A Chitosan Composite Film Sprayed before Pathogen Infection Effectively Controls Postharvest Soft Rot in Kiwifruit

Soft rot caused by Botryosphaeria dothidea and Phomopsis sp. is a critical disease in kiwifruit. In order to efficiently control soft rot, a 28.6% chitosan composite film (CCF) containing chitosan, dextrin, ferulic acid, calcium, and auxiliaries was successfully developed. The results showed that CCF had a strong inhibitory effect on mycelia growth of B. dothidea and Phomopsis sp., with mycelial EC50 values of 68.11 and 50.34 mg L−1, respectively. The concentration of 0.71–1.42 g L−1 CCF had noticeably preventive and curative effects against soft rot. The spray of CCF before pathogen infection effectively reduced the incidence of soft rot, remarkably increased the content of resistance compounds, and activated the activity of defense enzymes. Moreover, it notably enhanced the yield and quality and prolonged the shelf life of kiwifruit. Therefore, the excellent control effects of CCF against soft rot might be associated with its film-forming property and antifungal activity, which prevent infection and induce plant defense mechanisms. The concentration of 0.71–1.42 g L−1 CCF was optimal for the field application before the onset of disease symptoms in plants with B. dothidea and Phomopsis sp.