First Report of Trichothecium roseum Causing Pink Fruit Rot of Prunus davidiana in China

Abstract

Pink fruit rot of peach (Prunus davidiana) was observed in an orchard near Huairou, Beijing, China, in 2018. Approximately 90% of peach trees were infected, and diseased fruits were covered with pink-colored mold. To identify the causal agent, diseased fruits were collected, and fungal isolates were obtained from symptomatic fruit tissue. Initially, on potato dextrose agar, the isolates produced thin mycelium, with rare aerial hyphae at 28°C. After 3 days of incubation, the mycelium became pink and produced numerous powdery conidia. Conidia were pyriform, ovate, with papillary protuberances at one end. They were colorless individually but pinkish in mass, with one septation that slightly constricted the middle of the spore. The conidia had an average size of 15 × 6 μm under a light microscope. Two isolates, HB1-1a and HB1-2c, were used in the pathogenicity tests. Each isolate was inoculated onto 10 healthy P. davidiana fruit by pipetting with 100 μl of spore suspension at the concentration of 1 × 10⁶ conidia/ml. Distilled water served as the control. All treated fruits were enclosed in a plastic bag and stored at 28°C under a 12-h light/dark cycle. After 15 days of incubation, symptoms similar to those observed in the orchard developed. The same fungus was reisolated from the diseased fruit. To further confirm the identity of the pathogen, the internal transcribed spacer (ITS) and part of the 5′ end of the β-tubulin (TUB) genes of the isolates HB1-1a and HB1-2c were amplified by using two different primer sets: ITS1/ITS4 (White et al. 1990) and T1/T22 (Hamid et al. 2014). The PCR products had sizes of approximately 700 bp for ITS and 1.5 kb for TUB. The ITS sequence of isolates HB1-1a and HB1-2c (GenBank nos. MN629234 and MN629235) indicated 99.67% identity with Trichothecium roseum (GenBank no. EU552162.1). The partial β-tubulin gene sequence (GenBank nos. MN640076 and MN640077) showed a 100% homology with T. roseum strain UoS09 (GenBank no. KJ607590.1). Therefore, this fungus was identified as T. roseum based on morphological characteristics and molecular data. T. roseum is reported to have a wide range of host (Hong et al. 1997; Inacio et al. 2011). In China, this fungus was first to be found in apple fruit introduced by a traveler in 2018 (Xu et al. 2018). To our knowledge, this is the first report of T. roseum causing pink fruit rot of P. davidiana in China.