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Characterization of Species of Diaporthe from Wood Cankers of Grape in Eastern North American Vineyards

July 2013 , Volume 97 , Number  7
Pages  912 - 920

Kendra Baumgartner and Phillip T. Fujiyoshi, Crops Pathology and Genetics Research Unit, United States Department of Agriculture–Agricultural Research Service (USDA-ARS), Davis, CA 95616; Renaud Travadon, Department of Plant Pathology, University of California, Davis; Lisa A. Castlebury, Systematic Mycology and Microbiology Laboratory, USDA-ARS, Beltsville, MD 20705; Wayne F. Wilcox, Department of Plant Pathology and Plant Microbe Biology, Cornell University, Geneva, NY 14853; and Philippe E. Rolshausen, Department of Plant Pathology and Microbiology, University of California, Riverside 92521

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Accepted for publication 18 January 2013.

In eastern North America, Phomopsis cane and leaf spot, caused by Phomopsis viticola, is a foliar disease of grape but, in the Mediterranean climate of western North America, P. viticola is primarily associated with wood cankers, along with other Diaporthe spp. To determine the identity of wood-infecting Diaporthe spp. in eastern North America, 65 isolates were cultured from 190 wood-canker samples from 23 vineyards with a history of Phomopsis cane and leaf spot. Identification of 29 representative isolates was based initially on morphology, followed by phylogenetic analyses of DNA sequences of the ribosomal DNA internal transcribed spacer region, elongation factor subunit 1-α, and actin in comparison with those of type specimens. Three species were identified: P. viticola, P. fukushii, and Diaporthe eres. Inoculations onto woody stems of potted Vitis labruscana ‘Concord’ and V. vinifera ‘Chardonnay’ showed that D. eres and P. fukushii were pathogenic (mean lesion lengths of 7.4 and 7.1 mm, respectively, compared with 3.5 mm for noninoculated controls) but significantly less so than wood-canker and leaf-spot isolates of P. viticola (13.5 mm). All three species infected pruning wounds of Concord and Chardonnay in the field. Our finding of pathogenic, wood-infecting Diaporthe spp. in all 23 vineyards suggests a frequent co-occurrence of the foliar symptoms of Phomopsis cane and leaf spot and wood cankers, although the latter are not always due to P. viticola.

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, 2013.