Genomic assessment of white clover and perennial ryegrass genetic resources

Forage resources conserved in genebanks, such as the Margot Forde Forage Germplasm Centre (MFFGC; Palmerston North), are reservoirs of genetic variation that may be utilised to develop cultivars adapted to abiotic stresses and environmental constraints. Genomic tools, including genotyping-by-sequencing (GBS), can be used to extract manageable, genetically-representative subsets from large collections, for phenotypic characterisation. We used GBS to generate SNP (single nucleotide polymorphism) profiles for 203 white clover (WC) and 357 perennial ryegrass (PRG) MFFGC-sourced accessions and estimate relationships amongst accessions within each species. Visualisation of WC relationships aligned accessions along an east-west transect from Kazakhstan to Spain, identifying major diversity in the Caucasus/Central Asia and Iberian Peninsula. A key feature was the reduced diversity present in New Zealand (NZL), Australia, Canada and USA accessions. Similarly for PRG, most NZL accessions coalesced as one group, distinct from clusters associated with the Iberian Peninsula, Italy and Eastern Mediterranean/Caucasian regions. These results emphasise the relatively narrow genetic diversity in NZL WC and PRG germplasm and the broad extent of largely unexploited global diversity. Capturing global genetic variation for each species in manageable core collections would support pre-breeding programmes to mobilise novel genetic variation into NZL-adapted genetic backgrounds, from which cultivars with non-traditional traits, such as enhanced climate resilience and environmental performance may be developed.