Analyzing the histopathology of the olive inoculated with Verticillium dahliae

Verticillium wilt is one of the most important vascular diseases of olive. For this reason, investigating different aspects of this disease such as distribution, biology, pathogenicity, and disease management have always been considered significant. In an attempt to investigate host-pathogen interaction, the present experiment was carried out to study the histopathology of olive (cultivar Zard) inoculated by Verticillium dahliae. Root-dipping method for 30 minutes was used for the inoculation of the seedlings by spore suspension with concentration 109 spore/ml. Four to twelve weeks after inoculation, with the 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 the microscopic investigations indicated that the causal agent of Verticillium wilt has caused disorders in the physiology through spreading into vessels, obstruction of xylem vessels, and their destruction. The casual agent also resulted in disorder in the flowing of vascular sap and caused shoot wilt. The results indicated that the seedlings obstructed the vessels and prevented the spread of pathogen with producing tylose. The pathogenicity and defensive mechanisms associated with host-pathogen interaction and their roles in susceptibility rate of the olive to Verticillium wilt have been discussed in this research.