Fusarium dry rot on potato, caused by the fungal pathogen Fusarium solani is characterized by an internal light to dark brown or black and usually dry rot of the potato tubers. The disease progresses noticeably faster during the last half of the storage season. Biological control of dry rot is an intriguing concept, but currently nothing is available commercially. It was found that the essential oil of a number Lamiaceae species, including oregano, have strong biocidal properties. Significant antifungal activity of Origanum vulgare ssp. hirtum essential oil against different phytopatogens in in vitro experiments has been demonstrated. In the present study effect of oregano essential oil on potato tuber infected with Fusarium solani was evaluated. For this purpose potato slices with cut thickness 8-10 mm were inoculated with mycelium plugs of F. solani in the slice center. The oregano oil was tested in two approaches - contact and airimpact. In the first approach, the essential oil was applied as an aqueous solution with concentration range of 1-3 µg/mL on the potato tubers’ slices. In the second approach, the essential oil was placed in the Petri dishes with tubers’ slices in amounts from 5 to 50 µL without contact between them. A strong reduction in micellar growth on tuber tissue was observed at airimpact application of the essential oil in amounts upper 25 µL. The result showed that the Origanum vulgare ssp. hirtum essential oil shows antifungal activity against Fusarium solani and has the potential for application in the storage rooms of potato tubers especially during the last half of the storage season.

Acknowledgements: This research was supported by the Bulgarian National Science Fund, Bulgarian Ministry of Education and Science (Grant DN 16/2, 11.12.2017).