ERA-NET C-IPM: A holistic approach for the management of crazy (hairy) root disease, caused by rhizogenic Agrobacteria in tomato, cucumber, and eggplant cultivation (C-RootControl)

• Forschungsstelle: BLW
• Projektnummer: 12.04_1
• Projekttitel Englisch: ERA-NET C-IPM: A holistic approach for the management of crazy (hairy) root disease, caused by rhizogenic Agrobacteria in tomato, cucumber, and eggplant cultivation (C-RootControl)

Schlüsselwörter (Deutsch)

Haarwurzelkrankheit, Gartenbau, integrierter Pflanzenschutz

Schlüsselwörter (Englisch)

Hairy root disease, horticulture, integrated pest management

Schlüsselwörter (Französisch)

maladie chevelu racinaire, horticulture, protection des plantes intégrée

Kurzbeschreibung (Englisch)

 “Hairy or crazy root disease” (HRD) is characterized by extensive root proliferation and occurs on several dicotyledonous plants, among which many economically important crops. Since the early 1990s, hydroponically grown cucumber plants, and later tomato crops and eggplants, have been affected by the disease, causing substantial economic losses. HRD is a rapidly spreading disease, with an increased prevalence in several European countries. In addition, HRD is a highly persistent disease because rhizogenic Agrobacteria can form biofilms around plant roots and in the irrigation system. Biofilms are difficult to remove because they provide a niche where microbes are protected against disinfectants. Therefore, high concentrations of chemicals are required to remove biofilm. Moreover, several chemicals are converted to toxic by-products, which has led to the awareness that the use of chemical biocides should be replaced or reduced. Therefore, there is clearly a need for integrated pest management (IPM) strategies to control HRD, especially because of (i) the rapid spread and high persistence of this disease; (ii) the current lack of sustainable and effective plant protection products; and (iii) the economic losses associated. IPM takes advantage of all appropriate pest management options, with minimum use of chemical pesticides.

The main objective of this project is to develop long-term sustainable IPM solutions allowing to reduce the problems attributed to HRD. To achieve this, a holistic approach will be adopted, in which plant cultivation, irrigation system (biofilm), and the plant microflora are included. Specific scientific objectives and expected outcomes include the development of a reliable monitoring tool for rapid detection of HRD, screening for new biocontrol organisms, evaluation of novel anti-biofilm compounds, and new cultivation techniques to reduce disease symptoms. In addition, a close interaction with stakeholders at a transnational level will be established. The project will work to raise awareness in the target group will be risen and growers and advisors will be informed regarding IPM strategies.

Publikationen / Ergebnisse (Englisch)

The main objective of this project is to bring the existing knowledge of the participating research groups together, stimulate collaboration between European research groups that are working on HRD and organize joint research in order to explore new and environmental-friendly treatments or cultivation techniques and to develop an integrated pest management strategy. To achieve this, we propose a holistic approach, in which the problem is tackled at different levels: (i) at the level of the plant by looking at new cultivation methods and techniques to prevent economic losses due to HRD; (ii) at the level of the root microflora, by screening for biocontrol organisms (BCOs) with antagonistic activity towards rhizogenic agrobacteria that can be applied in the plant rhizosphere; and (iii) at the level of the irrigation system, where new and innovative strategies to prevent biofilm formation are examined.

In work package 1 (WP1), the diversity of several European rhizogenic Agrobacterium isolates is examined using a multilocus sequence analysis (MLSA), and several phenotypic analyses, including assessment of biofilm formation capacity, catalase activity, and tolerance towards peroxide. Next, a selection of 20 representative isolates were subject to whole genome sequencing. Whole genome comparison revealed interesting differences among the different strains regarding chromosomal as well as plasmid-borne genes.

In WP2 innovative and sustainable techniques to treat Agrobacterium-containing biofilms in the irrigation systems are evaluated. Eleven commercial and 5 novel non-commercial were screened at lab-scale (preventive and curative effects were evaluated). For some compounds, the results are highly promising, considering the low BIC50 values (concentration for which the biofilm is reduced with 50%). In addition to the compounds, previously identified BCOs were also evaluated regarding their efficacy to prevent Agrobacterium biofilms. Preliminary results indicate that the tested BCOs are able to reduce the number of free-living and biofilm-associated agrobacteria in the water circuit of the pilot-scale system, which demonstrates their potential to use in practice.

In WP3 we screened for new BCOs with antagonistic activity towards rhizogenic agrobacteria. Because of the huge phenotypic and genotypic diversity of the rhizogenic agrobacteria, it is possible that some Agrobacterium isolates are not sensitive to the previously identified BCOs. It is therefore desirable to have a set of BCOs that exert different modes of action. Indeed, a couple of promising BCOs were obtained, and will be further investigated in follow-up projects.

WP4 involved the improvement of cultivation techniques to reduce symptoms caused by HRD. It is unlikely that any chemical or biological control strategy will be able to remove rhizogenic bacteria completely. Therefore, additionally, specific cultivation techniques are required to suppress symptom expression in tomato, eggplant and cucumber crops. Cultivation techniques examined in tomato were evaluated in eggplant and cucumber. It seems that opening of the slabs, and to a lesser extent using transparent covers, were able to reduce HRD symptoms.

WP5 focused on validation activities in greenhouse experiments. This WP brings together the results obtained in previous WPs, and evaluates combinations of different management techniques. Throughout the project, results were disseminated to the stakeholders (WP6). This has resulted in peer-reviewed scientific papers, articles in professionally oriented journals, and presentations at scientific conferences. In addition, the stakeholders in the user committee are also informed regarding the progress of the project on a regular basis. Vulgarizing posters have been developed for the growers, containing relevant information regarding the disease symptoms, cultivation techniques that can reduce HRD symptoms, disinfection measures to be taken during cultivation and in between two growth seasons. And finally, the organization of a joint international symposium was one of the key successes in this WP, with around 160 attenders from different European countries.