Penicillium fungi from Picea glehnii seeds protect the seedlings from damping-off

In a coinoculation test of seed-epiphytic Penicillium species and pathogeni c Pythium vexans to Picea glehnii seedlings, the number of surviving seedli ngs which were inoculated with P. vexans 5 d after preinoculation with Peni cillium damascenum PGS-O7 increased compared with those inoculated with P. vexans alone. The phytotoxicity of antifungal compounds to A glehnii seeds and seedlings was assessed in growth experiments, Production of these compounds was quant itatively analysed in the rhizosphere of the host seedlings using chromatog raphy techniques. Dense mycelial growth of P. damascenum was observed microscopically around the roots of the inoculated seedlings. Furthermore, the antifungal and phyt otoxic compound citrinin produced by P. damascenum was detected as a compon ent released around the roots of the normally growing fungus-inoculated see dlings. We propose two possible mechanisms for the protection of P. glehnii seedlin gs by P. damascenum from P. vexans; first, chemical protection by an antibi otic agent, citrinin produced by P. damascenum, and second, the occupation of the space around the P. glehnii roots by the P. damascenum mycelia. (C) New Phytologist (2001).