Stemphylium blight (SB) (Stemphylium botryosum) is a major disease of lentil (Lens culinaris Medik.) in many global production regions. In Canada, SB typically occurs after canopy closure in the ...second half of the growing season when weather conditions become warm and humid. Experiments were carried out to assess the impact of SB disease on milling qualities of lentil. In 2014, milling qualities of red lentils were compared between seed obtained from an uninfected site and those produced at a naturally SB‐infected site. In 2016 and 2017, controlled field experiments were conducted by artificially inoculating the plots with SB conidia at the early flowering stage. Seed yield in the infected plots was reduced by 52, 22, and 30% compared with control plots in 2014, 2016, and 2017, respectively. The percentages of stained and deformed seeds were increased in infected plots in 2016 and 2017. Seeds infected with SB have reduced milling qualities. Dehulling efficiency was reduced by 25.3, 23.0, and 15.9%, and milling recovery was reduced by 23.7, 25.4, and 15.1% compared with the uninfected control plots, respectively, in 2014, 2016, and 2017. Stemphylium blight had minimal impact on football lentil recovery. These results suggest that SB is potentially the leading cause of the reported poor milling quality of Canadian red lentils that reduces the economic value in years when the growing season is favorable for development of SB. These results have major implications for agronomy, pathology, and breeding strategies of the lentil crop in temperate production regions.
Aphanomyces root rot, caused by the soilborne oomycete
Drechs., has developed into a serious disease in the pea- and lentil-producing areas of the Great Plains of North America. Based on six pea ...differentials previously used to differentiate 11 pathotypes in France, pathotypes were identified among field isolates from Saskatchewan (14) and Alberta (18). Four isolates from the U.S.A. and standard isolates for pathotypes I and III designated in the French study were also included. Each isolate was tested twice in replicated experiments by inoculating French pea differentials 'Baccara', 'Capella', MN 313, 902131, 552, and PI 80693, along with the Canadian susceptible pea cultivar 'CDC Meadow' and partially resistant USDA line PI 660736 under controlled conditions. Pea plants grown in vermiculite were inoculated 10 days after seeding by pipetting 5 ml of a suspension containing 1 × 10
zoospores ml
to the base of each plant. Root discoloration was scored 10 days postinoculation using a 0 to 5 scale. Testing revealed that 38 of the isolates, including standard pathotype I isolate RB84, belonged to pathotype I; four isolates including standard pathotype III isolate Ae109 were pathotype III; and U.S.A. isolate Ae16-01 was a pathotype II isolate. An alfalfa isolate from Quebec was avirulent on all pea genotypes. These findings indicate that pathotype I is predominant on the Canadian prairies.
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.
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