Incidence and diversity of Neotyphodium fungal endophytes in tall fescue from Morocco, Tunisia, and Sardinia

There is a premium on having Neotyphodium germplasm available for temperate grass improvement programs because these fungal endophytes present opportunities for developing new grass-endophyte combinations for enhanced tolerance to abiotic and biotic stresses. Unfortunately; surveys have revealed a low incidence of Neotyphodium fungi in grass germplasm collections, This research surveyed tall fescue (Festuca arundinacea Schreb,) accessions from a 1994 Australian-U.S. plant-collection trip to Morocco, Tunisia, and Italy (Sardinia) for viable Neotyphodium fungi and determined whether infected accessions harbor different Neotyphodium genotypes. Conidial measurements of isolates cultured on agar and bioassays of die differential survival of bird cherry-oat aphid [Rhopalosiphum padi (L.)] on infected accessions were used to characterize Neotyphodium diversity. A secondary objective determined the consistency of a polymerase chain reaction (PCR) method to detect Neotyphodium fungi in fall, fescue. Neotyphodium was detected in 336 of 439 plants (76.5%) distributed among 104 accessions, of which 99 were endophyte-infected, Mean conidial lengths of 42 isolates ranged from 3.91 to 9.91 mum. Most of the isolates (71.4%) had conidia with mean lengths smaller than the lower limit (6.5 pm) characteristic of the tall fescue endophyte N. coenophialum (Morgan-Jones and Gems) Glenn, Bacon, and Hanlin. In aphid assays, ah endophyte-free plants were susceptible to R, padi and all but two infected plants were resistant to this aphid, Thus, a Mediterranean plant-collection trip secured diverse Neotyphodium endophytes in tall fescue for storage in seed brinks, and a PCR assay defected Neotyphodium in tall fescue plants of diverse geographical origin.