Neotyphodium endophytes in tall fescue seed: viability after seed production and prolonged cold storage

This research quantified frequencies of Neotyphodium-infected (E+) tillers and mature seed from E+ plants of two wild tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire (= Festuca arundinacea Schreb.) accessions from the Mediterranean basin that were stored in the seed bank at the USDA, ARS Western Regional Plant Introduction (PI) Station, Pullman, Washington USA. Tiller-infection levels were high in glasshouse (>97%) and field (100%) plants of each accession and over 99% of the seed from E+ plants of both accessions harbored viable Neotyphodium endophyte. Seed germination was either slightly improved (Morocco accession) or not affected (Italy) by endophyte infection. High levels of viable E+ seed were produced by E+ field plants grown under a wide range of ambient temperatures (-27° to 37°C). These collective results suggest that viable endophyte is retained with current seed-regeneration practices at the Pullman PI Station. This study also documented viable Neotyphodium infection frequencies (16-100%) in plants grown from seed of 20 additional Mediterranean tall fescue accessions stored for four to ten years in the Pullman seed bank. For some of these accessions, low post-storage infection frequencies, in comparison with their high initial viability levels, suggested a decline in endophyte viability during seed storage. Additional evidence for diminishing endophyte viability levels in some accessions was provided by Polymerase Chain Reaction (PCR), immunoblot, and microscopic seed assays.