The Susceptibility of Populus trichocarpa Provenances in the Pacific Northwest to Septoria musiva and Septoria populicola Fung, Jason Chun-Yin
A Populus trichocarpa provenance trial in Harrison Mills had tested positive in 2009 and 2010 for Septoria musiva, a pathogen that reduces the photosynthetic activity of its host through necrotic spots on the leaf surface and has the potential to girdle and kill the host through cankers that develop on the branches and main stem. A closely related pathogen, Septoria populicola, has also been reported in the provenance trial; this particular pathogen is native to British Columbia and causes only non-lethal minor leaf lesions, but is impossible to distinguish from Septoria musiva without conducting DNA-based analyses. This study is aimed to assess the frequency of S. musiva and S. populicola infections on provenances of P. trichocarpa to determine if there is a pattern of differential susceptibility. The provenances of the P. trichocarpa extend from Alaska, through British Columbia and down into Oregon; these were grouped into two categories: a North and South population. The proportions of Septoria musiva and Septoria populicola infections were compared between the north and south populations to determine if there is a difference in infection proportions between the regions. The north and south proportions were also compared between 2010 and 2011. Although the number of infections were always higher in northern than in southern provenances, no significant differences were found between northern and southern infection proportions for Septoria musiva or Septoria populicola in 2010 or 2011. A comparison between regional infections in 2010 and 2011 was also not significantly different from one another for Septoria musiva. Although no significant differences was observed in the infection proportions of Septoria populicola between the southern populations over 2010 and 2011, a significant difference was observed in the infection proportions between northern regions in 2010 and 2011.
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