Inheritance of Phenological, Vegetative, and Fruit Chemistry Traits in Black Raspberry

In recent years, there has been renewed interest in black raspberry (Rubus occidentalis L.) breeding. This has been spurred by an increase in black raspberry consumption resulting from 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 northwestern United States, where the commercial black raspberry industry is centered, and fields must be replanted after three to five seasons. An incomplete partial diallel, consisting of 10 parents and 26 sibling families, was constructed for the study of variation and inheritance of phenological, vegetative, and fruit chemistry traits in black raspberry. Sibling families were established at the Oregon State University Lewis Brown Farm in Corvallis and were arranged as a randomized complete block design with four blocks of one to eight plants. Phenological development and vegetative measurements were recorded for each plant in 2005 and 2006. In addition, 25-berry samples of ripe fruit were collected from each plant. To study variation in fruit chemistry properties, including pH, titratable acidity, percent soluble solids, anthocyanin profiles, and total anthocyanins, additional samples of 25 ripe berries were collected from each plant and pooled by family within blocks. Although there were many striking similarities, strong trends in phenotype based on pedigree were observed for most traits indicating a strong genetic component. General combining ability (GCA) effects were significant and larger than specific combining ability effects for all traits, except for fruit size (mass). With the exception of fruit size, narrow-sense heritability estimates were generally moderate to high (0.30 to 0.91), indicating the potential for breeding progress within the population of plants studied. Despite these results, statistically significant and large GCA values were limited to just a few of the parents, indicating a lack of heritable genetic variation in much of the germplasm base and a need for greater diversity.