Development of a bacterial mixed culture preventing bacterial storage diseases of root vegetables

The storage of root vegetables is a critical aspect of agricultural production, significantly impacting both the quality and quantity of produce available for consumption. This study aimed to develop a bacterial consortium capable of preventing storage bacterial diseases in root vegetables. A total of 225 bacterial strains were isolated from various ecological niches, including crops, peri-root soils, coastal dune soils, sewage sludge, and symbiotic bacteria of common insect pests. These strains were characterized for their ability to grow at storage temperatures (4 °C) and produce cellulase, lipase, protease, and chitinase enzymes. From 225 isolates, 24 strains exhibited the highest enzymatic activities were selected for mutual inhibition assays, resulting in the selection of four strains (SP65, Dv004, Dv008, and Dv024a) that demonstrated high growth rates and enzymatic activities. The selected strains grew at 4 °C (OD₆₀₀ range: 0.061-0,190) and they exhibited the high intensity of production of the following enzymes measured as a halo diameter (cm) on bacterial medium: cellulase (from 1,4 to 1,8 cm), lipase (0,7) - 1,5), proteinase 1,2 - 1,6) and chitinase (0,3 - 0,4). These strains, identified as Stenotrophomonas maltophilia (SP65) and Serratia liquefaciens, were combined to form a bacterial consortium. The efficacy of this consortium was tested on potato (Solanum tuberosum L.), carrot (Daucus carota L.), celeriac (Apium graveolens L.), parsley (Petroselinum crispum Mill.), and onion (Allium cepa L.). The mixed culture was tested against bacterial soft rot pathogens including Pectobacterium carotovorum, Kosakonia cowanii, Enterobacter cloacae subsp. dissolvens and Burkholderia cepacia. For celeriac and parsley, the effect of inhibition of Pectobacterium carotovorum, Burkholderia cepacia, E. cloaceae subsp. dissolvens, Kosakonia cowanii, and the mixture of those pathogens were observed when pathogens were applied at concentration of 1,3 × 10⁸ CFU mL⁻¹. In case of onion the same effect of inhibition of growth of pathogens were observed only for P. carotovorum, and for B. cepacia at concentration of 1,3 × 10⁸ CFU mL⁻¹. The results demonstrated the potential of using a bacterial consortium as a biological control method to enhance the storage life and quality of root vegetables.