North America where hazelnuts are now grown as well as those regions suitable for future production. Therefore, the identification and development of cultivars resistant to the disease is a necessary objective of hazelnut breeding programs in North
present throughout the entire hazelnut-producing area in Oregon. GERMPLASM IMPROVEMENT Oregon State University's Hazelnut Breeding Program run by Dr. Shawn Mehlenbacher responded to the threat of EFB by developing EFB-resistant cultivars. The breeding
‘Gasaway’, controlled by a dominant allele at a single locus ( Mehlenbacher et al., 1991 ), has been extensively used in the hazelnut breeding program at OSU. Most advanced selections and recently released cultivars and pollenizers carry ‘Gasaway
’, conferred by a dominant allele at a single locus ( Mehlenbacher et al., 1991 ), has been extensively used in the hazelnut breeding program at Oregon State University (OSU). Most resistant selections from the breeding program carry ‘Gasaway’ resistance. In
University hazelnut breeding program carry this resistance. Recent hazelnut releases including ‘Jefferson’, ‘Yamhill’, ‘Dorris’, ‘Wepster’, and ‘McDonald’, the pollinizers ‘Eta’, ‘Theta’, ‘York’, and, ‘Felix’, and the ornamentals ‘Red Dragon’ and ‘Burgundy
Hazelnuts in Oregon are grown on 30,000 acres by ≈1000 orchardists in the Willamette Valley. Their annual production accounts for 3% to 5% of the world's hazelnut tonnage. The trees are grown in a single trunk system wrtb an average spacing of 20 feet between trees. Mechanical harvestihg is done in October. The industry employs an Integrated Pest Management approach, utilizing combinations of scouting, trapping, and biological control. The main insect pests are filbertworm, filbert leafroller, obliquebanded leafroller, and filbert aphids. The aphid parasite Trioxys pallidus was imported from Europe and successfully established in Oregon. Eastern Filbert Blight, Anisogramma anomala, a fungus disease, is the most serious disease problem in the industry. Annual applications of nitrogen to the soil and boron applied to the foliage are routine for Oregon's hazelnut growers. OSU research has quantified the importance of good light distribution in the tree canopy for increased nut production. OSU recommends a 5-year rotational pruning program. Some growers use mechanical hedging instead of hand pruning. OSU is home to the world's largest hazelnut breeding program. `Barcelona' is still the main, cultivar grown, while `Ennis' is the main in-shell variety. There is growing interest in planting varieties with a high percent kernel, such as `Casina', `Willamette', and `Lewis'.
scouting, pruning, and spraying to control this disease ( Mehlenbacher, 1995 ). The resistance from ‘Gasaway’, an obsolete pollinizer ( Mehlenbacher et al., 1991 ), has been extensively used in the hazelnut breeding program at Oregon State University (OSU
goal of the Oregon State University (OSU) hazelnut breeding program. Complete resistance to EFB was first discovered in the obsolete pollinizer ‘Gasaway’ ( Cameron, 1976 ). Genetic studies showed that complete resistance is conferred by a single
Giffoni’, ‘Tonda Romana’ ( Manzo and Tamponi, 1982 ), and ‘Tonda Italiana’ from Italy (this last one, an IRTA selection from Italian material); and ‘Clark’, ‘Lewis’, and ‘Willamette’ from the hazelnut breeding program at OSU ( Mehlenbacher et al., 1991
to take notes on the trees and comment as to which were more desirable. These comments supplemented the notes recorded by the hazelnut breeding program (S.A. Mehlenbacher and D.C. Smith). Fig. 1. Pedigree of ‘Red Dragon’ ornamental hazelnut