Abstract
Four fungi isolated from trunks and branches of European hazelnut (Corylus avellana L.) from commercial orchards in the Willamette Valley, Oregon were characterized and pathogenicity was tested on potted hazelnut trees. The acreage of hazelnuts in Oregon has expanded greatly in recent years in response to the availability of Eastern filbert blight resistant cultivars. Fungi were characterized using the BLASTn algorithm and the GenBank database with multiple partial gene sequence(s). If BLASTn and GenBank were not sufficient for species-level identification, then a multilocus sequence analysis (MLSA) was performed. The four pathogens were identified as Diplodia mutilla (Fr.) Mont., Dothiorella omnivora B.T. Linaldeddu, A. Deidda & B. Scanu, Valsa cf. eucalypti Cooke & Harkn., and Diaporthe eres Nitschke. All pathogens but D. omnivora have not been previously reported from European hazelnut in the literature. All four pathogens caused lesions on trunks bare root hazelnut trees cv. ‘Jefferson’ planted in pots in the greenhouse and fungi were re-isolated from inoculated trees. D. mutilla appeared particularly aggressive in repeated inoculation experiments.
Highlights
The US production of European hazelnut (Corylus avellana L.) occurs almost exclusively (>98%) in Oregon’s Willamette Valley, which has an ideal climate and suitable soils for production
A. anomola is endemic to C. americana Walt., one of three native North American hazelnut species that is common across the Midwestern US and East Coast
Symptomatic plant material showing stem and trunk cankers was collected from commercial hazelnut orchards in the Willamette Valley, OR during the 2016 and 2017 growing seasons and brought to the Oregon State University Plant Disease Clinic in Corvallis, OR
Summary
The US production of European hazelnut (Corylus avellana L.) occurs almost exclusively (>98%) in Oregon’s Willamette Valley, which has an ideal climate and suitable soils for production. The hazelnut industry in the Pacific Northwest, which once represented substantial acreage in western Washington and British Columbia, had been in a decades-long decline because of the devastating effects of the adventive fungal pathogen Anisogramma anomola (Peck). A. anomola is endemic to C. americana Walt., one of three native North American hazelnut species that is common across the Midwestern US and East Coast. A. anomola is a minor pathogen, but on European hazelnut it causes the devastating disease known as Eastern filbert blight (EFB). Symptoms of the disease include branch dieback and perennial cankers that can kill the tree if they are not removed [1,2,3]. Pruning of cankers during winter and spraying of fungicides from bud break through shoot
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