Evaluation of effect of Ophiostoma novo-ulmi on four major wood species of the elm family in Rasht (North West of Iran)

Dutch elm disease is the most common and destructive disease of the elm family. The pathogen of Ophiostoma novo-ulmi will systematically lead to the blockage of xylems and cavities, and will finally lead to the development of wilt symptoms. The present study aimed to compare the diameter size of vessels and the number of xylary rays in four species: Ulmus carpinifolia , Ulmus glabra , Zelkova carpinifolia and Celtis australis as important factors in host resistance to elm disease. To do this, some samples were randomly collected from 10 cm above the place of seedling’s inoculation. The test results showed that there was a significant difference at 1% probability level among the measured indicators in these four species, the maximum diameter of vessel and the maximum number of xylary rays belonged to U. carpinifolia . According to the results, Ulmus campestris was more sensitive towards Dutch elm disease as compared to the other three species, and C. australis had the greatest resistance to Dutch elm disease. Key words : Dutch elm disease, xylary rays, vessel, resistance.