Interactions between Cylindrocarpon destructans and ectomycorrhizas of Picea abies with Laccaria laccata and Paxillus involutes

Summary In paired cultures with two mycorrhizal fungi, the root pathogen Cylindrocarpon destructans (Zinsm.) Scholten had an inhibitional effect on mycelial growth of Laccaria laccata (Scop, ex Fr.) Bk. & Br. but was inhibited itself by Paxillus involutes (Batsch.) Fr. A similar pathogen-symbiont interaction scheme was observed in triaxenic cultures with Picea abies Karst. seedlings but only in the vicinity of the mycorrhizal root tips. Both mycorrhizas similarly increased the endogenous plant resistance against the infection of C. destructans. This suggests that direct pathogen-symbiont interactions are an important factor for population dynamics in the mycorrhizo sphere. Moreover, endogenous plant resistance constitutes one of the key factors for an effective defence against pathogenic fungi.