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Title: Characterization of Cytospora isolates from wood cankers of declining grapevine in North America, with the descriptions of two new Cytospora species

Author
item Lawrence, Daniel
item TRAVADON, RENAUD - US Department Of Agriculture (USDA)
item POUZOULET, JEROME - University Of California
item ROLSHAUSEN, PHILIPPE - University Of California
item WILCOX, WAYNE - Cornell University
item Baumgartner, Kendra

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2016
Publication Date: 5/9/2017
Citation: Lawrence, D.P., Travadon, R., Pouzoulet, J., Rolshausen, P.E., Wilcox, W.F., Baumgartner, K. 2017. Characterization of Cytospora isolates from wood cankers of declining grapevine in North America, with the descriptions of two new Cytospora species. Plant Pathology. 66(5):713-725. DOI 10.1111/ppa.12621.

Interpretive Summary: A group of fungi that cause the disease Cytospora canker on numerous woody tree species (e.g., stone fruits, Eucalyptus trees) were isolated from diseased grapevines. The species Cytospora chrysosperma, C. cincta, and C. leucostoma have been reported from grapevines showing symptoms of one or more trunk diseases (Esca, Botryosphaeria-, Eutypa-, and Phomopsis dieback), none of which are known to be caused by or associated with Cytospora species, but instead by unrelated fungi, such as Phaeomoniella chlamydospora, Phaeoacremonium minimum, Neofusicoccum parvum, Eutypa lata, and Diaporthe ampelina. To understand the role of members of Cytospora in the grapevine trunk-disease complex, 21 Cytospora isolates were collected from discolored wood of grapevines eastern North America vineyards in seven states and two Canadian provinces. We identified two new species: Cytospora vinacea sp. nov. and Cytospora viticola sp. nov. When tested as pathogens in the greenhouse, both species were pathogenic based on development of the same symptoms we saw in the vineyards (dead shoots, stunted shoots, dead fruiting positions on the grapevine arm). Under the microscope, cultures of these two species are distinguishable based on the color of the culture and the size of the spores. This study represents the first attempt to characterize Cytospora species associated with grapevine trunk diseases in eastern North America.

Technical Abstract: Cytospora species are ubiquitous pathogens of woody plants, causing dieback and wood cankers in numerous perennial hosts, including agronomic crops (e.g., Prunus), timber trees (e.g., Eucalyptus), and riparian hosts (e.g., Salix). Cytospora chrysosperma, C. cincta, and C. leucostoma have been reported from grapevines showing symptoms of one or more trunk diseases (Esca, Botryosphaeria-, Eutypa-, and Phomopsis dieback), none of which are known to be caused by or associated with Cytospora species, but instead by other ascomycetes such as Phaeomoniella chlamydospora, Phaeoacremonium minimum, Neofusicoccum parvum, Eutypa lata, and Diaporthe ampelina. To understand the role of members of Cytospora in the grapevine trunk disease complex, 21 Cytospora isolates were collected from discolored wood of Vitis vinifera and Vitis hybrids, from eastern North America vineyards in seven states and two Canadian provinces. Phylogenetic analyses of ITS and translation elongation factor 1-a identified two novel species: Cytospora vinacea sp. nov. and Cytospora viticola sp. nov. When inoculated to the woody stems of potted V. vinifera ‘Thompson Seedless’ in the greenhouse, both species were pathogenic based on development of wood lesions and fulfillment of Koch’s postulates. Cytospora viticola was more virulent, producing the largest lesions, 17.3 mm, on average, at 12 months post-inoculation. Morphological comparisons of these two species revealed that they are distinguishable, based on cultural and conidial dimensions; C. vinacea produced a distinct vinaceous colony and shorter conidia, 5.2 µm, on average. This study represents the first attempt to characterize Cytospora species associated with grapevine trunk diseases in eastern North America.