Menage a trois - are two fungi too much for ryegrass?

Abstract

A pot experiment investigated interactions between foliar endophytic (EP, Neotyphodium lolii) and root arbuscular mycorrhizal (AM, Glomus mosseae) fungi in Lolium perenne. The effects of three phosphorus (P) forms (KH2PO4-P, phosphate rock-P (PR) and phytate-P) on EP and AM colonisation and plant growth parameters were also assessed. AM arbuscular and vesicular structures were estimated by microscopic counting and fungal concentrations were quantified by qPCR of G. mosseae and N. lolii specific genes. Significantly more AM structures were formed in roots of EP-free compared to EP-infected plants, indicating that AM development is suppressed by the presence of foliar EPs. Total AM concentrations were also generally higher in EP-free plant roots, but not significantly. EP concentrations were significantly reduced by higher plant-available P in the growth medium, but mycorrhizal infection did not significant affect EP concentrations. Mycorrhizal inoculation increased shoot dry matter (DM) at low plant-available P in the PR treatment. Infection with the endophytic strain AR37 also significantly increased shoot DM and fungal concentrations were higher compared to CS (common or wild-type strain)- and AR1-infected plants. Insoluble phytate-P produced the same amount of biomass as soluble-P (K-Pi) did, suggesting that L. perenne has the ability to use organic P. Keywords: Neotyphodium lolii, Glomus mosseae, foliar endophyte, arbuscular mycorrhizae, Lolium perenne, qPCR, phosphate, AR1, AR37