Introducing Beneficial Alleles from Plant Genetic Resources into the Wheat Germplasm

Many crops including wheat have a narrow genetic base after hundreds of years of breeding and selection. This makes it difficult to breed new varieties with increased yields to feed the growing global population, and with stronger tolerance to the wider range of biotic and abiotic stresses that are anticipated with climate change. Thus, there is a need to introduce new genetic diversity into wheat breeding programs. Plant genetic resources stored in genebanks and the wild relatives of crops are potential sources of new genetic diversity. Here, we discuss the importance of these resources for breeding new wheat cultivars, and outline where they are currently stored and used. We also discuss pre-breeding, where genetic regions associated with desirable traits are identified and transferred into materials ready for use in breeding programs. Pre-breeding in wheat, when conducted in close collaboration with breeders, farmers, and end-users, has contributed to many outstanding varieties and novel beneficial diversity. This review addresses various genetic and genomic considerations for the strategic transfer of this useful diversity. Wheat (Triticum sp.) is one of the world's most important crops, and constantly increasing its productivity is crucial to the livelihoods of millions of people. However, more than a century of intensive breeding and selection processes have eroded genetic diversity in the elite genepool, making new genetic gains difficult. Therefore, the need to introduce novel genetic diversity into modern wheat has become increasingly important. This review provides an overview of the plant genetic resources (PGR) available for wheat. We describe the most important taxonomic and phylogenetic relationships of these PGR to guide their use in wheat breeding. In addition, we present the status of the use of some of these resources in wheat breeding programs. We propose several introgression schemes that allow the transfer of qualitative and quantitative alleles from PGR into elite germplasm. With this in mind, we propose the use of a stage-gate approach to align the pre-breeding with main breeding programs to meet the needs of breeders, farmers, and end-users. Overall, this review provides a clear starting point to guide the introgression of useful alleles over the next decade.