Cerato-ulmin (CU) presence was monitored on cell surface and
quantitatively 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 (races EAN and NAN) and, for the first time,
of
the weak Dutch elm disease pathogen O. ulmi and the
non-pathogen O. piceae. Quantitative determination of CU content
in
the mycelial extracts of the three species showed that high CU
cellular content is associated with high CU content in culture filtrates.
The
content of CU in biomasses and in culture filtrates was
influenced by temperature, growth phase and fungal species or race. CU
synthesis occurred during the stationary phase and in the
late logarithmic phase when fungi were grown at 23° and 32°C, respectively.
High temperatures of growth (32°) did not have a
negative effect on the cellular CU content but severely hampered CU secretion
in high CU-producers O. novo-ulmi isolates.