Identification and Biological Characteristics of Alternaria gossypina as a Promising Biocontrol Agent for the Control of Mikania micrantha

Mikania micrantha is one of the most threatening invasive plant species in the world. Its invasion has greatly reduced the species diversity of the invaded areas. The development of fungal herbicides using phytopathogenic fungi has attracted considerable attention in recent years. In this study, a tissue isolation method was used to isolate and screen the strain SWFU-MM002 with strong pathogenicity to M. micrantha leaves from naturally occurring M. micrantha. Through morphological observation, ITS, GAPDH, and Alta-1 gene sequence homology, we compare and construct a phylogenetic tree to determine their taxonomic status. In addition, the biological characteristics of strain SWFU-MM002 were studied. The results showed that, combined with morphological and molecular biology identification, the strain was identified as Alternaria gossypina; biological characteristic research showed that the optimal medium for the growth of mycelium of this strain is PDA medium. At the optimal temperature of 27 °C and pH between 6 and 10, the mycelium can grow well. The best carbon and nitrogen sources are maltose and peptone, respectively. Analysing the infection process under a light microscope showed that SWFU-MM002 mycelia invaded the leaf tissue through stomata and colonized, eventually causing damage to the host. This is the first report of leaf spot of M. micrantha caused by A. gossypina. This study can lay a solid foundation for the development of A. gossypina as a control agent for M. micrantha.