RESUMEN
Pectinolytic bacteria cause bacterial soft rot of potato tubers. The most significant losses occur during storage. The efficacy of essential oil (EO) components carvacrol, cinnamaldehyde, d-carvone, l-menthone, R-(+)-limonene and thymol was tested against Pectobacterium carotovorum subsp. carotovorum (Pcc) and Pectobacterium atrosepticum (Pa). Disc diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests were performed in vitro, as well as potato disc and whole tuber maceration tests in vivo. Under in vitro conditions, cinnamaldehyde was the most effective against both bacteria (MIC 0.5 µL/mL, MBC 1.5 µL/mL). Both bacteria were found to be more susceptible to d-carvone (MIC 1.5-2.5 µL/mL, MBC 2.5 µL/mL) and thymol (MIC 2.5-5 µL/mL, MBC 3-5 µL/mL). R-(+)-limonene was the least effective. Results from the potato tuber disc maceration test confirmed a significant antibacterial effect of cinnamaldehyde at a concentration of 1.5 µL/mL. No rotted area was observed on potato tuber discs after treatment with l-menthone at concentrations of 2.5 µL/mL and 10 µL/mL against Pcc. A more pronounced effect was obtained when carvacrol was used at concentrations of 5 µL/mL against Pcc and 10 µL/mL against Pa. Disease severity tests on potato tubers after soaking for 20 min at MIC concentration of the EO components followed by 7 days of incubation at room temperature and 15 °C confirmed the antibacterial activity of cinnamaldehyde (0.5 µl/ml), l-menthone (2.5 µl/ml) and carvacrol (5-10 µl/ml). Cinnamaldehyde, l-menthone, and carvacrol may be recommended for further testing to treat stored potato tubers.
RESUMEN
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.
RESUMEN
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.
RESUMEN
Two novel dsDNA bacteriophages named Pectobacterium virus CB251 (PcCB251) and Pectobacterium virus CB7V (PcCB7V) targeting plant pathogen Pectobacterium parmentieri have been isolated and sequenced. The PcCB251 genome consists of 40,557 bp with G+C content of 48.6% and contains 47 predicted genes on a single strand. The phage is classified in genus Berlinvirus, family Autographiviridae. The PcCB7V phage has a circular dsDNA genome of 146,054 bp with G+C content of 50.4% and contains 269 predicted protein genes on both strands and 13 tRNA genes. The PcCB7V phage can be classified in genus Certrevirus, subfamily Vequintavirinae. Both novel bacteriophages have narrow host ranges, but they extend the list of candidates for phage-based control of pectolytic bacteria causing soft rot disease of potato.