BACTERIAL INTERFERENCE WITH INVITRO ASSAYS OF TALL FESCUE SEEDS FOR ACREMONIUM-COENOPHIALUM

In vitro embryo-derived callus culture is an efficient and useful technique for determining viable fungal endophyte (Acremonium coenophialum Morgan-Jones & Gams) levels in tall fescue (Festuca arundinacea Schreb.) seed lots; however, the presence of a yellow-pigmented bacterium occasionally interferes with detection of the fungus. The objectives of this study were to control and identify this bacterium. Excised embryos from 26 seed lots were plated on Schenk and Hildebrandt medium amended with 20-mu-M dicamba (2-methoxy-3,6-dichlorobenzoic acid); bacteria-infested seeds were found in 22 lots. Infestation levels ranged from 1 to 100%. Medium supplemented with 50 mg L-1 streptomycin eliminated bacterial growth without interfering with the growth of A. coenophialum. Based on microscopy, biochemical tests, and fatty acid analyses, the bacterium was identified as an Erwinia species with characteristics of the herbicola group.