Epichloë is not associated with the pollen of infected ryegrass plants

Abstract

Observations taken over decades of seed production, and examination of anther tissues from Epichloë infected grasses suggest that Epichloë endophytes are vertically transmitted through seed and are not horizontally transferred by pollen to new host plants. However, no study has quantified the potential for Epichloë transmission via pollen. We studied the incidence of Epichloë DNA detection in pooled pollen samples collected from subsets of 1680 Lolium perenne plants undergoing seed multiplications in a containment glasshouse. Most plants were infected with one of several Epichloë strains, representing different species of Epichloë. These data were compared with the incidence of Epichloë DNA in anthers, pseudostem and seed with known infection status. Sensitive qualitative and quantification assays, high resolution melting analysis and digital droplet PCR were employed to detect and/or quantify either Epichloë or Lolium DNA within plant-host tissues. Epichloë DNA sequences were not detected in any pollen samples tested. Epichloë is therefore unlikely to be spread between plants via pollen. In countries such as New Zealand, where genetically modified organisms are regulated, risks of potential spread into the environment associated with maternal compared to paternal transmission may affect regulatory decisions regarding the use of such Epichloë-grass symbioses outside of physical containment facilities.