Somatic compatibility in Amylostereum areolatum and A. chailletii as a consequence of symbiosis with siricid woodwasps

Somatic compatibility is used to identify clones or vegetative compatibilit y groups (VCG) in fungal populations. For basidiomycetes, VCGs have normall y been associated with either homothallic, non-outcrossing fungi or root de cay fungi spreading by vegetative growth. A special instance is provided by the symbiotic relationships between woodwasps and the fungi Amylostereum a reolatum and A. chailletii. This association results in clonal propagation, as the wasps (Sirex sp. and Urocerus sp.) transfer arthrospores of A. areo latum or A. chailletii during ovipositing in conifers. Identical isolates o f the symbiont are normally carried by all the female offspring of one wasp . The presence of clones of A. areolatum and A. chailletii was tested throu gh somatic compatibility shown in pairings of heterokaryons obtained from w asps, basidiocarps and wood. Isolates found more than 100 km apart within D enmark belonged to the same vegetative compatibility groups. In addition, A . areolatum isolates from Sweden and Lithuania were compatible with a Danis h clone, in spite of the barrier of the Baltic Sea. The association between woodwasps and fungi thus creates dispersive clones or VCGs which are stabl e across time and space. The dispersal through basidiospores may be conside red of less importance for A. areolatum, but common in A. chailletii.