Chad E. Finn
Chad E. Finn
Michael Dossett and Chad E. Finn
The large raspberry aphid (Amphorophora agathonica Hottes) is an important vector of viruses in Rubus L. across North America. Although breeding for aphid resistance has long been recognized as an important tool for protecting red raspberries (Rubus idaeus L.) from viral infection, this is the first report of resistance to A. agathonica in black raspberry (Rubus occidentalis L.). Seedlings from 132 wild populations of black raspberries, representing the species' native range, were screened for resistance to A. agathonica. Strong resistance was found in three of these populations, one from Ontario (ORUS 3778), one from Maine (ORUS 3817), and one from Michigan (ORUS 4109). Resistance to the large raspberry aphid in ORUS 3778 and ORUS 3817 is dominant and appears to be conferred by different genes. We propose that the genes for resistance in ORUS 3778 and ORUS 3817 be designated Ag4 and Ag5, respectively. Resistance to A. agathonica in ORUS 4109 also appears to be controlled by a dominant allele at a single locus, but cannot be differentiated from Ag4 at this time.
Jack Pinkerton and Chad E. Finn
The relative susceptibility of 44 genotypes of wild Fragaria L. and commercial cultivars of strawberry Fragaria ×ananassa Duch. to Meloidogyne hapla Chitwood and Pratylenchus penetrans (Cobb) Filipjev & Shuurmans Stekhoven was evaluated in the greenhouse. Eleven genotypes were highly resistant to populations of M. hapla from Washington State and Oregon, with Rf values (initial nematode density/final population density) less than 0.5. However, root growth of most genotypes, including resistant genotypes, was reduced by M. hapla. Thirteen genotypes were ranked more resistant to P. penetrans than F. ×ananassa `Totem', a susceptible cultivar. Root growth of most genotypes was not affected by P. penetrans under these experimental conditions. We conclude that commercial cultivars and wild Fragaria genotypes can provide a readily exploitable source of resistance to M. hapla. Conversely, sources of resistance to P. penetrans were uncommon in the germplasm evaluated. The F. ×ananassa cultivars, which already have commercially important characteristics, appear to be a better source of resistance for both nematode species than the wild, unimproved germplasm.
Angela K. Anderson and Chad E. Finn
Trailing blackberry cultivars, such as `Marion', can be traced to relatively few chance selections of Rubus ursinus Cham. & Schlecht. Wild R. ursinus offer a range of horticulturally desirable traits to breeders, from high fruit quality to improved cold hardiness. Cuttings from 460 plants, representing 20 populations in southern British Columbia, Washington, and Oregon, collected in 1993. Rooted clones were planted in 1994 in a replicated field trial to assess morphological variation. A greenhouse study was also undertaken, with 10 clones represented from each site, in two replications. Preliminary data from the greenhouse and field studies show variability in the following morphological characters: Glandular hairs; cane and prickle color; cane diameter; prickle density; internode length; leaf color, size, shape and density; and senescent leaf drop and color change. Floricane morphology will be assessed in 1995. Analysis of these data will determine relative genetic distances among the populations and enhance the understanding of the diversity available in R. ursinus.
Patrick P. Moore and Chad E. Finn
Stan C. Hokanson and Chad E. Finn
Strawberry (Fragaria ×ananassa Duch.) cultivars used by commercial producers in North America often change rapidly due to several factors including modified cultural practices, processing and marketing practices, the desire for new cultivars with larger and higher quality berries, resistant insect and disease pests, loss of traditional chemical control methods, and private sector breeding programs. Within the past decade, the annual plastic-mulched production system has quickly expanded into eastern North America prompting the need for cold-hardy cultivars adapted to that system. The continuing loss of traditional chemical controls for strawberry insects and diseases, including the impending loss of methyl bromide, has prompted the need for increased insect and disease resistance. In addition, consumer demands for a healthier food product with lower chemical residues has heightened this need. Small fruit experts from across North America provided information on the primary strawberry cultivars used in the recent past, the present, and potential cultivars for the future, as well as on current strawberry acreage in their respective states and provinces.
Michael Dossett, Jungmin Lee and Chad E. Finn
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.