Genotyping-by-sequencing highlights original diversity patterns within a European collection of 1191 maize flint lines, as compared to the maize USDA genebank
Résumé
Comparing and identifying interesting sources of genetic diversity that have been maintained by different genebanks and understanding the global organization of this genetic diversity is an important issue for pre-breeding. We aimed at evaluating how genotyping-by-sequencing (GBS) technologies can address these both issues. We used GBS to compare the genetic diversity of 1191 European Flint lines maintained by INRA and other European institutes (see Gouesnard et al., this meeting) with the USDA collection (Romay et al., 2013, Genome Biology). We first examined the similarity of 68 inbred lines with a same variety name between the two collections, and observed that IBS ranged from 0.775 to 0.997 (with a mean of 0.941). It indicated that GBS can be used for comparing collections and identifying redundancy and illegitimate accessions between genebanks. Based on principal coordinate analysis and structure analysis on 4001 lines, we showed the distinctiveness of flint materials compared to the USDA collection. The structuration analysis in 12 groups confirmed the influence of some historical founder lines in the genetic organization of the dent group (B73, A632, Oh43, Mo17, W182E, PH207 and Wf9). Flint lines were structured in 3 groups (a Sweet-Northern Flint group, an Italian-Argentinan group and a European group formed by Pyrenees Galicia and Lacaune groups). The Tropical and Pop corn groups were distinct. We identified several selective sweeps between Dent, Flint and Tropical inbred lines that co-localized with SNPs associated with flowering time variation identified by association mapping. It suggests that these genomic regions played an important role in adaptation to higher lattitude. The joint analysis of collections by GBS offers opportunities for a global diversity analysis of maize inbred lines.