Identification and pathogenicity of Alternaria alternata causing leaf spot disease on sweet cherry in Province of Turkey

Sweet cherry leaf spot, caused by Alternaria spp., causes significant yield losses to sweet cherry production globally. This study was aimed at morphological and molecular identification of the causal agent, Alternaria spp., of leaf spot disease on sweet cherry in the Usak province, Turkey. Isolates were also tested for pathogenicity. In April-June in 2018 and 2019, the sampling was conducted in a total of 84.4 hectares in 70 orchards that were selected to represent the province of Usak where the highest sweet cherry farming takes place. In the first year, the incidence of Alternaria spp. was highest in the Central district (31.8%) while in the second year high incidences were found in Central (50%), Esme (33.3%) and Banaz (26.9%) districts. The isolated Alternaria spp. was identified based on morphological and microscopic characteristics. Pathogenicity tests were conducted for all isolates based on Koch's postulates and were made on cultivar Ziraat 0900 of sweet cherry in the climate chamber conditions. The phylogenetic analysis using sequences of the internal transcribed spacer region of the ribosomal RNA (ITS rRNA), translation elongation factor (TEF) and RNA polymerase II subunit (RPB2) genes showed that our isolates clustered in the same branch with reference isolates of A. alternata. This study is the first report of A. alternata causing of leaf spot disease of sweet cherry in Turkey.