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