While plant pathogenic bacteria are small, they can cause major problems in the greenhouse cultivation of vegetables and ornamental plants. Implementation of hygiene protocols, as well as the disinfection of greenhouses before growing new crops, can prevent the spread of the bacteria. Unfortunately pathogenic bacteria can sometimes escape all hygiene measures. That is why the Greenhouse Horticulture and Flower Bulbs Business Unit at Wageningen University & Research is investigating which sustainable, effective alternatives are available to prevent bacterial plant diseases in greenhouse horticulture crops.
Plant pathogenic bacteria are tough enemies. They multiply quickly and are able to determine when they are present in the sufficient number to attack a plant. They communicate with each other through signal molecules excreted by individual bacterial cells. Some bacteria, such as Agrobacterium tumefaciens or Rhizobium rhizogenes, are able to manipulate the plant's genetic information by inserting T-DNA into the plant. As a result, hormonal homeostatis of the crop is disrupted and it starts producing secondary metabolites (opines). These can be used almost exclusively by the bacteria as a food source.
Bacteria are present in all greenhouse cultivation systems. The majority of these single-cell micro-organisms is not harmful to the plant. These beneficial bacteria can even stimulate the growth of a crop. In resilient cultivation systems, the good microbial balance in substrate, water and around/in the plant is very important. To maintain this balance and at the same time prevent the spread of bacterial plant pathogens, new, sustainable strategies are needed, which can kill or inactivate plant pathogenic bacteria without the adverse effects on beneficial bacteria.
Within the current project, which started in 2019, Wageningen University & Research is investigating various strategies to combat the development of bacterial plant diseases. Firstly, the use of microbial enzymes. They might be used to prevent the formation of a biofilm of plant pathogenic bacteria on above and belowground parts of plantsand infection.
The second focus of the project is to understand how beneficial microbes can disrupt communication between plant pathogenic bacteria and thus make them less virulent. Possibilities for the use of parasitic bacteria, which prey on plant pathogenic bacteria, in greenhouse crops are also being explored.
Lastly, Wageningen University & Research is investigating whether increasing the resilience of the crop and cultivation system to bacterial diseases is possible. This could be achieved for example by treatments with chemical or microbial elicitors of plant's induced resistance or by inoculation of plant/growing substrate with micro-organisms, which are antagonistic to plant pathogenic bacteria.
At the moment research focuses on three pathosystems: Rhizobium rhizogenes and tomato (hairy roots disease) Acidovorax cattleyae in Phalaenopsis (brown spot of orchids) and Xanthomonas hortorum pv. pelargonii in Pelargonium (bacterial blight), but the knowledge about possible solutions obtained during this project is expected to be easily transferable onto other crops and bacterial pathogens..
The research is being carried out in collaboration with Glastuinbouw Nederland in the Netherlands and is funded by Topsector Tuinbouw & Uitgangsmaterialen, Stichting Kennis In Je Kas (KIJK), Stimuflori, ICL BV, Gennovation BV and ChiralVision BV.