Negative influence of non-host plants on the colonization of Pisum sativum by the arbuscular mycorrhizal fungus Glomus mosseae

We studied the influence of the arbuscular mycorrhizal (AM) non-host plants Stellaria media (Caryophyllaceae), Chenopodium album and Spinaceae oleracea (Chenopodiaceae), Brassica campestris, B. nigra, Capsella bursa-pastoris and Sisymbrium altissimum (Brassicaceae), Juncus balticus (Juncaceae), Urtica dioica (Urticaceae) and of the AM host plant Taraxacum officinale (Asteraceae) on the colonization of Pisum sativum by the AM fungus Glomus mosseae. None of the non-host plants tested were colonized by Glomus mosseae. Older non-host plants competed with P. sativum. No inhibition of AM colonization was observed in host plants that were grown in the same pot and at the same time as non-host plants. However, when non-host plants were grown for 30 d before P. sativum, they inhibited mycorrhizal colonization of the latter. In a split pot system the presence of U. dioica on the left-side decreased AM colonization of P. sativum roots on the left-side, but not on the right-side. Non-host plants decreased the inoculum potential of G. mosseae and in some cases the percentage AM colonization of host plants cultivated after non-host plants. These results indicate that roots of non-host species have factors that seem to affect the AM fungus before it establishes in the root of host plants.