In vivo INTERACTION OF Verticillium dahliae, THE CAUSAL AGENT OF PISTACHIO VERTICILLIUM WILT, WITH Acremonium kiliense*

This study was conducted on the interaction between Verticillium dahliae, the causal agent of vascular wilt of pistachio trees, and Acremonium kiliense, an endophyte fungus with biological control effects. Nine-month-old seedlings of three pistachio cultivars including Sarakhs, Badami-Rize-Zarand and Ghazvini were used by root dip method in conidial suspension (10⁶ ml^-1) and transferred to pots containing autoclaved soil. After one month, the inoculated seedlings were transferred to soil containing 40 microsclerotia/g soil of V. dahliae. The trial was performed as a two-factor factorial experiment with 3 replications for each combination, the factors being cultivars and fungal treatments at 3 and 4 levels, respectively, in a completely randomized design. The results showed an increase in the dry weight of roots and shoots in trees inoculated with A. kiliense plus V. dahliae compared to trees inoculated only with V. dahliae. Interaction of A. kiliense and V. dahliae decreased the percentage of shoots and roots infection compare to treatments of V. dahliae alone. The percentage of V. dahliae isolation from different treatments showed that cultivars inoculated with A. kiliense plus V. dahliae had a lower colonization by V. dahliae than those inoculated only with V. dahliae. The results of statistical grouping revealed that shoot dry weight in all inoculated cultivars with A. kiliense, A. kiliense plus V. dahliae, and control belonged to one group, whereas cultivars inoculated only with V. dahliae constituted a separate group. The results of the Verticillium isolation from tissue showed that the isolation rate of V. dahliae in interaction between A. kiliense-V.dahliae, compared to V. dahliae alone, decreased  more than 50 percent in all cultivars.