Growth Inhibition of Mycorrhizal Fungi by Gibberellin

Abstract

tions by parasitic fungi. Since the survival of conifer seedlings often may be associated with the presence of mycorrhizal fungi on their roots (2), the loss of seedlings in the study by Kraus and Johansen could reflect gibberellin inhibition of the fungal symbiont. Levisohn (4) reported that pure cultures of Boletus granulatus, B. scaber and Rhizopogon luteolus had slightly decreased colony diameters when growing on agar media containing 100 ppm gibberellin. The present study was undertaken to observe the effect of gibberellin on liquid cultures of fungi which are known to form mycorrhizal associations with the roots of conifers (Hacskaylo, E., 1959, personal communication). The fungi were the basidiomycetes Amanita caesaria, A. rubescens, A. muscaria, Boletus luteus and B. bicolor and a representative of the Fungi Imperfecti, Cenococcum graniforme. The fungi were grown 14 days on Hoagland's medium (glucose, 20 g; KH2PO4, 1 g; MgSO,i7H20, 0.5 g; ammonium tartrate, 0.5 g; ZnSO4, 2.5 mg; 1 per cent ferric citrate chelate, 0.5 ml; thiamine HCl, 50 /jg; H20, 1 liter; pH adjusted to 4.5) in triplicate bottle-bead cultures (5) containing various levels of gibberellin (potassium gibberellate, Chas. Pfizer & Co.), TABLE I. The