VARIATION IN THE PRODUCTION OF ASCOCHITINE BY ASCOCHYTA-FABAE

Ascochitine was produced in culture by 18 of 19 isolates of Ascochyta fabae. Production was maximal at 20 degrees C on Czapek Dox nutrients supplemented with hot water extracts of the host plant, Vicia faba, an d varied from 7.8 to 86.0 mg l(-1). High titres were obtained in shake culture but not in still culture unless the surface to volume ratio w as large. Two isolates failed to synthesize ascochitine after repeated subculture but production by one of these was restored after passage through V. faba. Passage increased mean production of 16 isolates from 42.8 to 68.1 mg l(-1).