First Report of Brown Rot Caused by Monilia mumecola on Chaenomeles lagenaria in China

Abstract

Chaenomeles lagenaria (Loisel) koidz (Rosaceae) is a traditional medicinal plant widespread in China known for its antitumor, heart-strengthening, and antiphlogistic properties (Zhang et al. 2014). Recently, symptoms of brown rot on C. lagenaria have been observed causing 60% yield losses in Changyang county, Hubei province, China. The pathogen mainly infected flowers and fruits. Infected flowers exhibited symptoms of small auburn spots on the tip of bracts and sepals at the beginning, developing along the main vein toward the base of the flowers, resulting in the decay of pedicel. Infected fruits developed round, dark-brown spots with tawny liquid on the surface and progressively rotted and withered. As the disease progressed, a white mycelium occurred on infected tissue in the presence of increased humidity. Symptomatic fruits and flowers were cut into small pieces and disinfected with 1% NaOCl solution for 1 min, rinsed in sterile water, air dried, and placed on potato dextrose agar (PDA). Pure cultures were obtained by using the single-spore isolation method and incubating at 25°C in light. The radial mycelial growth was 7.5 mm/day; compact colony with wavy edges was formed on PDA after 12 days of growth on a 9-cm Petri dish. The mycelium was colorless at first and turned incanus with time. Hyphae were septate and branched. Strings of spherical, colorless conidia with a size of 4 to 22 × 6 to 10 μm developed on short conidiophores. Based on morphological characteristics of mycelia and conidia, isolates were identified as Monilia mumecola (Wei 1979). The internal transcribed spacer (ITS) region of rDNA was amplified using ITS1 and ITS4 primers and sequenced. BLAST analysis of the PCR product showed 99% identity to M. mumecola (AB125620, AB125613). The sequence of isolate was shown in the supplementary file. To verify the pathogenicity, fresh disinfected fruits of C. lagenaria were used for the inoculation test. A group of 10 healthy fruits were inoculated with mycelium plugs; meanwhile, another group of 10 fruits were inoculated with conidial suspension at a concentration of 1 × 10⁶ per milliliter. Ten more noninoculated fruits served as controls. All inoculated and noninoculated fruits were placed in a light cultivation room at 25°C with saturated humidity. Five days later, inoculated fruits in both groups began to brown. By 10 days after inoculation, 100% of the inoculated fruits showed symptoms identical to those observed in the orchard. Control fruits remained symptomless. M. mumecola was reisolated from the inoculated fruits. The experiment was repeated twice. M. mumecola has only been reported to cause brown rot on Prunus mume in Japan (Harada et al. 2004) and peach in China (Hu et al. 2011). To our knowledge, this is the first report of brown rot caused by M. mumecola on C. lagenaria in China.