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Evidence for CYP51-mediated reduced sensitivity to triazole fungicides in Calonectria henricotiae

Jonathan Hulvey: Eastern Connecticut State University

<div>Boxwood blight, caused by <em>Calonectria </em><em>pseudonaviculata</em> and <em>C. henricotiae</em>, is a serious threat to <em>Buxus spp</em>. worldwide. Evidence for reduced sensitivity to triazole fungicides in <em>C. henricotiae</em> warranted comparative analyses of the <em>CYP51</em> gene in <em>C. henricotiae</em> and<em> C. pseudonaviculata.</em> BLAST searches of genomic contigs uncovered three <em>CYP51</em> paralogs, two of which, <em>CYP51A</em> and <em>CYP51B</em>, are known to mediate resistance to azoles. Phylogenetic analyses support the identity of the <em>CYP51</em> paralogs, which cluster with those from previously characterized fungal species. In the <em>CYP51B</em> coding sequence we identified only synonymous SNPs between <em>C. henricotiae </em>and<em> C. pseudonaviculata</em>, while comparison of the coding sequences of <em>CYP51A </em>uncovered non-synonymous SNPs, two of which are located in regions of the CYP51A active site that have been associated with azole binding. In addition, we report a premature stop codon in <em>CYP51A</em> of <em>C. pseudonaviculata</em>. These findings support a role for <em>CYP51A</em> in the reduced sensitivity exhibited by <em>C. henricotiae </em>and have implications for future management of boxwood blight.</div>