BONARES | ORDIAMUR- Overcoming replant disease by an integrated approach

Beteiligte Institutionen der FZ:GEO:

• Institut für Bodenkunde

Replant disease, also described as soil decline, is known for centuries, however, up to now the ultimate causes are unknown. After repeated growing of the same plant species, the soil loses its capacity to produce plants of the respective species. Poor vegetative development, stunted growth and reduced yield are visible plant reactions. In annual plants, crop rotation and change of cultivation sites are strategies to overcome replant disease. But these strategies 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, and could serve as a model of replant diseases in general. The replant diseased soils can not be used for up to 20-30 years, unless soil disinfection is applied. But the disinfectants are ecologically harmful, and the development of alternative approaches is absolutely essential to maintain a sustainable soil productivity. Within the project ORDIAmur this shall be achieved by an integrated approach that aims at understanding and controlling the processes in the rhizosphere that are induced by the plant. The participants of this consortiums have selected apple as the common, main model plant, due to the accessibility of the whole genome sequence and the economic relevance as the most important fruit crop in Germany. Other plant species will be integrated in the following phases. Replant disease is assumed to be caused by chemical components that are derived from the inducing plants, either by root exudates or by decomposition of dead plant parts. These substances will be identified and analysed spatially and temporarily. The resulting changes of the rhizosphere and subsequently the bulk soil biome regarding the species spectrum, and their relative abundance and function, will be characterized in depth using modern next generation sequencing techniques. The interaction of different groups of organisms, mainly nematodes, fungi, oomycetes and bacteria within and among each other and with the plant will be studied. The specificity of root exudates, decomposition of plant parts, and interaction of organisms will be elaborated in soils, differing extremely in composition. The prerequsites for these investigatons are given by the participation of different institutions and private companies owning long-term field experiments. Other investigations are focussed on the responses of plants grown in replant diseased soil, which should allow to identify rootstock genotypes that either are less sensitive to replant disease or that induce replant disease to a lesser extent. Besides this strategy, the application of antagonistic microorganisms, that will be identified in the first phase of ORDIAmur, may shape the soil biome composition in a way that soil health is maintained or regenerated. Furthermore, beneficial endophytes, that protect plants against stress caused by replant disease, shall be isolated, characterized and used as inoculant to improve plant health and growth. Decisive stimuli are expected from the socio-economic analysis of the replant disease situation and the management strategies developed by this consortium. Tools for communication of knowledge in formats immediately applicable by farm decision makers and policy makers will be developed. The transfer into public will contribute to implement sustainable, ecologically beneficial and economically applicable tools to overcome replant disease, and are intended to be used by public authorities to achieve the goals of BonaRes in Germany and worldwide.