Optimizing Biocontrol Activity of Paenibacillus xylanexedens for Management of Hairy Root Disease in Tomato Grown in Hydroponic Greenhouses

Hairy root disease (HRD) caused by rhizogenic Agrobacterium biovar 1 strains affect tomato, cucumber, eggplant, and bell pepper grown in hydroponic greenhouses can cause considerable yield losses worldwide. Recently, Paenibacillus xylanexedens (ST15.15/027 AD117) with antagonistic activity against agrobacteria were identified. In this study, we present results of greenhouse trials two consecutive growing seasons (2019 2020) to examine the potential these biocontrol organisms (BCOs) under practical conditions. BCO-treatment at a 107 colony forming units (CFU)/mL density resulted reduction HRD infestation rate, confirming P. strains. Results revealed that single BCO strain (ST15.15/027) performed equally well as mixed inoculum both The same level was even achieved when reduced 105 CFU/mL. qPCR analysis further showed still rockwool substrate near end trials, indicating they persist environment application start trial is sufficient protect tomato plants until trial. Altogether, are highly valuable for optimization exploitation product control greenhouses.