ARS | Publication request: Genetic diversity in wild and cultivated black raspberry evaluated by simple sequence repeat markers

Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2011
Publication Date: February 26, 2012
Repository URL: http://www.springerlink.com/content/71611805663p3318/fulltext.pdf
Citation: Dossett, M., Bassil, N.V., Lewers, K.S., Finn, C.E. 2012. Genetic diversity in wild and cultivated black raspberry evaluated by simple sequence repeat markers. Genetic Resources and Crop Evolution. DOI:10.1007/s10722-012-9809-8.

Interpretive Summary: A survey was conducted of genetic markers in 137 wild and 21 cultivated black raspberries. The objective was to compare genetic diversity, to figure out family relationships, and to determine the best parents to cross. Overall, genetic diversity was much lower in the cultivated types than that found in wild black raspberries. Black raspberry cultivars were closely related. Discrepancies in the fingerprints of some black raspberry cultivars and their parents were found. Six black raspberry cultivars had identical genetic fingerprints and could not be separated. They may have been mislabelled in the past decades or the genetic markers available may not be good enough to differentiate between them. In contrast to cultivated types, wild black raspberries were very diverse and individuals were highly inbred. Differentiation between wild types is strong. Wild populations may be inbred from either strong population founder effects and/or isolation. For the most part, differentiation between wild black raspberry populations does not appear to show strong geographical trends. Some evidence suggests that diversity in wild black raspberry has not been fully sampled. Several wild populations clustered with cultivated black raspberry, however, most of these had larger-than average fruit or other traits indicating that they may be escaped seedlings from cultivated plants. This study has shown that wild black raspberries will broaden the genetic pool for breeding populations and will improve the long-term breeding progress in this crop.

Technical Abstract: Breeding progress in black raspberry (Rubus occidentalis L.) has been limited by a lack of genetic diversity in elite germplasm. Black raspberry cultivars have been noted for showing very few phenotypic differences and seedlings from crosses between cultivars for a lack of segregation for important traits. Despite these challenges, little molecular work has been done to explore genetic diversity and relationships in wild and cultivated black raspberry germplasm. Microsatellite, or simple sequence repeat (SSR), markers are highly polymorphic codominant markers useful for studying genetic diversity, population genetics, genetic fingerprinting and other applications. Using 21 polymorphic SSR markers, we examined genetic diversity in 148 wild and cultivated black raspberry accessions. Black raspberry cultivars clustered tightly and showed higher than expected heterozygosity while heterozygosity of wild accessions was low. Relationships between wild black raspberry accessions were poorly resolved and regional clusters were mostly absent from our analysis. Our results indicate that wild black raspberry germplasm is a relatively untapped resource available for future breeding.