Screening Of Medicaments For Prevention And Treatment Of Phoma Segeticola Var. Camelliae And Study Of Their Mechanism Of Action

Phoma segeticola var.camelliae was isolated from tea leaf spot disease by our research group in tea garden,Shiqian county,Guizhou province.Tea leaf spot disease presented in tender leaves,fresh shoots and mature leaves.The infected leaves were deformed,distorted and easily deciduous.And the growth and development of infected leaves is slow,which affected seriously.the quality and yield of tea At present,there are no effective measures of prevention and control.In this study,the method of mycelial growth rate was used to determine the antifungal activity of Zhongshengmycin,Kasugamycin and Ningnanmycin against P.segeticola var.camelliae strain GZSQ-4.The results showed that EC₅₀ values are 5.10μg/mL,140.17μg/mL and 2553.85μg/mL,respectively.The antifungal mechanism of Ningnanmycin has not been reported,which is worth to further study.In order to further study the mechanism of Ningnanmycin on GZSQ-4,the mycelium treated with the EC₅₀ Ningnanmycin for 1 h and 14 h was observed by optical microscope,scanning electron microscopy and transmission electron microscopy,respectively.It was found that the mycelium swelled,the mycelial cytoplasmic density decreased,the granular content appeared and the number of mitochondria granules increased.The nucleus of mycelium treated with Ningnanmycin had no significant changes after stained with DAPI.The effect on gene expression of GZSQ-4 was studied by RNA-seq.The results showed that 1363 differentially expressed genes（DEGs）were identified with 743 genes up-regulated and 620 genes down-regulated of GZSQ-4,which treated by Ningnanmycin at the concentration of EC₅₀ for 1 h.By GO enrichment analysis,the differentially expressed genes were most enriched in the structural constituent of ribosome of molecular function,ribosome of cellular component and the translation of biological process.10 DEGs selected randomly from Ningnanmycin 1 h treatment group were verified by RT-qPCR.The results shows that the expression level of DEGs is consistent with the result transcriptome sequencing.Preliminary results indicate that Ningnanmycin mainly affects ribosome composition of GZSQ-4 and the related processes of translation.