Genetic structure of the INRA Capsicum spp. collection using SSR loci: refining the wild origin of cultivated C. annuum and impact of human selection on the structuration of genetic diversity in cultivar types

Germplasm collections of cultivated plants constitute the source for further genetic progress and gained interest with approaches for tracking allelic variants associated to phenotypic variations within core collections. ln order to explore the structure of genetic variation in pepper (Capsicum spp.) and to select core-collections maximizing the genetic and the phenotypic diversity, a pepper collection including 1352 non redundant accessions from Il Capsicum species from 89 different countries was genotyped using 28 microsatellite (SSR) markers spanning the whole genome. Model-based analysis structured the collection into 6 clusters, with 3 clusters separating the main species complexes, including cultivated species and wild relatives, according to botanic classification (C. frutescens/C. chinense, C. baccatum, C. pubescens), and 3 additional clusters for C. annuum. The relationships between the cultivated C. annuum species and the wild relative (C. annnuum var glabriusculum) was refined. The 3 C. annuum clusters were significantly distinct for plant and fruit descriptors corresponding to cultivar types, showing that the genetic structuration of this cultivated species was strongly impacted by the long term hurnan selection of landraces in prirnary as weil as secondary diversification centres. We settled nested core-collections of 8, 16,32, 64 and 128 C annuum accessions capturing from 37% to 90% of the genetic diversity for further sequencing efforts and establishment of high through put genotyping assays. By compiling phenotypic and genotypic data, a larger core-collection of332 accessions was established, capturing 97% of the C. annuum genetic and phenotypic diversity for further genetic association studie