Biological control of major pathogenic bacteria of potato by Bacillus amyloliquefaciens strains SS-12.6 and SS-38.4

Potato is ranked as one of the most important food crops. Bacterial wilt caused by Ralstonia solanacearum and blackleg and soft rot caused by different species from genera Pectobacterium and Dickeya are considered two of the most important diseases of the potato. Biological control is the optimal strategy for controlling pathogens in crops generally, including bacteria. The present study aimed to evaluate the antagonistic effects of two Bacillus amyloliquefaciens strains, SS-12.6 and SS-38.4, against bacterial pathogens isolated from the potato in Serbia, such as R. solanacearum, Pectobacterium carotovorum, Pectobacterium brasiliense, and Dickeya dianthicola. The diameter of the inhibition zones formed by ethyl-acetate extracts of SS-12.6 and SS-38.4 strains show much higher values than the inhibition zones of supernatants, which implies the main power of these antagonists' potential lies in lipopeptides. The effectiveness of the treatment (19.7–44.5%), based on the difference in weight of potato tubers on the fifth and 15th day after treatment (DAT), showed that the antagonistic strains were almost equally effective in the suppression of P. carotovorum, P. brasiliense, and D. dianthicola strains. Strains SS-12.6 and SS-38.4 exhibited the efficacy in the suppression of R. solanacearum wilt from 28.64 to 60.22%. The analysis of the area under the disease progress (AUDPC) confirmed differences among pathogen control treatments and biocontrol treatments with B. amyloliquefaciens strains in all trials. This study shows that the two B. amyloliquefaciens strains, SS-12.6 and SS-38.4, can potentially be used as biocontrol agents against potato pathogens