APS Homepage

POSTERS: Abiotic interactions

Pythium sylvaticum delays soybean emergence and increase seed loss at high soil moisture.
Mauricio Serrano - Iowa State University. Alison Robertson- Iowa State University, Sotirios Archontoulis- Iowa State University

Pythium sylvaticum is an Oomycete causing damping-off of soybeans in the Midwest of the United States. A growth chamber experiment was performed to determine the effect of soil moisture and inoculation with P. sylvaticum on the rate of soybean emergence and percent seed loss. Soybeans were planted in cups filled with vermiculite and either a layer of P. sylvaticum-infested millet or sterile millet, used as a control. Soil moisture was kept at 10% volumetric water content (VWC), 22% VWC, or 40% VWC to simulate water deficient, field capacity, and saturated soil conditions, respectively. The cups were placed in a growth chamber at 18ºC with 12 hours of daylight. Emergence was recorded daily for 21 days. Days to 50% emergence and percent seed loss (seeds not emerged) were calculated. In the absence P. sylvaticum, 50% emergence occurred after 6.6 days at 22% VWC and was slightly delayed at 10 and 40% VWC. Percent seed loss was minimal (10% seed loss) under optimal moisture conditions (22% VWC), and increased slightly at 10 and 40% VWC. The presence of the pathogen delayed emergence at all soil moistures and under saturated conditions (40% VWC), 50% emergence was not achieved by 21 days. In the presence of the pathogen, the increase in soil moisture also increased seed loss, which reached a maximum of 66% under at 40% VWC. These data on the effect of soil moisture on soybean emergence and damping-off caused by P. sylvaticum will contribute to efforts to develop a model for soybean seedling disease in the Midwest.