Union Aberration of Sweet Cherry on Prunus mahaleb Rootstock Associated with X-disease. Jerry K. Uyemoto, USDA-ARS, Department of Plant Pathology, University of California, Davis 95616. . Plant Dis. 73:899-902. Accepted for publication 7 June 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/PD-73-0899.

Several sweet cherry (Prunus avium) scions, including cultivars Bing and Sam, on mahaleb roots (P. mahaleb) developed pits and grooves (aberration) in the wood at the union of the scion and rootstock a year after having been graft-inoculated with tissue from trees with symptoms of X-disease. Graft inoculations of Bing trees on Colt (P. avium × P. pseudocerasus) rootstock produced chronic X-disease symptoms consisting of small leaves and small fruit with short pedicels, but no union aberration. Several symptomatic indicator trees, but not healthy trees, were confirmed to contain X-disease mycoplasmalike organisms (XMLOs) by hybridization assay using a radioactive-labeled DNA probe specific for XMLO. Assays of X-diseased cherry trees for tomato ringspot virus by indirect ELISA and bud grafts onto P. tomentosa were negative.