ISHS Acta Horticulturae 556: V International Congress on Hazelnut
THE ‘OREGON HAZELNUT STUNT SYNDROME’ AND PHYTOPLASMA ASSOCIATIONS |
| Authors: | J.D. Postman, K.B. Johson, J.L. Maas, R.E. Davis |
| Keywords: | disease, Corylus avellana, symptoms, DNA, RFLP |
| Abstract:
A stunt syndrome was first observed in several commercial hazelnut (Corylus avellana L.) orchards in northwest Oregon during the late 1950’s. The disease is of minor importance, since the affected areas have been small and isolated and the spread has been very slow. Severely affected trees become slightly chlorotic with reduced leaf size, reduced internode length, insignificant nut production and dieback of small branches. The disease agent has been transmitted to healthy hazelnut rootstocks by grafting. Removal of diseased trees and adjacent trees can eliminate the disease from an orchard. Failure to remove trees adjacent to infected trees resulted in the eventual spread throughout about 4 ha of a 20 ha orchard, apparently by root grafting. Leaf samples from infected trees were assessed for phytoplasma infection by nested polymerase chain reactions for amplification of 16S ribosomal DNA sequences. Restriction fragment length polymorphism patterns indicated the presence of clover yellow edge phytoplasma (16SrIII-B) and another phytoplasma, putatively a member of a new subgroup in the X-disease group (16SrIII). Phytoplasmas were detected in stunted as well as in nearby symptomless field trees, but not in greenhouse grown trees. All phytoplasmas detected in Oregon were different from those reported to be associated with decline and yellows disorders of hazelnut in Germany and Italy. | |
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