Neighbouring weeds differently influence arbuscular mycorrhiza in grapevine

Underground plant to plant communication is a complex and dynamic continuum of exchange of different chemical compounds, having a range of effects from inhibitory to stimulatory ones. This influences also the arbuscular mycorrhizae. We experimentally tested the influence of two selected weeds from Mediterranean Croatian vineyards on mycorrhizae development in neighbouring grapevine (Vitis vinifera L. cv. Plavac mali). The mycorrhizal parameters were compared between pots where there was only grapevine or Plantago lanceolata L. or Tanacetum cinerariifolium (Trevir.) Sch.Bip. alone and the pots with all combinations. Results during six months period showed that plant specie factor significantly influenced development of mycorrhizal intra- and extraradical mycelium and sporulation. Not only that different plant species differed but also grapevine mycorrhizal characteristics differed when combined with different neighbours. Grapevine and T. cinerariifolium individually and in combination generally enabled greater development of arbuscular mycorrhiza comparing to P. lanceolata individually and in combination with grapevine. This was visible in spores’ production, extraradical mycelium length and arbuscular mycorrhizal fungi (AMF) root colonization. Additionally, it was experimentally confirmed that Vitis vinifera L., Plantago lanceolata L., Taraxacum officinale Weber and Trifolium repens L. considerably differed in the composition of AMF community. These results showed that neighbouring plant species significantly influence grapevine’s arbuscular mycorrhizal symbioses establishment in pot cultures. It has implications for understanding real agroecosystems especially when it concerns the choice of appropriate cover crops. Results obtained here pose questions for our future research - Is the reason for observed differences the different AMF community promoted by different plant species or root exudation of stimulatory/inhibitory chemicals when in combination with other plant species or both? And what is the role of signalling compounds (SLs) in recognizing “suitable” neighbours?