The protective effect of bacteriophage suspensions (Ds3CZ + Ds20CZ and PcCB7V + PcCB251) on phytopathogenic bacteria causing soft rot of potato tubers, namely Dickeya dianthicola (D50, D200) and Pectobacterium carotovorum (P87, P224), was observed in ex vivo and in vitro experiments. Ex vivo tests were performed (with air access) on potato slices, on cylindrical cuts from the center of the tubers, and directly in whole potato tubers. In vitro experiments were carried out in a liquid medium using RTS-8 bioreactors, where bacterial growth was monitored as optical density. In particular, the inhibitory effects of phages were confirmed in experiments on potato slices, where suppression of rot development was evident at first glance. Phage treatment against selected bacteria positively affected potato hardness. Hardness of samples treated with bacteria only was statistically significantly reduced (p < 0.05 for D50 and p < 0.001 for D200 and P87). Ex vivo experiments confirmed significant inhibition of P87 symptom development, partial inhibition of D200 and D50 in phage-treated tubers, and no effect was observed for P224. The inhibitory effect of phages against bacteria was not observed in the in vitro experiment.

Pectinolytic bacteria of the family Enterobacteriaceae, specifically Dickeya solani, are known to cause potato blackleg. This study aimed to evaluate the effectiveness of a mixture of two bacteriophages from the genus Limestonevirus in controlling Dickeya solani in both greenhouse and field trials. The potential of bacteriophages for ecological potato control was also assessed. The phages φDs3CZ and φDs20CZ were isolated from soil in the Czech Republic between 2019 and 2021. They were applied preventively and curatively as a solution on artificially wounded and inoculated seed tubers immediately prior to planting. The phage-treated variant showed a highly significant reduction in the extent of D. solani infection compared to the untreated control in both the greenhouse and field trial. The effect of the phages depended on the concentration of the solution, the rate of tuber injury, and the sequence of application. When applied preventively, the phages caused a significantly higher reduction in the rate of blackleg symptoms (86.7% and/or 87.1%) compared to the curative application (54.6 and/or 36.6%). Phages φDs3CZ and φDs20CZ showed potential for use in biological potato control against Dickeya solani.

The pectinolytic Dickeya solani bacterium is an important pathogen found in potatoes. We conducted laboratory and field experiments mimicking severe and mild Dickeya spp. infection and investigated the application of a mixture of two lytic bacteriophages before and after bacterial infection to protect the plants. Application of the phage solution to tuber disks and wounded tubers did not completely eliminate the infection but reduced the development of soft rot symptoms by 59.5–91.4%, depending on the phage concentration. In the field trial, plants treated with bacteriophages after severe Dickeya infection had 5–33% greater leaf cover and 4–16% greater tuber yield compared to untreated plants. When simulating a mild infection, leaf cover was 11–42% greater, and tuber yield was 25–31% greater compared to untreated plants. We conclude that the phage mixture has the potential to protect potatoes ecologically from D. solani.

Potato silver scurf, caused by the fungus Helminthosporium solani, is an important storage disease of potato (Solanum tuberosum L.), reducing the market value of tubers. Using in vitro and in vivo assays, the presented experiments aimed to determine the effect of selected essential oils (EOs: α-pinene, carvacrol, cinnamaldehyde, D-carvone, eucalyptol, L-linalool, L-menthol, L-menthone, (R)-(+)-limonene, and thymol) on H. solani growth. All EOs inhibited pathogen growth, but their antifungal activities differed significantly. Thymol, carvacrol, and cinnamaldehyde had the strongest inhibitory effects on mycelial growth under in vitro conditions. (R)-(+)-limonene displayed the weakest inhibition. The effectiveness of those EOs with the greatest antifungal activity was confirmed by in vivo experiments. EOs were applied through dressing and fumigation, with EOs bound to a biopolymer for dressing. Dressing and fumigation brought a highly statistically significant reduction in H. solani infection intensity and sporulation intensity on tubers. Although EOs had an insignificant effect on potato cooking quality, the taste of EO-dressed tubers was degraded by an off-odor and off-taste. EOs could provide an ecological alternative for reducing H. solani tuber infection during storage.

Fusarium dry rot of potato may be caused by several species of the genus Fusarium. This study aimed to evaluate the effect of essential oil (EO) components (α-pinene, carvacrol, cinnamaldehyde, D-carvone, eucalyptol, L-linalool, L-menthol, L-menthone, (R)-(+)-limonene and thymol) on the growth of Fusarium solani var. coeruleum using in vitro and in vivo experiments. All the evaluated EO components had a significant effect on the pathogen growth inhibition. Under in vitro conditions, the strongest inhibitory effect on mycelial growth was recorded for carvacrol, thymol, L-menthol and cinnamaldehyde. In vivo experiments confirmed the efficacy of selected EO components. The application of EO components was done by tuber dressing and fumigation. After treating tubers with EO components by dressing and fumigation, a statistically highly significant reduction in tuber infection with the pathogen was observed. Dressing usually had a stronger effect on the reduction in pathogen tuber infection (56.07–81.44%) compared to fumigation (40.03–69.63%). EO components did not have any significant effect on the organoleptic characteristics of cooked tubers; however, during tasting, a deteriorated quality of EO component-dressed tubers was found due to the off-odor and taste of the applied EO components. EO components have a high potential for ecological tuber protection against F. solani var. coeruleum during storage.