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Line Pattern of Birch Caused by Apple Mosaic Virus. A. R. Gotlieb, Research Assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706; J. G. Berbee, Professor of Plant Pathology and of Forestry, University of Wisconsin, Madison 53706. Phytopathology 63:1470-1477. Accepted for publication 16 May 1973. DOI: 10.1094/Phyto-63-1470.

Fifteen white birch and 12 yellow birch trees were graft-inoculated with budwood from a white birch tree displaying line pattern and ringspot symptoms on scattered leaves. Within 2 years, one-third of the white birch and two-thirds of the yellow birch trees exhibited line pattern symptoms. Remission of all leaf symptoms in the continued presence of the virus usually occurred thereafter. A virus from the white birch tree that supplied the budwood was mechanically transmitted to cucumber, squash, cowpea, and bean plants. The birch virus was purified from infected cucumber cotyledons by differential centrifugation. It was identified as apple mosaic virus (ApMV) on the bases of symptoms in selected herbaceous hosts, serological relationships, virus components, and virus morphology. Cucumber proved to be a highly efficient and reliable host for indexing both white and yellow birch trees for ApMV. The virus also was detected consistently in the crude leaf sap of infected white and yellow birch trees by Ouchterlony gel double-diffusion tests.