Calosphaeria canker of sweet cherry in Trentino (north-eastern Italy)

Abstract: In the recent years branch and trunk dieback of sweet cherry (Prunus avium L.) trees has been observed in Trentino (north-eastern Italy). Plants were stunted with wilted shoots and branches, internal canker and wood necrosis. The development of black perithecia was observed beneath the bark, in correspondence with the canker. Isolation from symptomatic branches was carried out by plating fragments of diseased wood tissues on culture media. Fungal colonies were transferred and identified with morphological and molecular methods, as well as with morphological observations of perithecia. Isolation from symptomatic branches consistently yielded pink-red colonies. Based on the observed characteristics of both perithecia and conidia, the fungus was identified as Calosphaeria pulchella (Pers.) J. Schröt. Identification was confirmed by BLAST analysis based on 100% ITS sequence similarity with GenBank references. The pathogenicity of C. pulchella isolates was evaluated by inoculating the trunk and shoots of two-year-old potted sweet cherry plants. Isolation from discoloured tissues was carried out. Twenty-one months after inoculation, some shoots started to show stunted growth and withering. C. pulchella was re-isolated from inoculated shoots and trunks.