Impact of Substrate Volumetric Water on Pythium aphanidermatum Infection in Petunia ×hybrida: A Case Study on the Use of Automated Irrigation in Phytopathology Studies

Abstract

Real-time irrigation monitoring and control afforded by dielectric soil moisture sensors allows for precise substrate volumetric water content (VWC) to be maintained under dynamic experimental conditions. A case study was conducted with Petunia ×hybrida ‘Dreams Red’ grown using a sensor-based irrigation system with half of the plants infected with Pythium aphanidermatum. Four soilless substrate moisture profiles were maintained postinoculation, with VWCs set at 0.2, 0.3, and 0.4 m3/m3, as well as a cyclic soil moisture profile that underwent a 0.25-m3/m3 change in VWC (0.18 to 0.43 m3/m3) between irrigation events. Once established, half of the plants in each trial were inoculated and grown out for one month under the defined irrigation regimes. The probability of root infection was lowered when VWC was maintained at 0.2 m3/m3 compared with 0.4 m3/m3 and cyclic (0.18 to 0.43 m3/m3) VWC. Mortality and biomass were unaffected by irrigation regime in both uninoculated and inoculated treatments. The soil moisture-sensor-based automated irrigation system was successfully able to maintain programmed irrigation profiles throughout the trial, under dynamic greenhouse conditions, increasing trust in the data and resulting conclusions of the study.