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BonaRes (Modul A):


Overcoming Replant Disease by an Integrated Approach

A joint project of the BMBF research initiative: BonaRes - Soil as a sustainable resource

Apple replant disease

Aims of ORDIAmur

The apple replant disease has been known for a long time, but is a phenomenon that is not scientifically understood: with replanting, the soil loses its ability to serve as a substrate for plants of the same species and to provide consistently high yields. If the diseased soil is not disinfected, the replant disease persists for 20 to 30 years. The disinfection methods are based on thermal and chemical processes, which are costly and ecologically controversial or no longer permitted.

Based on the knowledge gained in ORDIAmur about the development of the replant disease, urgently needed management measures for the restoration of soil health shall be developed.

In the first project funding phase a biotest for the detection of apple replant was developed. Further results are to be mentioned: The replant disease is immobile and local. The composition of the soil microflora and soil microfauna changes structurally and functionally in replant soil. Early indicators of apple replant disease were identified at plant level, e.g. root development.

The ORDIAmur project aims to characterize the specific changes in the soil caused by the development of the disease by analyzing root exudates and the rhizosphere biome. The soil properties will be taken into account.

New sequencing techniques allow to detect not only the species diversity but also the abundance of different organisms. The measurements of the plant reaction to replant soil is another focus. The different genotypic tolerance and age of the plant should help to develop management strategies.

New ways to overcome the replant disease are also expected from the identification of microorganisms that are causally involved in the induction and from the species that show antagonistic effects.

The socio-economic analysis of the situation and the approaches to overcome the disease will provide decisive support. The development and transfer of communication tools for decision-makers and for practical application should contribute to the implementation of sustainable, environmentally friendly and economically feasible measures to overcome the replant disease.

Apple root development in healthy and replant soil (photo: K. Smalla/D. Vetterlein)

Biotest of apple plants in the greenhouse (photo: Felix Mahnkopp-Dirks)