Management of hairy root disease in protected tomato crops: a biological and chemical approach

Abstract Hairy root disease (HRD), also known as “crazy roots”, caused by rhizogenic agrobacteria has in recent years become a serious problem in greenhouse hydroponic cultivation of tomato, eggplant and cucumber in many European countries. The typical symptoms include excessive development of roots, which leads to a more pronounced vegetative growth of the plants and production losses up to 10% and more. Once plants are infected, they cannot be remediated, since the disease symptoms result from the integration of the bacterial T-DNA into the plant host genome, which is irreversible. Due to the large genetic and phenotypic diversity of rhizogenic agrobacteria, a company-specific management strategy is recommended. Some strategies are based on reduction of the infection rate by inhibition of the growth of the agrobacteria in the irrigation system, while other techniques focus on reducing symptoms. In this study, we examined both biological and chemical strategies to reduce the number of agrobacteria in hydroponic tomato cultivation in order to reduce HRD incidence. In the biological approach, we tested three application strategies of a biocontrol organism (BCO), specifically a Paenibacillus strain with demonstrated antagonistic activity against rhizogenic agrobacteria. Although the BCO successfully established itself on the roots in two of the tested application strategies, disease symptoms still occurred. Molecular analyses of root samples suggested Agrobacterium needs to exceed a certain threshold to cause HRD incidence. Furthermore, a high BCO/pathogen ratio is needed to prevent HRD incidence. In the chemical approach, we examined the effectiveness of a single hydrogen peroxide application to the substrate before planting. Our results indicate that this strategy shows potential to reduce HRD in practice.

Publication year:2020

Accessibility:Open