Location: Horticultural Crops Disease and Pest Management Research Unit
Project Number: 2072-22000-045-071-A
Project Type: Cooperative Agreement
Start Date: Sep 1, 2026
End Date: Aug 31, 2027
Objective:
Oregon State University (OSU) hazelnut breeding program cultivars and pollinizers remain widely planted in the Willamette Valley, with ‘McDonald’ and ‘PollyO’ leading the kernel market. Eastern filbert blight (EFB) is the most damaging fungal disease of European hazelnuts. Oregon State University hazelnut breeding program develops high yielding EFB resistant hazelnut cultivars particularly for the blanched kernel market. A new EFB fungus race capable of overcoming predominantly used ‘Gasaway’ resistance was identified in Oregon in late 2023. The emphasis of EFB-resistance has been more focused on other single or pyramided sources of major resistance genes from European hazelnut and closely related species as well as quantitative resistance, which is more durable compared to single-gene-based resistance.
Objective 1. Develop hazelnut breeding populations through controlled crosses to produce new cultivars with resistance to EFB.
Objective 2. Inoculate hazelnut seedlings under controlled conditions to evaluate disease response and identify resistant individuals and new sources of resistance for breeding.
Objective 3. Develop, validate, and score DNA markers associated with EFB resistance to support marker-assisted selection.
Objective 4. Combine EFB resistance with high yield, nut and kernel quality, and other desirable horticultural traits to develop improved cultivars for commercial production.
Approach:
Controlled pollination will be conducted in the field among selected hazelnut parent trees with known traits for disease resistance, yield, and nut quality. Resulting hybrid nuts will be harvested, stratified under controlled cool and moist conditions, and germinated to produce seedlings. Seedlings will be planted and evaluated in the seedling blocks and replicated field trials for long-term evaluation of growth, yield, and horticultural performance.
For disease screening, seedlings will be inoculated with EFB spores in controlled greenhouse or under inoculation structure with diseased wood on top to ensure uniform exposure. At least 500 seedlings obtained from four different new sources of EFB resistance will be inoculated. Disease responses will be assessed in terms of number and size of the cankers to identify resistant and susceptible individuals. Available hazelnut genome sequence information will be used to identify candidate regions associated with EFB resistance. Leaf tissue samples will be collected form the hazelnut population showing segregation for the EFB disease resistance. DNA will be extracted and DNA markers linked to resistance genes will be developed and validated for use in selection.
For marker-assisted selection, leaf tissue will be collected from hazelnut seedlings derived from controlled crosses for DNA extraction. Molecular screening will be conducted using previously developed DNA markers to identify individuals carrying single or multiple EFB resistance genes. Seedlings not carrying any resistant genes will be discarded and selected resistant seedlings will be advanced in the breeding program.
Standard horticultural evaluation methods will be used to assess key traits such as yield, nut size, kernel quality, and plant vigor. 100 nut samples from each advanced selection will be evaluated for major defects, bleachability, and percentage kernel. Data from phenotypic and molecular screening will be combined to select elite genotypes that integrate EFB resistance with high yield and desirable nut quality for cultivar development.