Evaluation of genetic diversity in wild populations of black raspberry (Rubus occidentalis L.)

Graduation date: 2011In recent years, there has been renewed interest in black raspberry (Rubus\ud occidentalis L.) breeding. This has been spurred, in part, by an increase in black\ud raspberry consumption due to studies that have shown them to be particularly high in\ud anthocyanin content indicating high levels of antioxidants. Present cultivars are ill\ud adapted to the biotic and abiotic stresses of the Pacific Northwest, where the\ud commercial black raspberry industry is centered, and fields must be replanted after 3-5 seasons. Breeding progress in black raspberry has been limited by a lack of genetic\ud diversity. This work is the first documented effort to systematically collect and\ud evaluate wild R. occidentalis germplasm from across the native range of the species.\ud Sources of strong resistance to the virus vector Amphorophora agathonica Hottes\ud were identified from Maine, Michigan, and Ontario. Populations with outstanding\ud vigor and possible resistance to Verticillium wilt were identified, as were two\ud populations with a novel anthocyanin profile. In addition, variation was documented\ud for morphological traits such as thorniness and cane architecture as well as fruit\ud weight and gloss, and ripening times. Molecular analysis of genetic diversity using\ud microsatellite markers in these populations showed that black raspberry cultivars are\ud closely related to each other, but there is tremendous diversity in the wild\ud populations. The data also support phenotypic evidence that several "wild" populations may be descended from feral cultivated plants. Overall, genetic diversity\ud in wild black raspberry germplasm shows tremendous potential for use in breeding\ud improved cultivars