Indole Acetic Acid Production by the Fungal Endophyte of Tall Fescue

Abstract Increased plant growth and morphological alterations are characteristics of tall fescue ( Festuca arundinacea Schreb.) infected with a fungal endophyte ( Acremonium coenophialum Morgan‐Jones & Gams). A study was conducted to determine if there were ancillary plant growth regulators produced by the endophyte, which could account for these vegetative characteristics. Two endophytes, RRC 401 and RRC 347, were isolated from a rhizomatous and upright growing genotype of tall fescue, respectively. These isolates were cultured on laboratory medium, and extracts of this medium were examined for plant growth regulators using thin‐layer and gas chromatography. Only 3‐indole acetic acid (IAA) was detected in culture extracts of this fungus. The in vitro production of IAA by both isolates was confirmed by gas chromatography‐mass spectrometry. This was the first report of IAA production by this endophyte. Indole acetic acid production varied according to the strain, culture conditions, and age. Indole acetic acid in plant material was quantified with an immunoassay. Attempts to relate free IAA concentrations to altered growth expressions characteristic of endophyte‐infected and noninfected rhizomatous and upright growing genotypes of this grass were inconclusive.