Impact of Pythium volutum Infections on Creeping Bentgrass Nitrate Uptake and Evapotranspiration Rate.

Pythium root dysfunction (PRD) is an important disease of creeping bentgrass (Agrostis stolonifera L.) in the southeastern U.S. Symptoms typically appear during the summer months as irregular patches of wilt or drought stress ranging in size from 6 to 40 cm in diameter. The mechanisms that drive symptom production in this disease are unknown, yet researchers have speculated that the pathogens impair creeping bentgrass nutrient and water uptake. Growth chamber and hydroponics experiments were established to measure nitrate and water uptake of creeping bentgrass roots in response to Pythium volutum infection. Creeping bentgrass (Penn ‘A-1’) was established in cone-tainers containing USGA sand and after eight weeks the plants were inoculated with a highly aggressive isolate of P. volutum. Four weeks after inoculation, a set of plants were transferred to a hydroponics system to measure nitrate uptake and evapotranspiration. Nitrate uptake and evapotranspiration rate was measured on separate sets of plants after 7, 14, and 20 days of heat exposure as well. Nitrate uptake was 50 to 65 % higher than non-inoculated controls on the 0 and 7 day sampling times, but rapidly declined after 14 days. After 20 days of heat exposure, creeping bentgrass plants that were inoculated with P. volutum exhibited 75 to 85% less nitrate uptake when compared to the non-inoculated controls. Evapotranspiration rate was similar among non-inoculated and inoculated creeping bentgrass plants. Creeping bentgrass roots infected with P. volutum have limited nitrate uptake when exposed to heat for 14 days and this is likely one of many mechanisms that drive PRD symptom production.