Variation in nitrogen source utilisation by Pisolithus isolates maintainedin axenic culture

The influence of various inorganic and organic nitrogen sources on biomass production by 17 isolates of Australian Pisolithus spp. was investigated be fore and after a 3-year maintenance period in axenic culture. While some is olates produced similar or higher amounts of biomass on NH4+ or certain ami no acids after the maintenance period, there was a general trend to reduced biomass production on these substrates. Biomass production by most isolate s on bovine serum albumin increased significantly after maintenance. The da ta are discussed in relation to the use of axenic culture growth experiment s for investigations of inter- and intraspecific physiological variation il l ectomycorrhizal fungi.