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Occurrence of Togninia minima Perithecia in Esca-Affected Vineyards in California

Togninia minima is an important pathogen causing esca and grapevine declines worldwide. Although perithecia of T. minima have been produced in the laboratory, their presence in diseased vineyards has not been shown. In our study, perithecia of T. minima were found on grapevines in the field in five California counties. Perithecia were clustered on dead vascular tissue in deep cracks along trunks and cordons or on the surfaces of decayed pruning wounds. Field-collected perithecia were characteristic of T. minima perithecia previously produced in vitro and molecular sequence analysis of the internal transcribed spacer region of the nuclear ribosomal DNA additionally confirmed their identity. Ascospores from perithecia germinated on agar medium and formed colonies typical of T. minima. This is the first report of T. minima perithecia in diseased vineyards and suggests ascospores as an additional source of inoculum for new grapevine infections.