The pattern of asexual sporulation in Mycosphaerella ligulicola

The asexual sporulation pattern of Mycosphaerella ligulicola Baker, Dimock & Davis was followed on agar culture. At 23°C pycnidial initials were laid down only in mycelium which was 10–30 h old. Spore production commenced in mycelium which was 18 h old and continued for at least 20 days. Where septate spores were produced, evidence suggested that septa were formed after abstriction of the spores from the sporogenous cells of the pycnidium. On agar medium and host leaf disks the spore number per unit area of culture increased with increase in temperature but spore size and the proportion of septate spores decreased. The increase in spore number was due primarily to a higher productivity per pycnidium. Total volume of the spore mass remained virtually unchanged over a wide temperature range. Within limits determined by temperature, illumination caused a reduction in spore size which was associated with a reduction in total volume of the spore mass.