Identification of Nigrospora oryzae Causing Leaf Spot Disease in Tomato and Screening of Its Potential Antagonistic Bacteria.

Abstract

Tomato is a widely cultivated vegetable crop worldwide. It is susceptible to various phytopathogens, including fungi, bacteria, viruses, and nematodes. In 2024, an unknown leaf spot disease outbreak, characterized by distinct brown necrotic lesions on leaves, was observed in tomato plants in Yunnan Province, China. Through rigorous pathogen isolation and the fulfillment of Koch's postulates, it was proved that the fungal isolate could infect tomato leaves and cause typical symptoms. The pathogen isolated from tomato leaves was identified as Nigrospora oryzae based on its morphology and using a multilocus sequence analysis method with the internal transcribed spacer gene (ITS1), beta-tubulin gene (TUB2), and translation elongation factor 1-alpha gene (TEF1-α). This represents the first documented case of N. oryzae infecting tomatoes in the world. Given the damage caused by N. oryzae to tomato plants, we explored biocontrol methods. Through a dual-culture assay on PDA plates, Bacillus velezensis B31 demonstrated significant biocontrol potential, exhibiting strong antagonistic activity toward N. oryzae. In addition, we developed a polyethylene glycol (PEG)-mediated transformation system that successfully introduced pYF11-GFP into the protoplasts of N. oryzae. This achievement provides a foundation for future genetic manipulation studies of N. oryzae.