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Population structure and genetic diversity of Melampsora spp. collected from Salix purpurea in the Northeast United States

Chase Crowell: Plant Pathology and Plant-Microbe Biology Section, Cornell University

<div><em>Melampsora</em> spp. willow rust is the most threatening disease of <em>Salix</em> spp. for short rotation coppice bioenergy feedstock production wherever shrub willow is grown. Investigations into this group of pathogens in the Northeast United States are ongoing to elucidate genotypic diversity and aid in successful disease resistance breeding. Previous work has identified two species, <em>M. americana</em> and <em>M. paradoxa </em>as the primary contributors to disease on <em>S. purpurea</em> in the Northeast. Single pustule isolates (n=184) were collected from wild and cultivated <em>S. purpurea </em>in NY, WV, VT, MI, and PA in 2015, and are being genotyped via genotyping-by-sequencing. Whole genome PacBio sequencing of a single <em>M. americana</em> isolate was performed in collaboration with the Joint Genome Institute’s Community Science Program to aid in variant discovery. Preliminary data from 95 samples suggest differentiation of isolates by location of collection, with two sites, Morgantown WV and Portland NY, showing highly diverged individuals. These data, in combination with previously performed detached leaf virulence assays across select host genotypes, will improve breeding efforts for targeted populations in the Northeast United States.</div>