Some effects of water potential upon endophytic Acremonium spp. in culture

Abstract

Acremonium coenophialum, A. starrii, and A. typhinum were grown on potato dextrose agar (PDA) amended with KC1 (PDA + KC1) 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 + KC1), 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 some isolates in PDA and in certain PDA + KC1 combinations. Inhibition zones were not detected on media adjusted to a water potential below about –3.5 to –4.2 MPa. Aerial hyphae were sparse on CMA + KC1 at –5.47 MPa or lower, facilitating visual observation of sporulation. Sporulation by some isolates occurred over the entire range of water potentials. Isolates varied in radial growth, production of inhibition zones, sporulation, and in production of halos within the media and these responses appear to be characteristic of the isolate rather than the species. Growth of an unknown Acremonium species from Stipa robusta was restricted at –2.33 MPa on PDA amended with sucrose.

Key Words:

• Antibiotic
• Festuca
• Hordeum
• sporulation
• Stipa
• water relations