Isolation And Identification Of The Causal Pathogens For Kiwifruit Bacterial Canker And The Antagonistic Endophytic Fungi From Kiwifruit In Sichuan, China

Sichuan Province is one of the major kiwifruit producing areas in China. However, the main kiwifruit variety "HongYang" kiwifruit got infected by kiwifruit bacterial canker with great economic loss. Kiwifruit bacterial canker is a devastating bacterial disease and difficult to control. Numerous studies showed that endophytic fungi colonize in plant tissues. Some endophytic fungi strains exhibit good antagonistic activities. Some endophytic fungi strains are widely used as biological control agents, bacteria fixing and plant growth-promoting agents in laboratory, greenhouse and field therefore they often regarded as the potential source bacterial strains in plant disease bio-control areas. The endophytic fungi strains have large application potential in the field of bio-control, medicine and health. There is a kiwifruit plant show good resistance to kiwifruit bacterial canker in2012, therefore this study isolated and identified the pathogen of kiwifruit bacterial canker in Sichuan "HongYang" kiwifruit variety; isolated and identified the endophytic fungi in this special health kiwifruit plant, analyze the diversity of the endophytic fungi in kiwifruit plant, in order to find a potential antagonistic activity strains to the kiwifruit bacterial canker. The main results were as follow:1The isolation and identification of the kiwifruit bacterial canker pathogen:the pathogen was isolated from the reddish exudates of three sites with different altitude and soil environment. Base on biochemical testing, pathogenic testing and phylogenetic analyses, the results shown that Pseudomonas syringae pv. actinidiae is the causal agents of this "Hongyang" kiwifruit bacterial canker disease.2The isolation and identification of the endopytic fungi in kiwifruit bacterial canker:the endophytic fungi were isolated from kiwifruit leaves and branches.14endophytic fungi of kiwifruit leaves were identified, including Penicillium sp. Colletotrichum sp. Phomopsis sp. Alternaria sp. and Nigrospora sp.8endophytic fungi were obtained from branches, such as Alternaria sp. Nigrospora sp. Phomopsis sp.and Sordaria sp.3one of the endophytic fungi Nigrospora sp.(No.J2) from branch showed good antagonistic activities to Pseudomonas syringae pv. actinidiae in vitro with the inhibition zone of15mm, it also show great genetic stability therefore it has the potential of being used as a biological control agent against kiwifruit bacterial canker.4The normal way of bacterial disease pathogen isolation is to isolate from plant tissues which will be affected by the endophytes in plant tissues since some of the endophytes are similar to the pathogen in shape, therefore this affection increases the work load. This research try to isolate the pathogen from the red exudates produced by the infected plant, it will be more convenient and simple.