Ozone as a post-harvest treatment for potatoes
This project evaluated the potential for using ozone gas as post-harvest treatment for control of disease in stored potatoes. Ozone is a short-lived, highly reactive oxidizing agent with demonstrated potential to control disease-causing microorganisms. Preliminary trials showed that the atmospheric concentration of ozone obtained using commercial ozone generation equipment depended on the room size and reactive demands in the treatment area. Ozone applied to freshly harvested seed-grade potatoes up to 0-20 mg O3/kg/hr for 1, 7 or 21 days had little significant effect on the incidence or severity of a range of diseases or tuber colour, but did increase tuber weight loss in a dosage-dependant manner. Continuous ozone application (1.9 mg O3/kg/hr) accentuated weight loss by the stored crop. Application of ozone (10-20 mg O3/kg/hr) and Purogene® (Chlorine dioxide; 200 ppm) for 1 day at the mid-point of the winter storage period had no effect on disease levels, skin colour or weight loss measured at the end of storage. When tubers were inoculated with a range of pathogens (Fusarium sambucinum, F. solani., Phytophthora infestans, Helminthosporium solani), introduced at wound depths appropriate to each disease, disease levels typically increased, however ozone treatment (20 mg O3/kg/hr) did not reduce development of any of these diseases. In the absence of potential interference by the surrounding storage environment, pure cultures of Fusarium spp., P. infestans and sclerotia of Sclerotinia sclerotiorum were exposed to 45 mg O3/plate/hr for 1 or 2 days. The ozone treatments had no effect on sporulation of any of the pathogens and did not reduce mycelial growth of Fusarium spp. Mycelial growth of Phytophthora and sclerotial germination of Sclerotinia were suppressed for the duration of the ozone treatment period, however normal growth resumed when the cultures were placed in ozone-free conditions. Ozone treatments (up to 320 mg O3/kg/hr for 2 days) did not reduce the sprouting ability of seed potatoes, however ozone treatments (~20 mg O3/kg/hr for 1, 7 or 21 days) significantly reduced wound periderm thickness of treated potatoes. Treating seed potatoes with ozone (0 or 20 mg O3/kg/hr for 1 or 2 days) prior to planting typically did not affect plant stand or yield, however under cool, wet conditions, ozone-treated seed potatoes produced poorer stands and yields relative to the controls. Based on the results obtained for the range of treatments evaluated in this project, ozone appears to have limited potential as a disease management tool in stored potatoes.
potato, post-harvest, disease, ozone
Master of Science (M.Sc.)