Pistacia lentiscus var. chia (Anacardiaceae) is a small evergreen tree or shrub, up to 4 m in height, and distributed in the Mediterranean region up to 700 m above sea level. In Turkey, it is found throughout the Aegean and Mediterranean geographical regions. Mastic gum is an essential oil obtained from leaves, fruits or trunk exudate, used for the relief of upper abdominal discomfort, stomach aches, dyspepsia and peptic ulcer. The aerial parts of the plant have been used as a popular cure for hypertension. The oil has been used in the perfumery, food and pharmaceutical industries, and is currently being evaluated as a flavouring in alcoholic beverages and chewing gum (Kıvçak & Akay, 2005). In recent years, afforestations of this species in the coastal region of Western Anatolia have been severely affected by dieback and tree mortality. Symptoms included shoot and twig dieback, necrotic lesions and cankers in the bark as well as discolouration of the wood. In spring 2009, Pestalotiopsis guepinii was consistently isolated from small necrotic lesions on shoots of diseased P. lentiscus var. chia saplings in this area and from diseased seedlings in a nursery located in Karşıyaka district, İzmir, Turkey.
Mycelial growth on potato dextrose agar (PDA) was cottony white and conidia were produced in ink-like fruiting bodies. After 2 weeks, acervular conidiomata (up to 200 μm in diameter) developed on the infected shoots incubated at 100% relative humidity and 20–24°C, and in cultures grown on PDA at 24°C. All isolates had 5-celled smooth conidia. Apical and basal cells were hyaline, cylindrical to conic. The three intermediate cells were dark brown, with the two upper ones sometimes darker. Conidia were 22·8–29·1 μm × 5·3–8·9 μm. There were typically three apical appendages 17·3–28·7 μm long and a basal appendage 4·3–7·5 μm long. Based on morphological characters described above, the fungus was identified as P. guepinii (Sutton, 1980).
A pathogenicity test was performed in July 2009 on current year shoots of P. lentiscus var. chia. The shoots were wounded with a 5-mm punch. Mycelial plugs 5 mm in diameter from a 21 day old culture (PDA) were placed on the wounds and covered with Parafilm and aluminium foil. After 27 days, control wounds inoculated with sterile PDA plugs had healed, but the P. guepinii- inoculated wounds showed lesions in the bark and wood discoloration. The pathogen was successfully re-isolated from the infected shoots, confirming Koch’s postulates. This fungus has been reported to cause twig blight on hazelnut and walnut in Turkey (Karaca & Erper, 2001), but this is the first record of P. guepinii on P. lentiscus var. chia.