Quantitative Trait Loci and Breeding

AbstractPlant breeding methodologies have changed greatly over the past century as new techniques and tools become available to breeders. The introduction of computer technologies, new statistical methods and molecular markers have greatly enhanced the rates of genetic gain that can be achieved in breeding programs. Many important traits for crop improvement, such as yield, quality and quantitative or durable disease resistances, are regarded as quantitative traits and are controlled by multiple quantitative trait loci (QTL). Recent advances in molecular marker systems have created new opportunities and strategies to select for quantitative traits. Strategies for deploying QTL in breeding programs vary from monitoring specific loci through to the deployment of molecular markers flanking the target QTL to the use of whole‐genome marker scans to identify individual plants that will offer the greatest opportunity for genetic gain.Key Concepts:Yield, many aspects of quality and durable disease resistance are all examples of quantitative traits.Interactions between the genotype of the plants and the growing environment can be critical in determining the expression of quantitative traits.Breeding programs usually select for quantitative traits at multiple stages in the breeding process and using replicated trials across multiple locations.The regions of the genome controlling quantitative traits, QTL, can be mapped by measuring the association between molecular markers and the phenotype across multiple environments in populations segregating for the trait.The stability of QTL across environments and the proportion of the variation accounted for by the QTL are key criteria in determining the value of the QTL to a breeding program.Genomic selection, based on whole‐genome scan with markers, offers an opportunity to select for large numbers of minor QTL without prior knowledge of the location of the QTL.Effective delivery of molecular breeding technologies to breeding programs, particularly in poor countries, is dependent on providing access to marker screening platforms resources, and training.