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Description

Alfalfa (Medicago sativo) seeds are often planted when environmental conditions are optimal for Pythium seed rot and damping-off, which is caused by various different Pythium species. Pythium seed rot can devastate alfalfa stands requiring them to be completely replanted. South Dakota plants the second most acres of alfalfa in the United States, and surveys describing Pythium spp. causing disease on alfalfa in the state were lacking. In this study, putative Pythium isolates were baited from soil samples collected in eastern South Dakota using the rolled-towel technique. Pure cultures were obtained, and Pythium spp. were identified using ITS and cox1 sequences. The Pythium isolates were assessed for pathogenicity on alfalfa using a culture plate method. P. sylvaticum was the most frequently isolated alfalfa pathogen. Several commercial fungicides were evaluated against Pythium spp. using agar plate-based assays. CruiserMaxx (mefenoxam, fludioxonil, thiamethoxam) demonstrated strong activity against Pythium isolates. This study establishes the presence of a diverse array of Pythium spp. that are alfalfa pathogens in South Dakota, and the fungicide sensitivity tests provide growers with localized information to select effective fungicide treatments. Increased grower awareness to Pythium diseases of alfalfa may lead to better disease management and increased alfalfa yields in South Dakota.ds

Publication Date

2021

Identification and Characterization of Pythium Species Isolated From Commercial Alfalfa Fields in South Dakota

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