Occurrence and Importance of Chaetomium globosum as a Fungal Pathogen on Olive Leaves in Adıyaman Province of Türkiye

The olive (Olea europaea L.), one of the oldest cultivated plants in the world, is one of the perennial plants of the Oleaceae family. The majority of production takes place in Mediterranean countries, and Türkiye is one of the world’s leading olive producing countries. In 2023, 1.5 million t of olives were produced from 900,000 hectares of olive groves in Turkey, and 4102 t of olives were produced from 3909 hectares of olive groves in Adıyaman province in the same year. In the study carried out to determine the diseases of ‘Gemlik’ variety olive trees in these areas, samples were taken from the leaves of olive trees showing disease symptoms in June in 2021 and 2022 and sent to the laboratory. Following the isolation studies carried out to determine the causes of the symptoms on the leaves of diseased olive trees showing leaf spot symptoms, the development of Chaetomium-like colonies was observed. Pathogenicity studies carried out under in vitro conditions showed that the isolate obtained was an olive leaf pathogen. Microscopic examinations and molecular diagnostic studies identified the pathogen as Chaetomium globosum. C. globosum colonies developed rapidly and acquired a cottony appearance. Additionally, in PDA medium, the colony, which initially had a whitish appearance, changed over time from tan to reddish brown. C. globosum is a fungus whose biocontrol effects have been widely studied. It has been reported as a pathogen of various host plant species and has spread worldwide. To the best of our knowledge, this study is the first report on leaf spot caused by C. globosum as a pathogen on olives in Türkiye.