Promising Bacillus subtilis strains BZR 336g and BZR 517 for biocontrol of blackcurrant against Septoria leaf spot under unfavorable climate conditions

Septoria leaf spot is the most serious blackcurrant disease in Western Siberia. Two Bacillus subtilis strains BZR 336g and BZR 517 isolated in geographically distant locality (south of Russia) were evaluated for the blackcurrant disease suppression in field experiments (Western Siberia). The field trials were conducted on two cultivars differed by their susceptibility to Septoria ribis in two consecutive years differed by environmental conditions. As a rule, plant treatment with bacterial suspensions (105 and 106 CFU/ml) significantly (P < 0.05) reduced the disease severity compared with the untreated blackcurrant plants. In some cases, the effect of bacterial strains was comparable to that of chemical fungicide Topaz, CE 0.1%. Biological control of blackcurrant disease caused by S. ribis depended on B. subtilis strain, concentration of bacterial suspension, plant cultivars, and weather conditions. For the first time, we showed that B. subtilis strains isolated in a region with warm climate effectively suppressed the main blackcurrant disease in geographically distant locality with cold climate.