Variable response of eastern filbert blight resistance sources in New Jersey

Area of Science:

• Plant Pathology
• Horticulture
• Genetics

Background:

• Eastern filbert blight (EFB) is a major constraint on hazelnut production in the U.S.
• Resistance to EFB is crucial for commercial viability.
• Current resistance strategies often rely on specific resistance (R) genes.

Purpose of the Study:

• To evaluate EFB resistance of hazelnut cultivars and selections in New Jersey.
• To compare EFB responses between Oregon and New Jersey to identify potential pathogen variation.
• To assess the durability and effectiveness of different EFB resistance sources.

Main Methods:

• Field planting of 82 EFB-resistant/tolerant hazelnut cultivars/selections in New Jersey.
• Documentation of disease incidence, severity, stem cankers, and diseased wood proportion.
• Evaluation of resistance linked to specific linkage groups (LG2, LG6, LG7) and quantitative resistance (QR).

Main Results:

• Significant divergence in EFB response between Oregon and New Jersey, indicating pathogen variation.
• Most LG6-linked resistance, including 'Gasaway' allele, failed in New Jersey (87% infection).
• EFB observed on LG7-linked resistance from 'Ratoli' origin; other LG7 and LG2 resistances were effective. QR responses were consistent across locations.

Conclusions:

• Pathogenic variation in *Anisogramma anomala* challenges reliance on single R-genes for EFB management.
• LG6 resistance, critical for the U.S. industry, shows limited durability.
• Quantitative resistance (QR) may offer more stable EFB resistance across diverse pathogen populations.