First record of leaf spots and stem lesions on Pistacia lentiscus caused by Cylindrocladium pauciramosum and C. scoparium in Italy

Abstract

In November 2005, a foliage disease of mastic tree (Pistacia lentiscus, Anacardiaceae) was noticed in one nursery located in Giarre (Catania) in eastern Sicily (southern Italy). Symptoms including leaf spots, stem lesions, and severe defoliation were observed on about 25% of the young (10–12 months old) and pot-growing seedlings. In high moisture conditions, leaf tissues were covered with a fluffy white mass of fungal mycelium and abundant conidia referable to the genus Cylindrocladium. Hyphal tips were transferred to potato dextrose agar and typical microsclerotia formed after two weeks. The identification of the pathogens was performed on eight fungal colonies grown on carnation leaf agar (CLA) on the basis of their respectively obpyriform or pyriform to broadly ellipsoidal terminal vesicles, conidiophore branching pattern, and conidium morphology. Five of these colonies were identified as C. pauciramosum and the remaining three as C. scoparium (Polizzi & Crous, 1999; Crous 2002). In addition, their ability to mate with Italian and South African tester strains of selected C. pauciramosum and C. scoparium isolates, as well as perithecial morphology, confirmed the identification of fungal colonies. Pathogenicity tests were done by inoculating 1-year-old mastic tree seedlings with the conidial suspensions (1 × 105 CFU per mL) obtained from 14-day-old single-spore colonies of C. pauciramosum grown on CLA at 25°C. Control plants were sprayed with sterile distilled water. All plants were maintained in polyethylene bags in which the temperature was 25 ± 1°C and relative humidity was 95 to 100%. After a week, all inoculated plants developed severe symptoms similar to those observed originally in the nurseries. Cylindrocladium pauciramosum was always re-isolated from infected tissues thus fulfilling Koch's postulates. No symptoms were detected on the control plants. Cylindrocladium scoparium was recently reported affecting mastic tree seedlings in the same area where it was responsible for leaf spots, stem lesions, blight, and crown rot (Polizzi et al., 2006) but this is the first record of leaf spots, stem lesions, and defoliation of P. lentiscus caused by C. pauciramosum and it also represents the first report of coexisting infections due to both species.