|Kaiser Jr, Walter|
Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/1996
Publication Date: N/A
Citation: Interpretive Summary: When isolations were made from plants grown from seed of sleepy grass (Stipa robusta) collected from 10 locations in New Mexico and Colorado, it was observed that 43 of 50 plants were infected with an endophytic fungus. The endophytic fungus belongs to the genus Acremonium. Plants infected with these endophytic fungi are known to have a narcotic effect on horses, hence the name sleepy grass. The Acremonium isolates from Stipa robusta are slow growing and spores produced by these fungi exhibited considerable variation in shape. Spores of most isolates were dead in cultures maintained at room temperature for 60 days. Serological tests demonstrated that the Stipa endophytes were related to Acremonium endophytes from other grasses.
Technical Abstract: Endophytic Acremonium isolates were obtained from 43 of 50 plants of Stipa robusta grown from seed collected from 10 locations in New Mexico and Colorado. Hyphae in the lower 2-3 cm of seedlings grown aseptically from infected seed were intercellular, about 2 um in diameter, mostly straight. Coarse sinuous or convoluted hyphae were produced in culture to some extent by many isolates and conidia were seen in all cultures. Observations of fungal structures were easily made on water agar. When first cultured, mean conidial lengths of individual isolates varied from 5.9 to 8.7 um. Considerable variation in conidial shapes occurred and average spore lengths of most isolates did not conform to described species, but were intermediate between A. starrii and A. coenophialum. The most common type of spore was too short for A. coenophialum and too long for A. starrii, and no isolate even faintly resembled A. chisosum. Spores of most isolates were dead in cultures 60 days old at 22 deg C. Serological analysis demonstrated the relatedness of the isolates to endophyte isolates from a broad range of other grasses.