Knowledge regarding gene bank accessions characters facilitates the identification of the most promising for future use. Sampling of accessions from a cultigen available at a gene bank may be based on diversity and variability analysis relying on characterization or evaluation data, DNA markers, or both. Core subsets may aid selection by guiding users to genetic differences. Evaluation results must be shared promptly and widely worldwide, so germplasm users can request them for further utilization in plant breeding or research on plant genetic resources. This chapter relates therefore to gathering accurate and precise evaluation of diverse accessions in well-designed trials. Such knowledge is essential for identifying the most relevant accessions for further use. This information needs to be shared widely and quickly with users to achieve a maximum impact because any germplasm user should be aware of the potential of gene bank accessions in order to fully exploit such plant genetic resources.This chapter also illustrates the need for an objective assessment of gene bank accessions, deals with sampling of core subsets for evaluation of gene bank accessions, explains the principles of experimental design for trials of gene bank accessions and provides basic knowledge regarding trial data analysis.

This chapter provides an overview of genetic diversity and variation and how to measure this when studying plant genetic resources. It also describes the use of DNA markers for assessing polymorphism, studying diversity and revealing trait associations relevant for searching variation of target characters in plant breeding. The goal of this chapter is therefore to highlight various methods for analyzing the range of genetic diversity and of character variation to facilitate their further use in plant breeding. The information given herein will allow to understand genetic diversity, gene polymorphism and genetic variation; assess how various techniques – based on population and quantitative genetics – are used for assessing genetic diversity and trait variation in plant germplasm; and determine how the data generated can be effectively analyzed.