Brown rot caused by Monilinia fructicola is one of the most important diseases of peach. The pathogen is included in the EPPO A2 list of quarantine organisms for Europe (2). M. laxa and M. fructigena are common in Hungary, but M. fructicola has never been reported in orchards, in trade, or in markets. In early October 2005, brown rot was observed on imported peaches from Italy and Spain at a vegetable market and some supermarkets in Budapest. The variety of peach was identified as ‘Michellini’ by colleagues in the Department of Pomology of Corvinus University. The pathogen was identified as M. fructicola on the basis of morphological and molecular characteristics. Symptoms began with a small, circular brown spot, and the rot spread rapidly. At the same time, numerous small, grayish stromata developed. Finally, the whole surface of the fruit was covered with conidial tufts. The conidia were one-celled, lemon-shaped, hyaline, 15.7 × 10.3 μm, and produced in branched monilioid chains. Conidia from infected fruit were transferred to potato dextrose agar. Fungal mycelium grew at a linear rate of 10.7 mm per 24 h at 22°C in the dark. The color of the colony was grayish, and the sporulation showing concentric rings was abundant (sporulation is sparse in M. laxa or M. fructigena). The colony was not rosetted and the margin was not lobed, in contrast with M. laxa. Pathogenicity was tested by inoculating surface-sterilized, mature peach fruits with conidia. Inoculated and control fruits were placed in a sterilized glass container at room temperature. After 5 days of incubation, typical brown rot symptoms developed on inoculated fruits while control fruits remained healthy. M. fructicola was reisolated from the inoculated fruits. PCR was used to identify the fungus (1). Species-specific internal transcribed spacer (ITS) primers for M. fructicola, M. laxa, and M. fructigena were used to amplify the DNA of isolates. Three type-cultures were used as the positive control. Following the removal of the mycelia from the agar, total DNA was extracted using a cetyltrimethylammoniumbromide extraction. The nucleic acid-containing pellet was resuspended in RNase containing Tris-EDTA buffer. DNA quality was assessed by gel electrophoresis on 1% agarose gel stained with ethidium bromide. The molecular genetic identification method confirmed the results of morphological identification. To our knowledge, this is the first report of M. fructicola on peaches in Hungary or in eastern Europe.
References: (1) R. Ioos and P. Frey. Eur. J. Plant Pathol. 106:373, 2000. (2) OEPP/EPPO. List of A2pests regulated as quarantine pests in the EPPO region. Version 2005-09. Online publication, 2005.
