Comparison And Preliminary Study On The Mechanism Of Virulence Difference Of Colletotrichum Gloeosporioides Strains Isolated From Litchi

Anthracnose is an important pathogenic fungus with a wide range of hosts,especially,which happened in tropical and subtropical regions,and can damage a variety of crops,trees,cash crops and vegetables to modern agricultural production caused serious economic losses.The virluence of11isolates of Colletotrichum gloeosporioides obtained from different areas were investigated by applying detached leaf and fruit inoculation, then we study the biological characteristics of difference of high virluence and low virluence strains.The results showed that there was a significant difference in virluence of all isolates. The virluence of0977-19-2isolate is the strongest, and the opposite is09619-1-1. The results also indicated that both isolates were similar in Colony characteristics. However,0977-19-2had a higher Spores yield and Spore germination rate.They were different in characteristics of conidia and acervulus. These differences may be the important reason of different virluence.The change of some secondary metabolites and several enzymes activities in litchi fruit were determined after inoculating litchi fruit with different isolates.Then we compare physiological response of each other.we can find that polyphenols and anthocyanin content were decreased; malondialdehyde (MDA) content increased; Superoxide dismutase (SOD) activity reduced; the activities of Peroxidase (POD)、 polyphenol oxidase (PPO)、phenylalnine ammonialyase(PAL) and some related enzymes of cytoderm metabolism were increased.But the high virluence strain had a more significant tendency of peel. Physiological response and virluence of different isolates had positive correlation.Different physiological response may be a important reason for different virluence.Compare the infection processs of different virluence strains by skin paraffin.It showed that both isolates has similar in the primary hypha development, colonization, Secondary hyphae, cytolysis,much mycelium, Conidium generation. However,0977-19-2had a higher infection rate,hyphae penetrability, spore production, disease spot,fester. And large formation of acervulus and spores,the latter can only be observed a few spores. The different characteristics of infection and virluence difference have great correlation. Different virluence is the main reason for the different infection process.