Neighbouring weeds influence the formation of arbuscular mycorrhiza in grapevine

Grapevine (Vitis vinifera L.) and two selected weeds from Mediterranean Croatian vineyards (Plantago lanceolata L. and Tanacetum cinerariifolium (Trevir.) Sch.Bip.) were examined in pot culture experiments, individually or when combined, to see whether multiple hosts influenced the formation of the symbiosis with arbuscular mycorrhizal fungi (AMF). The results after six-month period showed that plant identity and density significantly influenced development of mycorrhizal intra- and extraradical mycelium and/or sporulation. Grapevine and T. cinerariifolium individually and in combination resulted in a greater development of arbuscular mycorrhizae in terms of spore production, extraradical mycelium length and root colonization compared with pots containing P. lanceolata. Herbaceous weed species seemed to promote a different set of dominant AMF, potentially providing a wider spectrum of AMF for colonising grapevine roots. This indicates the value of encouraging host plant diversity in vineyards. AMF sequences obtained in this study are the first data reported for soils in Croatia.