5P : Development of Phenotyping Protocols for Armillaria Root Rot in Prunus Rootstocks

Although rootstocks play a fundamental role in improving tolerance and resistance to diseases, water stress, and adaptation to difficult soils, only a limited fraction of the available rootstock diversity is currently used in orchards and breeding programs compared with grafted cultivars. Armillaria root rot, a disease causing rapid tree decline and mainly caused in France by the parasitic fungus Armillaria mellea, represents an increasing threat to French orchards. Current management strategies for this disease remain largely ineffective and rely primarily on preventive approaches such as crop rotation, soil fumigation, and stump removal, with no satisfactory chemical or biological treatments available.

Genetic improvement of Prunus to develop tolerant rootstocks appears to be the most promising strategy. This project aims to develop rigorous phenotyping protocols to evaluate rootstock tolerance to the disease under controlled conditions and to investigate the rhizosphere microbiome in order to identify potential components associated with tolerance. The study will combine in vitro and potted plant experiments, in which contrasting rootstocks will be exposed to different strains of A. mellea. The project also includes validation trials in infected orchards to assess whether results obtained under laboratory and greenhouse conditions are consistent with natural infection conditions in the field.