Canker and leaf scorch on olive (Olea europaea L.) caused by Neoscytalidium dimidiatum in Turkey

Abstract

In a recent survey of olive groves in the Southeast Anatolia Region of Turkey, a new and serious decline of olive trees, beginning with foliar scorching and then dieback of twigs, branches, and even whole trees, was observed for the first time. In more advanced stages of the disease, necrosis and cankers were observed on the bark of the trunk, branches, and twigs. Isolations from symptomatic tissues from multiple cultivars in diverse locations yielded Neoscytalidium dimidiatum, which were identified using ITS, tef1, and tub2 loci of genomic DNA, in combination with morphological data. In vitro studies showed that conidial germination, hyphal growth, and pycnidia formation of the pathogen were positively correlated with elevated temperatures. Wild type olive “Delice”, “Edincik Su”, and “Memecik” seemed like the most resistant cultivars on which disease severity values were the lowest among 14 screened olive cultivars in two experimental orchards under natural conditions. Pathogenicity tests showed that “Gemlik” was the most susceptible cultivar showing the largest cankers and extensive scorch lesions. Isolates caused canker but not leaf scorch on O. europaea cultivars “Arbequina” “Halhalı”, “Manzanilla”, “Nizip Yağlık”, and “Saurani”. Neoscytalidium isolates are likely to have a negative impact on the health of diverse olive groves, which are primarily confined to Mediterranean-type climatic regions. These findings suggest an increased risk of infection in environments with increasing temperatures, as is common in the Southeast Anatolia Region of Turkey. The information gathered in this study will be used to examine the disease's epidemiology and establish disease control initiatives. This is also the first report of N. dimidiatum infecting O. europaea in the world.