Characterization of Two Local Isolates of the Fungus Verticillium dahliae that Causes Vascular Olive Wilt, and the Reaction of Olive Cultivar Khudairi to Infection with this Pathogen

Muhrez, K.A. and B. Barhoum. 2024. Characterization of Two Local Isolates of the Fungus Verticillium dahliae that Causes Vascular Olive Wilt, and the Reaction of Olive Cultivar Khudairi to Infection with this Pathogen. Arab Journal of Plant Protection, 42(1): 1-8. https://doi.org/10.22268/AJPP-001219 This Study aimed to isolate and characterize two local isolates of the fungus Verticillium dahlia Kleb., Vd1 from Tal al-Tout region, Hama, and Vd2 from Al-Darouqiyat region, Lattakia, and assess their pathogenicity on Khudairi olive cultivar under artificial inoculation conditions. The fungal cultures of both isolates were circular with regular edges, with a white upper surface that turns black when microsclerotia are formed on day 12 of isolate Vd1 with a coverage rate of 70%, and on day 19 of isolate Vd2 with a coverage rate of 40%. The two isolates differed in biometric characteristics. 4-5 phialides branched from each conidiophore in isolate Vd1 and 4 in isolate Vd2. Microsclerotia produced were dark brown in color with an irregular spherical shape in both isolates with dimensions of 43.3x49.7 μm for isolate Vd1 and 32.1x39.3 μm for isolate Vd2. The disease reaction was evaluated on Khderi olive plants during 140 days after the artificial inoculation with both isolates. Isolate Vd1 caused 100% infection 50 days after artificial inoculation compared with 95 days for the isolate Vd2. The Area under the disease progress curve (AUDPC) indicated that the rate of disease progress in isolate Vd1 was about 1.5 times higher than that of isolate Vd2.