SOME EFFECTS OF WATER POTENTIAL UPON ENDOPHYTIC ACREMONIUM SPP IN CULTURE

Acremonium coenophialum, A. starrii, and A. typhinum were grown on pot ato dextrose agar (PDA) amended with KCl (PDA + KCl) or sucrose (PDA S) to attain a wide range of osmotic water potentials. Radial growth was greatest between -0.3 MPa (PDA without amendment) and -3.0 to -4.0 MPa, below which growth diminished to near zero at -8 MPa. Acremonium isolates grew well on corn meal agar (CMA + KCl), but antibiotic and halo production were not detected on these media. Halos consisting of an unknown opaque deposit formed within the media around colonies of s ome isolates in PDA and in certain PDA + KCl combinations. Inhibition zones were not detected on media adjusted to a water potential below a bout -3.5 to -4.2 MPa. Aerial hyphae were sparse on CMA + KCl at -5.47 MPa or lower, facilitating visual observation of sporulation. Sporula tion by some isolates occurred over the entire range of water potentia ls. Isolates varied in radial growth, production of inhibition zones, sporulation, and in production of halos within the media and these res ponses appear to be characteristic of the isolate rather than the spec ies. Growth of an unknown Acremonium species from Stipa robusta was re stricted at -2.33 MPa on PDA amended with sucrose.