PRODUCTION OF INDOLE-3-ACETIC-ACID BY MUTANT STRAINS OF USTILAGO-MAYDIS (MAIZE SMUT HUITLACOCHE)

Production of indole-3-acetic acid (IAA) by four strains of the maize pathogen Ustilago maydis was analyzed. The fungus induces gall formati on on its host plant and IAA production by U. maydis may be required a s a pathogenicity or virulence factor. The study included the FB2 wild -type strain and the 103, 130FZ and 130FT mutants. Results show that t reatment with clofibric acid, alone or in combination with UV light, c an be used to obtain U. maydis strains with defective IAA production i n vitro, as quantified with the Salkowski reagent and by HPLC. The str ain with the lowest production was 130FT, and its peak IAA level repre sented only 16% of the highest value obtained for the FB2 wild-type st rain (124 mu g/ml).