Impact of ozonized water on Botrytis cinerea conidia: physiological state, ultrastructure and incidence in strawberry fruit

ROMERO-BERNAL, ANGELA; CONTIGIANI, EUNICE; GONZALEZ, HÉCTOR L.; ALZAMORA, STELLA M.; RAFFELLINI, SILVIA; GÓMEZ, PAULA

Texas

Congreso; Institute of Food Technologist Annual Meeting (IFT 2021); 2021

Institute of Food Technologist

Botrytis cinerea causes gray mold diseases in many important crops. Ozone is an ecofriendly alternative to synthetic fungicides for controlling postharvest fruit decay. In this study, the impact of ozonized water on the physiological state and the ultrastructure of B. cinerea was investigated in vitro by flow cytometry analysis (FCM) and transmission electron microscopy (TEM). Fungus incidence in artificially contaminated strawberries during refrigerated storage was also evaluated.B. cinerea BAFC 3003 (105 conidia/mL, 0,5 L) were exposed to ozonized water (2.5  0.4 and 4.50.2 mg O3 / L) in a bubble column at 20 ± 1 °C, during 0 (control) - 14 min. Viable cells were determined by surface plate count. For FCM, cells were labeled with fluorescein diacetate (FDA) for detecting esterase activity and with propidium iodide (PI) for monitoring membrane integrity. Samples for TEM observations were prepared according to conventional techniques. For in vivo studies, inoculated strawberries (Fortuna cv.) were 5 min-treated with 4.50.2 mg O3 / L and stored 10 days at 6  1 C: Fungus development was daily evaluated by visual inspection.Ozone treatments reduced viable counts by 5 log after 6 - 10 min. Within 1 min-4.5 mg O3/L exposure, subpopulation of slightly permeabilized cells with esterase activity increased to 49 %, whereas the percentage of intact cells decreased to 25 %. After 4 min, both subpopulations decreased to ≤ 1 % and the percentage of cells without esterase activity and compromised membranes increased to ≈ 73 %. Further treatment times increased the subpopulation of unstained cells/cell fragments to 58 %. Accordingly, ultrastructure images showed cells with markedly undulated walls and retraction and disruption of cytoplasm with absence of plasmalemma, empty cells and numerous cells debris. Similar trends were shown at the lowest ozone level. A 5 day ?delay on the onset of infection and a lower fungus incidence during storage in treated fruit compared to control was observed. Ozone induced irreversible changes in membranes permeability, cell lyses and rupture and esterase inactivation in B. cinerea and could be a strategy in combination with other stressors to control this fungus in the post-harvest.