First Report of Sclerotinia Stem Blight Caused by Sclerotinia trifoliorum on Trifolium ambiguum in Poland

Kura clover (Trifolium ambiguum M. Bieb.), a rhizomatous, persistent legume native to the Caucasus region, has received recent attention in North America and New Zealand as a pasture and silage crop. It is reported to be resistant to most pathogens affecting other clovers, including Sclerotinia trifoliorum Eriks. (3,4), one of the most destructive pathogens of clovers in northern Europe. Kura clover (cv. KTA202) was established in May 2009 near Mochelek, Poland (53° 13′ N, 17° 51′ E) on a Luvisol soil. By May 2011, 70% of plants grown in an experimental field (350 m2) had died, and 20% of the remaining plants were yellow and wilted. At crowns and the lower stem regions, wet, brown lesions with delicate white mycelium were observed. Lesion development was followed by death of the entire plant in a few days. By early June, only a few asymptomatic plants per square meter remained in the field. Tissue fragments of 20 symptomatic plants were surface-sterilized with 1% NaOCl for 1 min and plated on potato dextr...