Aetiology of stemphylium blight on lentil in Canada

Field isolates of Stemphylium spp. collected from lentil and nine other western Canadian crops were compared to the ex-type isolate of Stemphylium botryosum by morphology and by molecular phylogenetic analysis based on the internal transcribed spacer (ITS) and the glyceraldehyde-3-phosphate dehydrogenase gene regions. Sequence data of these genes for six other Stemphylium spp. obtained from GenBank were also included in the phylogenetic analysis. Morphology of colonies and morphometry of conidia agreed with previous descriptions of S. botryosum, but did not correlate with the clustering observed in the phylogenetic analysis. Sequence data revealed that S. botryosum is one of probably two Stemphylium spp. involved in the development of stemphylium blight on Canadian lentil, and is associated with other hosts such as faba bean, soybean, bean, pea, alfalfa, coriander, caraway and fenugreek. More than one validly described Stemphylium sp. was associated with the second cluster of isolates causing stemphylium blight, indicating that an extensive taxonomic review of the genus Stemphylium is required before this second stemphylium blight pathogen can be identified by name.