The 2012 ASHS Annual Conference

Over 190 clonal accessions of Corylus L., including species and various interspecific hybrids of C. avellana L., C. americana Marshall, C. heterophylla Fisch., C. colurna L., and C. fargesii (Franch.) C.K. Schneid were assessed for their response to the eastern filbert blight (EFB) pathogen, Anisogramma anomala (Peck) E. Müller, in New Jersey, where the fungus is native.  Plants were obtained from the USDA–ARS National Clonal Germplasm Repository and Oregon State University, both in Corvallis, Oregon, the University of Nebraska, Lincoln, and the National Arbor Day Foundation. Plants were also acquired from the Morris and Holden Arboreta and from nurseries in Amherst, New York and Niagara-on-the-Lake, Ontario, Canada.  Accessions were chosen based on their resistance to EFB in Oregon, a region where A. anomala is not native, or anecdotal reports suggesting resistance to the disease.  Trees were planted in the field from 2002 through 2009 where they were exposed to EFB yearly through field inoculations and natural spread.  In January 2012, they were evaluated for the presence of EFB.  Cankers were measured and the proportion of diseased wood was calculated for susceptible trees.  Results showed most accessions reported to be resistant to EFB in Oregon maintained a useful level of tolerance in New Jersey, with a number remaining free of disease.  However, several accessions developed small to medium-size cankers and showed branch die-back, including offspring of C. avellana ‘Gasaway’.  Most C. americana and C. heterophylla accessions remained free of EFB, although variation in EFB response was found in hybrids of these species with C. avellana.  Nearly half of the C. colurna × C. avellana hybrids developed cankers, while all C. fargesii accessions and most grower selections developed in eastern North America remained free of EFB.  The results document the existence of a wide diversity of Corylus germplasm that expresses resistance or tolerance to EFB in New Jersey and confirms previous reports that C. americana is resistant to the disease.  Interestingly, most C. heterophylla and all C. fargesii were also found to be resistant, despite originating in Asia where A. anomala is absent.  The various interspecific hybrids show the potential for incorporating EFB resistance from wild species through breeding.  The results provide further evidence of differences in disease expression in Oregon and New Jersey, where isolates differ and disease pressure may be higher.