Low-temperature atmospheric pressure plasma as a new control method against Botrytis cinerea

Grey mould caused by B. cinerea can seriously affect numerous products, both in the field and postharvest. Disease management is usually achieved by fungicides, but the implementation of more sustainable and innovative technologies is increasingly required. Low temperature plasma (LTP) represents a novel promising tool against fungal contamination of products. LTP produces an environment rich in charged particles, reactive oxygen and nitrogen species (RONS), and ultraviolet radiation. LTP can be applied either directly or indirectly by enriching a medium, such as nebulized water (plasma activated fog PAF), with long-lived RONS. The effects of direct applications of LTP treatments on conidia germination of B. cinerea was evaluated using three different Dielectric Barrier Discharge configurations: surface (SDBD), volume (VDBD) and plasma-jet (APPJ). A significant reduction in the percentage of germinated conidia on water-agar medium was recorded after exposures of 1 min or 5 min to SDBD or APPJ, while a complete inhibition was reached after 3 or 10 min of exposure, and 30 sec for VDBD treatment. UV-induced albino B. cinerea mutants, with cream-coloured conidia, showed higher sensitivity to plasma treatments compared to the wild-type strain suggesting that melanin and other pigments could affect fungal response to plasma exposure. The efficacy of PAF was assessed on both conidia germination and fruits of strawberry and table grape exposed to different times of plasma treatment. PAF presented a high efficacy, with complete inhibition of conidia germination achieved after 3-5 min of exposure. Significant reductions in the disease symptoms (≥ 70%) leading to a shelf-life extension of treated fruits, following 5-min exposure, were recorded. Moreover, the activation of defence responses in strawberry fruits exposed to the treatments was revealed by whole transcriptome analysis suggesting their possible role in early resistance to infections.