TEMPERATURE-GROWTH RESPONSES DISTINGUISH THE OPC AND OPH SIBLING SPECIES WITHIN OPHIOSTOMA-PICEAE

The temperature-growth relationships of a range of isolates representi ng the recently identified OPC and OPH sibling species within Ophiosto ma piceae were studied. Most OPC isolates grew significantly faster th an OPH isolates on 2% Oxoid malt extract agar (MEA) between 17.5 and 2 7.5 degrees C, but between 27.5 degrees and 30 degrees growth rates of all OPC isolates studied declined rapidly in contrast to those of OPH isolates. The upper limit for growth of OPC isolates of MEA was ca 35 degrees, whereas that for OPH isolates was ca 31 degrees. A simple gr owth test at 32 degrees on MEA will discriminate between most isolates of the two species, and can be used as a supplementary aid to their i dentification.