Isolation, Identification and Biological Characteristics of Pathogenic Fungi from Kiwifruit and Pakchoi

Objective: Kiwifruit (Actinidia chinensis Planch.) and pakchoi (Brassica rapa var. chinensis) are easy to rot due to pathogens during storage and transportation, resulting in economic losses. Therefore, it is necessary to understand the species and characteristics of pathogenic bacteria for prevention and control of pathogenic bacteria. Methods: In this study, pathogenic fungus were isolated from infected kiwifruit and pakchoi, and identified by pathogenicity identification, morphology identification, and Internal Transcribed Spacer identification. The biological characterization of these pathogenic fungus were also investigated. Results: Four pathogenic fungi were isolated and purified from infected kiwifruit, and identified as Cytospora sp., Penicillium polonicum, Botrytis californica, Trichoderma gamsii, respectively. Three pathogenic fungi were isolated and purified from infected pakchoi, and identified as Fusarium circinatum, Cladosporium angustiterminale, Botrytis californica, respectively. Cytospora sp. could grow in the range of 10~28 ℃. The other 6 pathogenic fungi could grow in the range of 4~30 ℃, and the optimum growth temperature of these pathogenic fungi was 20~28 ℃. Except for Cladosporium angustiterminale, the optimum pH value of the other six pathogenic fungi was between 6 and 8. Cladosporium angustiterminale was more resistant to acid, and its optimum pH value might be below 4. Cytospora sp. could grow in the pH range of 4~9, and the other 6 strains could grow in the pH range of 4~10. Conclusion: After pathogenicity identification, it was found that these seven strains could cause the decay of kiwifruit and pakchoi, and Botrytis californica could cause the decay of kiwifruit and pakchoi at the same time. Penicillium polonicum, Botrytis californica, Trichoderma gamsii and Cladosporium angustiterminale could all grow at 4 ℃, indicating that the temperature of refrigeration could not prevent these pathogens from infusing fruits and vegetables. This study provided a reference basis for the control of pathogenic fungi in kiwifruit and green vegetables.