Aetiology of stemphylium blight on lentil in Canada

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