Objective To clarify the pathogen causing anthrax disease of passion fruit in Guangxi and its biological characteristics, providing a theoretical basis for its prevention and control.

Method Plant tissue isolation method was used for pathogen isolation, pathogenicity determination, and morphological characteristic observation. Combined with ITS, CAL, and ApMat gene sequence analysis, the pathogen causing anthrax disease of passion fruit in Guangxi was identified, and its biological characteristics were clarified.

Result A representative strain tg3b1 was isolated and purified from the typical symptom of anthrax disease lesion tissue of passion fruit. Through morphological identification, multi-gene sequence analysis and pathogenicity determination, the pathogen of this disease was identified as Colletotrichum theobromicola. The colony diameter and spore production of the pathogen mycelium were the largest at 25-28°C, which were significantly higher than those at other temperature conditions (P＜0.05, the same below). The colony diameter and spore production of the pathogen were the largest at pH 6.0, which were significantly higher than those at other pH conditions. The mycelial growth of the pathogen was not sensitive to light conditions. The spore production was the largest when the light condition was alternate light and dark, which was significantly higher than those at other light conditions. The colony diameter of the mycelium on PSA medium was the largest, which was significantly higher than those on the other 8 media. The spore production was higher on OA and PDA media, which was significantly higher than those on other media. When the carbon source was glucose, the colony diameter was the largest, and the mycelial growth was dense; when the carbon sources were D-fructose and glucose, the spore production was the largest, which was significantly higher than those under other carbon source conditions except lactose. When the nitrogen source was yeast powder, the colony diameter was the largest, which was significantly higher than those under other nitrogen sources; the nitrogen sources with higher spore production were glycine and L-arginine, which were significantly higher than those under other nitrogen sources. The lethal condition of the pathogen mycelium was treatment at 51°C for 10 minutes.

Conclusion Colletotrichum theobromicola is the pathogen causing anthrax disease of passion fruit in Guangxi. The most suitable conditions for the mycelial growth of this pathogen are: temperature of 25-28°C, pH of 6.0, no requirement for light, PSA medium, carbon source of glucose, and nitrogen source of yeast powder. The optimal spore production conditions are: temperature of 25-28°C, pH of 6.0, alternate light and dark for light, PSA medium, carbon sources of D-fructose and glucose, and nitrogen sources of glycine and L-arginine. The lethal condition of this pathogen is treatment at 51°C for 10 minutes.