Identification of founding accessions and patterns of relatedness and inbreeding derived from historical pedigree data in a white clover germplasm collection in New Zealand.

Pedigrees provide suitable input for tracking breeding crosses and monitor plants and animal populations. Pedigree analysis is an essential tool to visualise and describe population structure and genetic diversity. Pasture plant breeding relies on a range of strategies from closed system recurrent selection to diversity focused programmes using ecotypes and wild accessions as direct parents of cultivars. There is currently no published pedigree analysis of pasture plants, despite a century of breeding efforts. A pedigree map was constructed for white clover (Trifolium repens L.) germplasm stored in the Margot Forde Germplasm Centre (MFGC) located in Palmerston North, New Zealand conserved since 1940s. Inbreeding and kinship coefficients and the effective number of founders through time were estimated to assess genetic relatedness in the reference population. A total of 15,265 accessions were included in the map. The maximum number of traced generations was 15 and the mean completeness of parentage for the reference population was 72%. The mean number of offspring was 5.14. The origin of founding and introduced accessions was assessed. The effective number of founders was 175.68 or 17.5% of the total number of reference founders. Accessions with large contributions and founding and influencing ancestors were identified. Relatedness was determined using the k coefficient, with k=1 as complete relatedness. The overall mean relatedness was k=0.002. Overall mean inbreeding level was 0.39%. Relatedness and inbreeding coefficients revealed distinct germplasm pools formed across time that are of interest to pre-breeding efforts.