The Identification and Role of the Key Mycotoxin of Pestalotiopsis kenyana Causing Leaf Spot Disease of Zanthoxylum schinifolium

Abstract

Leaf spot is a common disease of Zanthoxylum schinifolium (Z. schinifolium), which can seriously harm the plant’s ability to grow, flower, and fruit. Therefore, it is important to identify the mechanism of leaf spot caused by Pestalotiopsis kenyana (P. kenyana) for thorough comprehension and disease control. In this study, to verify whether the mycotoxins produced by P. kenyana cause leaf spot disease, the best medium for P. kenyana, namely PDB, was used. The mycotoxins were determined by ammonium sulfate precipitation as non-protein substances. The crude mycotoxin of P. kenyana was prepared, and the optimal eluent was eluted with petroleum either/ethyle acetate (3:1, v/v) and purified by silica gel column chromatography and preparative high-performance liquid chromatography to obtain the pure mycotoxins PK-1, PK-2, and PK-3. The PK-3 had the highest toxicity to Z. schinifolium, which may be the primary mycotoxin, according to the biological activity test using the spray method. The physiological and biochemical indexes of Z. schinifolium plants treated with PK-3 mycotoxin were determined. Within 35 days after mycotoxin treatment, the results showed that the protein content and malondialdehyde content of leaves increased over time. The soluble sugar and chlorophyll content decreased over time. The superoxide dismutase activity and catalase activity of the leaves increased first and then decreased, and the above changes were the same as those of Z. schinifolium inoculated with the spore suspension of the pathogen. Therefore, it is believed that the mycotoxin pestalopyrone could be a virulence factor that helps P. kenyana induce the infection of Z. schinifolium. In this study, the pathogenic mechanism of Z. schinifolium leaf spot was discussed, offering a theoretical foundation for improved disease prevention and control.