Evidence for strong population structure caused by germplasm regeneration in ex situ genebank collections of cauliflower

We used genotyping-by-sequencing (GBS) to characterize the genetic diversity of 191 cauliflower accessions from the USDA and IPK genebanks. They originated from 26 different countries and represent about 50% of all accessions in both genebanks. The analysis of genetic diversity revealed that accessions did not cluster by country of origin but formed two major groups that represented the two genebanks. This finding was robust with respect to the clustering method that included principal component analysis, model-based clustering with STRUCTURE and neighbor-joining trees.