Jared M. LeBoldus and
Peter V. Blenis, Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2H1, Canada;
Barb R. Thomas, Alberta-Pacific Forest Industries Inc., Boyle, AB T0A 0M0, Canada;
Nicolas Feau, INRA, UMR BioGeCo, BP 81, 71, Avenue Edouard Bourlaux, 33883 Villenave d'Ornon Cedex, France; and
Louis Bernier, Centre d'Étude de la Forêt, Université Laval, Québec, QC G1V 0A6, Canada
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Accepted for publication 5 July 2009.
A greenhouse inoculation experiment and field study were conducted to determine the cause of an outbreak of Septoria musiva cankers on Populus balsamifera in a northern Alberta plantation. Four clones of P. balsamifera, five clones of putatively resistant P. deltoides, and one susceptible hybrid poplar clone, Northwest, were inoculated with seven isolates identified as S. musiva. Four of the isolates were from P. balsamifera in Alberta and the others were from P. deltoides in Quebec. Results indicated that disease severity was similar for Alberta and Quebec isolates (P = 0.243) and that P. balsamifera had the greatest mean disease severity (x-bar = 4.20), P. deltoides had the lowest (x-bar = 2.76), and Northwest was intermediate (x-bar = 3.45). A genetic analysis comparing six polymorphic polymerase chain reaction restriction fragment length polymorphism loci and the mitochondrial small subunit ribosomal DNA sequences of the seven isolates indicated that the Alberta population was made up of at least three distinct genotypes. Canker incidence and age on Northwest and 56 different clones of P. balsamifera in a plantation were recorded. Canker incidence (P = 0.726) and the canker age distributions (P = 0.994) were similar for the two species. In conclusion, contrary to what has been reported in the literature, P. balsamifera appears to be quite susceptible to Septoria canker.
© 2009 The American Phytopathological Society