Arthrinium arundinis, a Novel Causal Agent of Moso Bamboo (Phyllostachys edulis) Culm Rhomboid Rot and Its Sensitivity to Fungicides

Abstract

Culm rhomboid rot is a new disease of Moso bamboo (Phyllostachys edulis) and mainly occurs on Moso bamboo grown at an altitude above 800 m. The typical symptoms start with black spots and irregular shapes, which expand vertically into an elongated, fusiform, or rhomboid shape up to 15 cm in length. Eleven fungal isolates were isolated from infected tissue, and the isolate BBB1 was confirmed as the pathogen following Koch’s postulates in vitro and in vivo. Regarding morphology, BBB1 was identified as Arthrinium sp.–conidia single-celled, brown to dark, smooth, globose to subglobose, with an equatorial slit, 5.0–9.3 × 3.1–7.3 μm in size. The conidiophores were reduced to conidiogenous cells, pale brown to dark, smooth, and ampulliform. Phylogenetic analysis based on ITS-TEF1-α-TUB2 concatenate sequences identified BBB1 as A. arundinis. Furthermore, the sensitivity of the pathogen against six common fungicides was investigated with mycelial growth assays. Prochloraz exhibited the most potent inhibition with an EC50 value of 0.019 mg/L; another effective fungicide was difenoconazole, with an EC50 value of 0.195 mg/L. This is the first report of A. arundinis causing culm rhomboid rot of Moso bamboo in China; the results provide a basis for managing Moso bamboo culm rhomboid rot.