The response of fine root endophyte (Glomus tenue) to waterlogging is dependent on host plant species and soil type

An increase in a form of arbuscular mycorrhizal (AM) fungi, termed fine endophyte or fine root endophyte (Glomus tenue (Greenall) I.R. Hall), is often observed under extreme environmental conditions. We investigated the influence of host plant species, waterlogging and landscape zone (soil type) on colonisation by fine root endophyte. Colonisation by AM fungi and fine root endophyte was measured in Lolium rigidum Gaudin (ryegrass) and Lotus subbiflorus Lag. (lotus) sampled from the upper, middle and lower/riparian zones of a sloping pasture. Ryegrass and lotus were then grown in a glasshouse in soil from these three zones: waterlogging was initiated for half the pots from day 43 and colonisation determined 35 days later. In the field, AM fungal colonisation was lowest in the lower zone for ryegrass only. In the glasshouse, waterlogging greatly decreased AM fungal colonisation, with the exception of lotus in lower zone soil where colonisation by fine root endophyte was prolific. Waterlogging impacts on plant growth were small. Fine root endophyte better withstands the stressful conditions induced by waterlogging than other forms of AM fungi, but this response differs with host plant. Further study of the environmental niche of fine root endophyte is necessary to understand its function under extreme conditions.