Cold plasma as a novel treatment to reduce the in vitro growth and germination of Colletotrichum species

This study investigated the use of cold plasma to reduce the in vitro growth of two postharvest fungal plant pathogens, Colletotrichum alienum and C. fioriniae, isolated from avocados. Cold plasma (CP) was used to treat pure cultures and conidial suspensions of both pathogens, for 180 or 360 s, in either open or sealed environments from varying distances. In an open environment, the 360 s treatment at a distance of 5 cm reduced the colony growth of freshly inoculated cultures to less than 2 mm/day compared to the control of more than 8 mm/day, and treatment of conidial suspensions resulted in almost 100% reduction of conidial germination. In the same environment, the 180 s CP treatment did not significantly reduce the colony growth of fresh or actively growing cultures, but did suppress the germination of conidia by up to 80%. In a sealed environment, the 360 s CP treatment also effectively reduced the growth of freshly inoculated cultures, with no growth for some isolates. Production of reactive oxygen and nitrogen species was observed during treatment, and these may have contributed to the reduction in growth and germination. These results demonstrate the potential of CP for the control of two Colletotrichum species.