Potential Control of Potato Soft Rot Disease by the Obligate Predators and Like Organisms.

Bacterial soft rot diseases caused by spp. and spp. affect a wide range of crops, including potatoes, a major food crop. As of today, farmers mostly rely on sanitary practices, water management, and plant nutrition for control. We tested the bacterial predators and like organisms (BALOs) to control potato soft rot. BALOs are small, motile predatory bacteria found in terrestrial and aquatic environments. They prey on a wide range of Gram-negative bacteria, including animal and plant pathogens. To this end, BALO strains HD100, 109J, and a Δ derivative of HD100 were shown to efficiently prey on various rot-causing strains of and BALO control of maceration caused by a highly virulent strain of subsp. was then tested using a potato slice assay. All BALO strains were highly effective at reducing disease, up to complete prevention. Effectivity was concentration dependent, and BALOs applied before subsp. inoculation performed significantly better than those applied after the disease-causing agent, maybe due to consumption of glucose by the prey, as glucose metabolism by live prey bacteria was shown to prevent predation. Dead predators and the supernatant of BALO cultures did not significantly prevent maceration, indicating that predation was the major mechanism for the prevention of the disease. Finally, plastic resistance to predation was affected by prey and predator population parameters, suggesting that population dynamics affect prey response to predation. Bacterial soft rot diseases caused by spp. and spp. are among the most important plant diseases caused by bacteria. Among other crops, they inflict large-scale damage to potatoes. As of today, farmers have few options to control them. The bacteria and like organisms (BALOs) are obligate predators of bacteria. We tested their potential to prey on spp. and spp. and to protect potato. We show that different BALOs can prey on soft rot-causing bacteria and prevent their growth , precluding tissue maceration. Dead predators and the supernatant of BALO cultures did not significantly prevent maceration, showing that the effect is due to predation. Soft rot control by the predators was concentration dependent and was higher when the predator was inoculated ahead of the prey. As residual prey remained, we investigated what determines their level and found that initial prey and predator population parameters affect prey response to predation.