The Preliminary Research On Mechanism Of Tea Plant-colletotrichum Interaction

Tea plant（Camellia sinensis）is one of the most important cash crops.In the fields,the growth of tea leaves and shoots might be influenced by abiotic and biotic stresses,sequentially reducing yields.Colletotrichum is a primary fungal pathogen with wide distribution and multiple hosts including tea plant.The tea plant-colletotrichum interaction research will improve understanding of tea plant’s response mechanism to biotic stress especially for its disease-resistant mechanism.In this study,we researched into the biological characteristics and pathogenicity of main Colletotrichum species in tea plant.Furthermore,using the inoculation and omics analyses probed into the transcriptional and metabolic changes in the interaction of tea plant against Colletotrichum.The major findings are as follows:（1）Clarifying dominant species of Colletotrichum in tea plant and comparing their differences in biological characteristics and pathogenicity.A combination of multigene（ITS,ACT,GAPDH,TUB2,CAL,and GS）and morphology analyses showed that the 38 strains isolated from tea leaves belonged to two different species,namely,Colletotrichum camelliae and C.fructicola.These two species have significant morphological differences.On PDA culture medium,mycelia of C.camelliae were denser than C.fructicola.Isolates of C.fructicola were more capable of producing spores than C.camelliae isolates.C.camelliae was more sensitive to environmental changes than C.fructicola.Pathogenicity tests revealed that C.camelliae was more invasive than C.fructicola.Under caffeine and low concentration of catechins treatments,the growth inhibition rates of C.fructicola were remarkably higher than C.camelliae.When concentration of catechins was above 1 mg·m L^-1,the growth inhibition rates of C.camelliae increased.（2）Inoculating tea plant with virulent strain order to illustrate the process of interaction.In the case of wound inoculation,germ tubes just generated after 12 h,appressoria formatted at 24 h,acervuli developed at 72 h when scabs were observed.In the case of non-wound inoculation,germ tubes and appressoria developed at 12 h and 24 h,respectively.But no scabs appeared with time going on.（3）Based on transcriptom and metabolome analysis,we found the main response in three stages.A total of 10592 differentially expressed genes（DEGs）were identified from the transcriptomic data of tea plants and were significantly enriched in callose deposition and the biosynthesis of ethylene（ET）processes.Subesequently,3555 mass spectra peaks were obtained by LC-MS detection in negative ion and 27,19 and 81 DEMs at 12 h,24 h and 72 h,respectively.Metabolomic analysis also revealed that the levels of precursors and intermediate products of jasmonic acid（JA）biosynthesis significantly increased during the interaction,especially when symptom became apparent.In conclusion,we suggest that callose deposition and JA/ET signaling system play important roles in the tea plant-C.camelliae interaction.（4）In order to verify the transcriptomic and metabolomic founds and clarify the roles of phytohormones,we detected the contents of salicylic acid（SA）and JA.Results showed that the content of SA reduced in the infected leaves and the content of JA sharply increased in the period of disease.