Genome-Wide, High-Density Genotyping Approaches for Plant Germplasm Characterisation (Methods and Applications)

Germplasm collections are a treasure trove of humanity. The accessions constituting those collections (wild crop relatives, landraces, cultivars, etc.) contain genes and allelic variants, which evolved prior to or post domestication, in the course of adaptation and selection, and can be used in breeding to address current and future needs. Precise characterisation of genetic diversity is essential for the efficient conservation of genetic resources and their effective utilisation in crop improvement. Detailed genetic profiles resulting from DNA genotyping constitute a basis for establishing the level of genetic diversity of a collection, analysing population structure, identifying redundancies, performing genome-wide association scans (given the availability of phenotypic information), detecting loci under selection, and many other applications. To obtain an accurate picture of genetic diversity (at the DNA sequence level), robust, high-density, high-throughput, and cost-effective methods are needed. With the advances in the next-generation sequencing, new genotyping approaches emerged (such as genotyping-by-sequencing, whole genome resequencing), which provide excellent genome coverage and low cost per datapoint (with tens of thousands to millions of loci analysed in a single assay). Crop-specific, custom, microarray-based genotyping solutions were also developed. The aim of this review is to provide a comparative description of the genome-wide, high-density genotyping technologies that are most frequently used nowadays, comprising their advantages and drawbacks, as well as factors that determine, which of the methods will best suit the particular germplasm characterisation project. Further, we characterise the current role of these methods in addressing the challenges related to the effective management and use of genetic resources and present recent examples of their application in selected crop plant groups. Finally, we briefly describe constraints to germplasm characterisation and future prospects.