Non-host plants:Are they mycorrhizal networks players?

Common mycorrhizal networks(CMNs)that connect individual plants of the same or different species together play important roles in nutrient and signal transportation,and plant community organization.However,about 10%of land plants are non-mycorrhizal species with roots that do not form any wellrecognized types of mycorrhizas;and each mycorrhizal fungus can only colonize a limited number of plant species,resulting in numerous non-host plants that could not establish typical mycorrhizal symbiosis with a specific mycorrhizal fungus.If and how non-mycorrhizal or non-host plants are able to involve in CMNs remains unclear.Here we summarize studies focusing on mycorrhizal-mediated host and non-host plant interaction.Evidence has showed that some host-supported both arbuscular mycorrhizal(AM)and ectomycorrhizal(EM)hyphae can access to non-host plant roots without forming typical mycorrhizal structures,while such non-typical mycorrhizal colonization often inhibits the growth but enhances the induced system resistance of non-host plants.Meanwhile,the host growth is also differentially affected,depending on plant and fungi species.Molecular analyses suggested that the AMF colonization to non-hosts is different from pathogenic and endophytic fungi colonization,and the hyphae in non-host roots may be alive and have some unknown functions.Thus we propose that non-host plants are also important CMNs players.Using non-mycorrhizal model species Arabidopsis,tripartite culture system and new technologies such as nanoscale secondary ion mass spectrometry and multiomics,to study nutrient and signal transportation between host and non-host plants via CMNs may provide new insights into the mechanisms underlying benefits of intercropping and agro-forestry systems,as well as plant community establishment and stability.