Overcoming Replant Disease by an Integrated Approach

Project number: 031B1070
Contact: Prof. Dr. Traud Winkelmann, Leibniz Universität Hannover
Mail: traud.winkelmann@zier.uni-hannover.de
Project team: Leibniz Universität Hannover, German Research Center for Environmental Health, Helmholtz Centre for Environmental Research – UFZ, Bonn-Rhein-Sieg University of Applied Sciences, Humboldt-Universität zu Berlin, Julius Kühn Institute, Horticultural Center Schleswig-Holstein, Leibniz Centre for Agricultural Landscape Research, Rheinische Friedrich-Wilhelms-Universität Bonn, Technische Universität Dortmund, Institut für Pharmazeutische Biologie - Technische Universität Braunschweig

Duration: 01/04/2022 - 31/03/2025
Link Website: www.ordiamur.de 

Project aim 
ORDIAmur aims at gaining a deeper understanding of the processes resulting in replant disease in order to develop tools for overcoming the disease. For the soil strategies to restore organismic communities will be established. On the plant site tolerant rootstocks shall be developed. 
Replant disease, also described as soil decline, is known since decades, the causes, however, are not understood. Poor vegetative development, stunted growth and reduced yield are visible plant reactions. In annual plants, crop rotation and partially changing the cultivation sites are measures to overcome replant disease. These possibilities are usually not available for woody species being produced in nursery and fruit production centers. Replant disease is of special importance for members of the Rosaceae family, but has also been reported for some other crops, e.g. vine. The replant diseased soils can not be used for up to 20-30 years, unless soil disinfection is applied. The used substances are ecologically harmful, and the development of other approaches is absolutely essential to maintain a sustained soil productivity. 
Expected results 

1.  Prediction of presence or absence of soil decline by bio-tests, plant and soil indicators.

2. Overcoming replant disease by:

       -> Measures to increase the microbial diversity in the soil

       -> Breeding of rootstocks with tolerance against replant disease

       -> Inoculation of plants with beneficial endophytes to achieve “immunization”

3. Implementation of operational innovations into considerations of social economic prerequisites.

4. Transfer of the ORDIAmur consortium results into public (internet platform).


project results so far


•    ARD develops on all soils, but its severity differs depending on soil characteristics with light (i.e. sandy) soils leading to more severe ARD

•    When grown in ARD soil, apple roots express an extraordinary stress response, which is characterized in detail in terms of the metabolites.
•    Root morphology and root endophytic communities undergo severe changes in ARD soils.
•    Isolated endophytic bacteria and fungi from roots grown in ARD soils are available and can now be tested for their interaction with the plant or

     potential causal agents
•    Among the proposed causal agents of the ARD disease complex, nematodes and their associated microbiome, bacterial genera in the

     rhizosphere (Streptomycetaceae and others) as well as inside apple roots (Streptomyces), fungal genera of the family Nectriaceae and

     oomycetes in the rhizosphere were identified as important actors.


The ORDIAmur consortium has gained relevant insights into ARD mainly in terms of unraveling the significant changes that occur under replant situations (including their spatial extent). These changes concern:
(i) microbial communities in the different microhabitats endosphere, rhizoplane, rhizosphere and bulk soil,
(ii) microbial functions,
(iii) soil biota of higher trophic scales, and (iv) plant reactions, especially concerning secondary compounds, and their genetic basis.

Furthermore, we started first field trials - amongst others in collaborating horticultural enterprises - to test ARD countermeasures.


Expected results phase  3               

In the third project phase, the focus will be placed even more strongly on user relevance. To this end, for example, around 150 farms will be contacted and their replant affected soils will be sampled. In a biotest, these soils will be tested for the severity of ARD. Thus, a comprehensive picture of the influence of various factors influencing ARD will be obtained and ARD indicators will be validated. In addition, various measures to overcome ARD are tested in some tree nurseries and apple orchards. From the knowledge gained, a "decision-support-tool" will be developed, which will enable users to assess the ARD risk and receive recommendations regarding possible countermeasures.

Overcoming Replant Disease by an Integrated Approach