Risk assessment of six commercial mycorrhizal products: Opinion of the Panel on Plant Health of the Norwegian Scientific Committee for Food and Environment

Mycorrhiza is a beneficial association between plant roots and fungi. This mutualistic symbiosis is essential for plant growth in most natural terrestrial ecosystems and in agriculture. Commercial mycorrhizal products containing fungi and bacteria may promote plant growth, especially on sites without a natural microbial community. Due to the risk of unintended negative effects, introduction of new species or genetically different isolates of native species should always be considered carefully. This report assesses the risk of establishment and spread of six fungal species and six bacterial species included in different commercial mycorrhizal products, as well as the species’ potential impact on Norwegian biodiversity. Most of the evaluated fungi and bacteria are probably present in Norway, even though presence at present data only exist for two of the six fungal species. Establishment of the assessed fungi on the plants and sites where they are applied is considered moderately likely, with medium uncertainty, while establishment of the bacterial species is considered to range from very unlikely to very likely depending on the bacterial group, with low uncertainty. The probability of spread to the wider environment ranges from unlikely (four fungal species), to moderately likely (two fungal species), to very likely (five of the six bacterial species). However, for all species it is considered unlikely that establishment and spread would have negative effects on other native species, habitats and ecosystems in Norway.