Germination stage effects susceptibility to infection of soybean by Pythium species
Rashelle Matthiesen: Iowa State University, Department of Plant Pathology
<div>Damping-off caused by <em>Pythium</em> species is an economically important disease of soybean in the United States. There are few data regarding the susceptibility of soybean germination stages to infection by <em>Pythium</em> species. The goal of this research was to compare the susceptibility of five soybean germination stages to infection by two <em>Pythium </em>species. Soybean germination stages include: (i) water imbibition (0-1 day after planting DAP), (ii) radicle growth (1-3 DAP), (iii) emergence (4 DAP), (iv) epicotyl growth (7 DAP), and (v) unifoliate leaf development (10 DAP). Seeds or root tips were inoculated with an agar slurry of <em>P. lutarium </em>or<em> P. oopapillum</em> at 0, 1, 2, 3, 4, 7, or 10 DAP and incubated at 23°C. Disease incidence and severity were assessed at 2, 4, 7, and 10 days after inoculation (DAI) by measuring lesion length. For <em>P. lutarium </em>and<em> P. oopapillum</em>, disease incidence was greatest when inoculation occurred at 1 DAP or 2 DAP, respectively. Root rot severity of seedlings inoculated with either <em>Pythium</em> species at 1 DAP and 2 DAP were more rotted compared to those inoculated at other DAP time points. Root rot severity of seedlings inoculated with <em>P. lutarium </em>and<em> P. oopapillum </em>was lowest when seedlings were inoculated 7 DAP and 10 DAP. These data improve our understanding of <em>Pythium</em>-soybean interaction and demonstrate that soybean is most susceptible to damping-off caused by <em>P. lutarium</em> and <em>P. oopapillum</em> within 2 days of planting when temperatures are at 23°C<em>. </em></div>
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