Taxonomic studies on monosporic pure cultures of Australian isolates of Stemphylium revealed the presence of three species, namely S. botryosum, S. globuliferum and S. vesicarium. A group intermediate between S. botryosum and S. vesicarium but more closely resembling S. vesicarium was recognised. The circumscription of S. vesicarium was broadened to accommodate this taxon which was found on Medicago sativa, M. rugosa and Simmondsia chinensis. Studies on herbarium specimens deposited as S. botryosum on M. sativa from a number of overseas locations indicated that in all cases the pathogen fitted our concept of S. vesicarium. Teleomorphs were induced in pure culture for each of the above-mentioned anamorphs, and in all instances the teleomorph was identified as Pleospora herbarum. The ascospore morphology was similar for all isolates, and the shape of the ends of the spore and the number of longitudinal septa were variable characters even within an isolate. However, the teleomorphs could be separated into two distinct groups on the basis of ascal length.
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