Identification and Characterization of Leaf Blight Caused by Botryosphaeria dothidea (Moug. Ex Fr.) Ces. & De Not. on Olive Tree (Olea europaea) in Adıyaman, Türkiye

The olive tree (Olea europaea L.), one of the oldest tree plants cultivated trees in the world, is a very important food crop, providing both oil and edible fruits. Most olive production takes place in Mediterranean countries, and Türkiye is one of the world’s leading olive-producing countries. In 2023, 1.5 million tonnes of olives were produced from 900,000 hectares of olive groves in Türkiye, while 4102 t of olives were produced from 3909 hectares of olive groves in Adıyaman in the same year. During the surveys in June 2021 and 2022, unusual leaf blight symptoms were observed on olive trees of the cultivar ‘Gemlik’ in various orchards in the province of Adıyaman in the Southeast Anatolian region of Türkiye. In severe cases, it causes early defoliation. Symptomatic leaves were collected from infected plants. Symptoms initially appeared as small brown spots with some yellow halos, but these became larger and darker with time. Infected leaf parts were disinfected with 1% sodium hypochlorite for 2 min, rinsed twice in sterile distilled water, dried on sterile filter paper and plated on potato dextrose agar (PDA) and incubated at 25–26 °C. Botryosphaeria dothidea was isolated from symptomatic olive leaves and identified by morphological and phylogenetic analysis of ITS‑1 and ITS‑4. Under controlled environmental conditions, detached leaves and seedlings of O. europea were subjected to inoculation experiments. Inoculation with a B. dothidea isolate produced typical symptoms of brown blight, and the same pathogen was re-isolated and identified. To the best of our knowledge, this is the first report of B. dothidea causing olive leaf blight in Türkiye.