COMPARATIVE DETERMINATION OF CERATO-ULMIN ON CELL-SURFACE AND IN MYCELIAL EXTRACTS OF PATHOGENIC AND NONPATHOGENIC OPHIOSTOMA SPECIES

Cerato-ulmin (CU) presence was monitored on cell surface and quantitat ively determined in mycelial extracts of the elm pathogens Ophiostoma novo-ulmi (races EAN and NAN) and O. ulmi and of the non-pathogenic O. piceae. CU was detected on the surfaces of Ophiostoma novo-ulmi (race s EAN and NAN) and, for the first time, of the weak Dutch elm disease pathogen O. ulmi and the nonpathogen O. piceae. Quantitative determina tion of CU content in the mycelial extracts of the three species showe d that high CU cellular content is associated with high CU content in culture filtrates. The content of CU in biomasses and in culture filtr ates was influenced by temperature, growth phase and fungal species or race. CU synthesis occurred during the stationary phase and in the la te logarithmic phase when fungi were grown at 23 degrees and 32 degree s C, respectively. High temperatures of growth (32 degrees) did not ha ve a negative effect on the cellular CU content but severely hampered CU secretion in high CU-producers O. novo-ulmi isolates.