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Investigating the distribution and diversity of Leptosphaeria maculans in northern Idaho

Justin Pickard: University of Idaho

<div><em>Leptosphaeria maculans</em>, the causal agent of blackleg in canola (<em>Brassica napus </em>L.), is a serious threat to oilseed production. Developing plant resistance to blackleg has been a major objective of many canola breeding programs. Previously overlooked in northern Idaho until 2011, blackleg has found a foothold among <em>Brassica</em> crops in this region. Blackleg poses a risk to the northern Idaho canola industry since virtually no selection has been previously carried out to identify disease resistance among locally adapted varieties. Although observed disease symptoms have been minor to date, with little progression into the upper canopy and very few stem cankers, the frequency of infection is widespread. In a survey of 46 canola fields in northern Idaho, 38 were found to display symptoms of blackleg. Isolates of <em>L. maculans</em> (130) and <em>L. biglobosa</em> (10) were recovered from these infected fields. Analysis of <em>L. maculans</em> isolates revealed an equal distribution of mating types, suggesting widespread distribution of ascospores and sexual recombination. Utilizing known plant resistance differentials and PCR, the diversity and distribution of avirulence genes was determined. Characterization of local blackleg races has allowed screening of the University of Idaho canola germplasm to find sources of genetic resistance that can be introgressed into high yielding canola lines with adaptation to northern Idaho environments.</div>