Molecular Evidence of Mucoromycotina “Fine Root Endophyte” Fungi in Agricultural Crops

Over 85% of land plants engage in symbiotic relationships with mycorrhiza-forming soil fungi that colonise their roots. These associations, termed mycorrhizal symbioses, involve the exchange of fungal-acquired nutrients and water for photosynthetically fixed plant carbon. Mycorrhizal symbioses are thus considered a promising nature-based solution to making agricultural practices more sustainable, particularly by reducing the need for chemical fertiliser applications on soils while maintaining crop yields. In order to implement the widespread use of mycorrhizal fungi in agriculture, a complete awareness of their range of plant hosts is needed. Mucoromycotina Fine Root Endophytes (MFRE) are a group of mycorrhiza-forming fungi that, over the last decade, have been shown to be phylogenetically and functionally distinct from the common Arbuscular Mycorrhizal Fungi (AMF). Fungal morphologies similar to those of MFRE have been described in early light microscopy studies on roots stained for mycorrhiza. However, owing to limitations in the tools used to identify fungal endophytes until now, these structures were routinely misidentified as belonging to AMF. As such, the true range of plant hosts colonised by MFRE remains unclear. Here, we provide the first molecular evidence of MFRE colonisation within the roots of winter wheat, winter barley, spring wheat and strawberries. Root samples were collected from an Oxfordshire farm (UK) and were analysed for fungal symbionts using a workflow involving PCR with the NS1/EF3 universal fungal primer set and molecular cloning. Partial DNA sequences of the 18S ribosomal RNA gene were obtained and were analysed using BLAST. Our findings shed light on the true distribution of plant-MFRE associations and give rise to new questions regarding their functional significance within agricultural plants.