Morphological and ecological variation of Gremmeniella abietina var. abietina in Pinus sylvestris, Pinus contorta and Picea abies sapling stands in northern Finland and the Kola Peninsula

The morphological and ecological variation of two types of Gremmeniella abi etina var. abietina causing scleroderris canker on conifers was investigate d in Pinus spp. and Picea sp. sapling stands in northern Finland and the Ko la Peninsula. Small-tree type (STT or B type) of G. abietina was detected a lone in 13 Scots pine, three lodgepole pine and two Norway spruce sapling s tands out of 26 stands investigated, both STT and large-tree type (LTT or A type) were observed in six Scots pine stands, and LTT was detected alone i n two Scots pine stands. For the first time, G. abietina was found to injur e Norway spruce saplings in a respective plantation in northern Fennoscandi a. STT isolates produced statistically significantly more conidia in vitro than LTT isolates. Morphological variation in conidia septation revealed th at STT produced conidia with more than five septa more frequently than did LTT. There was a greater range in variation in septation in STT than in LTT , with overlapping between the types. Isolates of both types were equally a ssociated with cankers, coloured wood, pycnidia or apothecia in the infecte d saplings.