METABOLISM OF ISOSTEVIOL AS A LOW SPECIFIC SUBSTRATE BY A WILD STRAINOF GIBBERELLA-FUGIKUROI

The metabolism of a wild strain of Gibberella fugikuroi was studied in presence of tetracyclic diterpenoid substances. The isosteviol was th e main compound used as a low specific substrate for the fungus. The m etabolic behavior of Gibberella in cultures supplied with 3.0 mM of is osteviol showed a fast consumption of this terpenoid inhibiting simult aneously the entire biosynthesis of the active gibberellins. Accumulat ion of Kaurenoic acid was also observed and the possible participation of 3-beta-hydroxylase blocking by the isogibberellins in the inhibiti on process was discussed.