Disease Note.

Occurrence of Grapevine Yellows in Virginia Vineyards. T. K. Wolf, Virginia Agricultural Experiment Station, Winchester 22601. J. P. Prince and R. E. Davis, USDA-ARS Molecular Plant Pathology Laboratory, Beltsville, MD 20705. Plant Dis. 78:208. Accepted for publication 13 October 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0208C.

This is the first description of a yellows disease of grapevine (Vitis vinifera L.) in Virginia; the disease has been observed on cvs. Chardonnay and Riesling since 1987. Symptoms include abortion and withering of flower clusters, shoot tip dieback, downward curling of leaves, leaf chlorosis, and premature leaf abscission. Leaf chlorosis is either generalized or confined to tissues adjacent to major veins and may be accompanied by necrosis. Affected shoots droop and have regions where periderm fails to mature. Diseased vines do not recover and often die within several years of symptom onset. The disease has been observed in at least 12 Chardonnay and three Riesling vineyards throughout the Virginia Piedmont. The incidence and rate of spread in a given vineyard are generally low. For example, new cases of symptomatic vines in a 2,100-vine Chardonnay vine- yard were 2 in 1988, 9 in 1991, and 16 in 1992. During the 1992 and 1993 growing seasons, DNA was extracted from tissue samples collected from at least 40 individual vines exhibiting symptoms in four different vineyards. The DNA samples were analyzed for the presence of mycoplasmalike organism (MLO) DNA by use of the polymerase chain reaction in which reaction mixtures contained synthetic oligonucleotides designed to prime specific amplification of MLO DNA. Template DNAs from approximately one-half of the symptomatic vines yielded MLO-specific DNA amplification products. Use of varied primers and restriction analyses of amplified DNAs indicated that the MLOs detected in diseased vines belonged to no less than two distinctly different MLO genomic groups (2). The DNA analyses and field observations indicate a possible similarity of the Virginia grapevine yellows disease to the grapevine flavescence doree reported in Europe (1).