Gibberellic acid, a metabolic product of the fungus Gibberella fujikuroi: Some observations on its production and isolation

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Abstract
Some strains of Gibberella fujikuroi (Saw.) Wr. (conidial state Fusarium moniliforme (Sheld.) emend. Snyder & Hansen) produce metabolic products with plant‐growth‐promoting properties. The capacity to produce such substances is common in rice‐infecting strains of G. fujikuroi; isolates from other hosts only infrequently produce such metabolites. From a selected rice‐infecting strain a plant‐growth‐promoting substance has been isolated in pure form. This substance, gibberellic acid, is distinct in chemical properties from the gibberellins described by Japanese investigators. In surface culture on Raulin‐Thom medium (2.5% sucrose) yields of 40 mg./1. are obtained in 14 days at 25°. In submerged aerated culture yields approaching 200 mg./1. are obtained on Raulin‐Thom medium (4% sucrose) in 18 days at 25°. Under such conditions, although gibberellic acid begins to appear in the medium during the latter part of the phase of active growth, at least 75%, and probably more, of the total final yield is produced after maximum dry weight has been reached and rapid uptake of sugar and ammonia‐nitrogen has ceased.