabolomics) or proteome (proteomics), co-location of genes with quantitative trait loci (QTLs) for abiotic stress tolerance traits (called positional candidates), fine mapping of QTLs/QTL cloning, transgenics, RNA interference, mutant screenings and genome wide/candidate gene-based association mapping among others. The advent of next generation sequencing (NGS) technologies has completely revolutionized the identification and characterization of candidate genes underlying various abiotic stress tolerance traits. This review focuses on the approaches taken to identify and validate candidate genes for various abiotic stress tolerances in wheat and the progress made so far in their validation and implementation in wheat breeding programs globally.