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Choke Disease Caused by Epichloë bromicola in the Grass Agropyron repens in Poland

Agropyron repens (synonym Elymus repens, couch grass) is a species native to Europe and Asia. In Poland, it is a common weed of crop fields. In May 2008, we noticed for the first time symptoms of choke disease (caused by Epichloë spp.) on A. repens at two localities in central Poland. The localities, Pakość (52°47.531′N, 18°06.118′E) and Dulsk (52°45.329′N, 18°20.518′E), are located 16 km apart from each other. The following year, we confirmed the occurrence of choke disease on couch grass at these localities. Stromata were formed on reproductive stems that did not produce inflorescences. They ranged from 16 to 31 mm long and were covered with perithecia 520 to 560 × 160 to 250 μm at a density of 35 to 45 per mm². Asci measured 270 to 310 × 5.2 to 6.5 μm and ascospores were 225 to 275 × 1.5 to 1.7 μm (specimen deposited in ZT). Morphological characters match with the original description of Epichloë bromicola (4). One strain was isolated from stromatal tissue and the partial DNA sequence of tubB including introns 1 to 3 was obtained as previously described (2). In a phylogenetic analysis, the isolate (GenBank Accession No. GU325782) grouped with Epichloë isolates from other Agropyron spp. from Poland (A. intermedium) and Japan (A. ciliare and A. tsukushiense) and with an isolate from a Roegneria sp. (from China). Experimental mating tests involving isolates from A. intermedium and a Roegneria sp. indicated that these isolates were sexually compatible with Epichloë bromicola from Bromus erectus. Similarly, E. yangsii was compatible with E. bromicola. This suggests that Epichloë isolates from Agropyron, Roegneria, and Bromus hosts form a common mating population, and implies that under a biological species concept the phylogenetic definition of E. bromicola has to be broadened. Epichloë on A. repens has been previously found in Poland (1), Germany (3), Hungary, and Romania (specimen deposited in herbarium of ETH Zurich, ZT) based on incidental records or on herbarium specimens that have been listed under E. typhina. Our study, based on morphology, tubB sequence similarity, and mating compatibility, suggests that the fungus infecting A. repens in Poland is E. bromicola.

References: (1) I. Adamska. Acta Mycol. 36:31, 2001. (2) D. Brem and A. Leuchtmann. Evolution 57:37, 2003. (3) J. Kohlmeyer and E. Kohlmeyer. Mycologia 66:77, 1974. (4) A. Leuchtmann and C. L. Schardl. Mycol. Res. 102:1169, 1998.