the involvement of cerato-ulmin toxin on pathogenicity and survive of ophiostoma ulmi and o. novo-ulmi fungi, causal agents of dutch elm disease

cerato-ulmin is the most important toxin of fungal causal agents of dutch elm disease and its content is one of the most important factors to distinguish two species ophiostoma ulmi and o. novo-ulmi. with attention to the ophiostoma novo-ulmi is more pathogenicity than o. ulmi, this research was carried out to discuss the role of cerato-ulmin on pathogenicity of causal agent using measurement of cerato-ulmin content of isolates of casual agent and their comparison with pathogenicity and spore germination ability in moisture stress conditions. for these aim, content of cerato-ulmin toxin was calculated as cerato-ulmin production index (cpi) using spectrophotometer at 400 nm. the spore germination was also calculated in moisture stress conditions (5, 10 and 15 days-old). the results showed that o. novo-ulmi isolates able to produce the higher cerato-ulmin toxin than o. ulmi, however was not observed clear relationship between rate of defoliation and wilting of ulmus glabra huds. seedlings and toxin production but there was completely significant positive correlation between rate of spore germination in moisture stress conditions and toxin production by fungal isolates of dutch elm disease. the involvement of cerato-ulmin on pathogenicity of causal agents of dutch elm disease is intricate.