First Report of Brown Rot of Peach Caused by Monilinia fructicola in Southeastern China.

Abstract

In 2009 and 2010, peaches (Prunus persica) with brown rot symptoms were collected from Zhejiang Plant Protection State Research Farm and a commercial orchard in Fujian Province in southeastern China. Affected fruit showed brown decay with zones of sporulation. Single-spore isolates from the diseased fruit were cultured on potato dextrose agar. After incubation at 25°C in the dark for 5 days, colonies were gray with concentric rings of sporulation. Mean mycelial growth of isolates MZ09-2a from Zhejiang Province and 0907-a from Fujian Province was 4.46 ± 0.58 and 7.05 ± 0.81 cm after 4 and 7 days of incubation, respectively. Lemon-shaped conidia were formed in branched, monilioid chains and mean size was 14.6 (9.6 to 21.6) × 10.3 (7.2 to 13.2) μm. Mean conidial germination was 97 ± 1% with one straight germ tube per conidium. These characteristics were consistent with descriptions of Monilinia fructicola (G. Wint.) Honey (3). Morphology-based species identification was confirmed by sequencing and analysis of ribosomal internal transcribed spacer (ITS) sequences. A 496-bp fragment including ITS 1 and 2 and the gene encoding the 5.8S small subunit of the ribosomal RNA from isolates MZ09-2a and 0907-a was amplified using the universal primer pair ITS1/ITS4 (4) and sequenced. Nucleotide sequences of both isolates were identical. Blast searches of the ITS sequences in GenBank showed the highest similarity (100%) with sequences of M. fructicola isolates from China (FJ515894), Italy (FJ411109), and Spain (EF207423). The isolates were also identified as M. fructicola using the Monilinia spp. PCR detection protocol based on sequence-characterized amplification region marker DNA sequences (2). Pathogenicity was confirmed by inoculating surface-sterilized, mature cv. Zhonghua 2 peaches with mycelial plugs of representative isolates. Fruit was stabbed at two points with a 5-mm-diameter sterile cork borer, mycelial plugs (5 mm in diameter) were removed from the periphery of a 4-day-old colony of each isolate and placed upside down into each wound; control fruit received water agar. Inoculated fruit developed typical brown rot symptoms with sporulating fungi while control fruit remained healthy after 3 days of incubation at 22°C in a moist chamber. Pathogens were reisolated from the inoculated fruit and confirmed to be M. fructicola on the basis of morphological characteristics. To our knowledge, this is the first report of M. fructicola in Zhejiang and Fujian provinces. Both provinces are located more than 1,000 km south of Beijing, Hebei, and Shandong provinces, where M. fructicola had been reported previously (1).