Effect of vitamins on growth and sporulation of Alternaria alternata (Fr.) Keissler.

Alternaria alternata, a leaf spot pathogen of beet (Beta vulgaris), was found to be auxoautotrophic for thiamine. On the other hand, riboflavin, biotin, inositol, and pyridoxine were heterotrophically needed for its growth. Vigorous sporulation was prominent in response to the additions of riboflavin, d-biotin, and inositol. A curiously depressent effect on both the growth and sporulation of the pathogen was noticed in presence of 1-ascorbic acid, folic acid, and nicotinic acid. These substances also lowered the pH of the medium towards acidity. Separate additions of thiamine, riboflavin, pyridoxine, biotin, and inositol, however, increased the pH towards the neutral and alkaline range.