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Pathogenicity, Incidence, and Distribution of Fungi Causing Root Rot in Idaho Sugar Beet Storage Piles

Carl Strausbaugh: USDA ARS NWISRL

<div>Fungal rots in sugar beet roots held in long-term storage can lead to considerable loss, but the distribution and incidence of fungal rots inside sugar beet piles and pathogenicity for some species is poorly understood. Thus, Idaho sugar beet held in 5 outdoor and 2 indoor piles in 2014 and 2015 were investigated by assessing the root surface area covered by fungal growth and discolored tissue in 9 one-meter square areas per pile using a stratified random sampling design. Pathogenicity was evaluated indoors via plug inoculation in 2015 and 2016. <em>Botrytis cinerea</em> covered 6-22% of root surface area in indoor piles, while outdoor piles averaged only 0-3%. The 2 outdoor Adelaide piles had less <em>Athelia</em>-like basidiomycete (avg. 0-2%) than other piles (4-15%), while no trends were evident for <em>Penicillium</em>-like spp. (0-8%). <em>Penicillium</em>-like spp. isolated: 60% <em>P. expansum</em>, 34% <em>P. cellarum</em>, 3% <em>P. polonicum</em>, and 3% <em>Talaromyces rugulosus</em>. There were no trends or differences based on sample location in a pile, but the 2 outdoor Adelaide piles had more healthy tissue (90-96%) than other piles (28-80%). <em>B. cinerea</em> was the most pathogenic (<em>P</em>><em>F</em> <0.0001) species (avg. 61 mm of rot) followed by <em>P. polonicum</em> and <em>P. expansum</em> (35 mm), <em>P. cellarum</em> (28 mm), <em>Athlelia</em>-like basidiomycete (22 mm), and <em>T. rugulosus</em> and the non-treated check (0 mm). Two outdoor piles had negligible fungal growth through proper management, but the management of fungal rot in other piles could be improved.</div>