INVITRO PRODUCTION OF PYCNIDIA BY SEPTORIA-TRITICI

The in vitro production of pycinidia by Septoria tritici was examined on six media reported to induce the formation of fruiting bodies. Among 26 freshly isolated cultures from various parts of the world, consistent differences in growth type were found which were only partially influenced by nutritional and environmental conditions. Cultures with yeast-like growth produced hardly any pycnidia or pseudopycnidia, while cultures with intermediate or mycelial growth types produced them frequently. Incubation in continuous darkness induced intermediate to mycelial growth types rather than yeast-like growth types in some cultures, and concomitantly the production of more pycindia. Potato-dextrose agar induced intermediate to mycelial growth types and production of (pseudo)pycinidia more often than V8 agar and wheat leaf extract agar, which had previously been reported to be especially beneficial to (pseudo) pycnidium formation by S. tritici. Isolates with a consistently yeast-like growth type, producing (virtually) no fructifications under any of the experimental conditions, were slightly stimulated to form pseudopycnidia on water agar supplemented with sterile pieces of maize, wheat or carnation leaves.