Variations in symbiotic efficiency, phenotypic characters and ploidy level among different isolates of the ectomycorrhizal basidiomycete Laccaria bicolor strain S 238

Age and maintenance conditions of pure cultures of ectomycorrhizal fungi during culture storage can affect their ploidy level, their symbiotic potential and their efficiency on host development. The symbiotic efficiency and the fructification potential of seven isolates of Laccaria bicolor obtained from a single basidiome were examined. Even after 18 yr of repeated sub-culturing on agar media without any passage through a compatible host, e.g. Douglas fir or spruce, three dikaryotic isolates were able to form mycorrhizas and to increase Douglas fir seedlings' growth. Although the seven isolates gave identical banding patterns after restriction enzyme digestion of the mitochondrial small rDNA and the ITS region and IGS1 region of the ribosomal nuclear DNA they exhibited strong differences in mycelial growth in pure culture and in fructification rate when associated with Douglas fir. Date and intensity of fructification, and size and features of basidiomes were affected suggesting that the sub-culturing altered gene expression or gene organization.