First report of brown rot on peach, nectarine, cherry, and plum fruits caused by Monilinia fructicola in Bulgaria.
Field surveys in the region of Plovdiv (Bulgaria) within a small mixed orchard of peach and nectarine trees in the summer of 2017 revealed symptoms and signs of brown rot attended by numerous, slightly greyish conidial pustules on the surface of unripe and mature fruits. Similar symptoms and signs were found also in the summer of 2018 on cherry and plum fruits in two additional orchards in the same region. The putative Monilinia species was isolated by transferring conidia from naturally infected fruits of these four Prunus species to potato dextrose agar (PDA). After 24 to 48 h of incubation at 25°C, germinated conidia were transferred to PDA, and a week later, greyish-beige colonies with consecutively forming concentric rings of sporodochia appeared. Based on the results of morphological observations, pathogenicity tests and DNA sequence analysis, it can be concluded that M. fructicola is the causal agent of the observed brown rot on peach, nectarine, cherry and plum fruits. This is thought to be the first report of M. fructicola in Bulgaria.