A survey on histopathology of olive inoculated by Verticillium dahliae

Verticillium wilt is one of the most important vascular diseases of olive. It has always being considered to survey its various aspects such as distribution, biology, pathogenicity and management. In order to investigate host-pathogen interaction, this research was carried out to study histopathology of olive (cultivar Zard) inoculated by Verticillium dahliae. Rootdipping method for 30 min was used for inoculation of the seedlings by spore suspension with concentration 109 spore/ml. 4-12 weeks after inoculation, with occurrence of wilt symptoms; transversal sections were prepared from various parts of the stem and root. Then, very thin transversal sections were prepared and after different stages of staining, microscopic slides were prepared. The results of microscopic investigations showed that the causal agent of Verticillium wilt has caused disorders in physiology and flowing of vascular sap through spreading into vessels, obstruction of xylem vessels and their destruction. The results also showed that seedlings with producing tylose caused obstruction of vessels and prevented spreading of pathogen. Pathogenicity and defensive mechanisms associated with host-pathogen interaction and their roles at susceptibility rate of olive to Verticillium wilt had been discussed in this research.