2018 ASHS Annual Conference

Three hundred and eighty-three clonal accessions of Corylus were assessed for their response when exposed to eastern filbert blight (EFB, Anisogramma anomala) in New Jersey. The plants were deemed resistant or tolerant to EFB in previous studies and acquired from the U.S. Department of Agriculture Agricultural Research Service National Clonal Germplasm Repository, the University of Nebraska-Lincoln, the National Arbor Day Foundation, and Oregon State University. Further, clonal accessions derived from multiple seed introductions from across the native range of C. avellana in Europe and the Caucuses were included. The trees were planted in the field from 2004 to 2012 and subsequently exposed to EFB on a yearly basis. This study expands upon earlier work published in 2012 by examining disease progression over a longer time-period using additional genotypes. In January 2018, all trees were evaluated for presence of EFB. It was found that 207 of 383 accessions remained free of the disease. The 148 accessions with EFB present had their cankers measured and proportion of diseased wood calculated. Most noteworthy, ‘Ratoli’, a Spanish cultivar that carries a dominant R-gene, and all six of its selected offspring remained free of EFB across the span of this study. Further, all eight offspring of Yoder #5, a C. americana x C. avellana hybrid, also remained free of EFB, as did OSU 541.147, a C. americana x C. avellana hybrid related to C. americana ‘Rush’. Fifty-three of 65 new germplasm introductions selected at Rutgers and deemed resistant in earlier studies still remain free of EFB. In contrast, most accessions protected by the ‘Gasaway’ R-gene deteriorated with time. For instance, all ‘Zimmerman’ trees planted in 2005 were free of disease in 2012, whereas today five of the remaining six trees are infected. In addition, ‘Jefferson’ had its proportion of diseased wood increase from 4% to 31% and expresses larger individual cankers than recorded in 2012. Similarly, EFB increased on ‘Yamhill’ from 2% to 20%. Overall, most accessions from Oregon remained at least tolerant in New Jersey (proportion of diseased wood less than 25%), but only about a third remained free of EFB. Fortunately, more than 80% of the of the new introductions and nearly all C. fargesii, C. chinensis, C. heterophylla, and C. americana accessions continued to remain free of EFB. Generally, these results convey that a wide diversity of Corylus germplasm exists to support breeding efforts to combat this devastating disease.