Effects of elevated CO2 and temperature on interactions of zucchini and powdery mildew

Effects of increased CO2 and temperature on powdery mildew (Podosphaera xanthii) of zucchini (Cucurbita pepo), were evaluated under controlled conditions. Zucchini plants were grown in phytotrons under four different simulated climatic conditions: 450 ppm of CO2 at standard (18 degrees C night, 24 degrees C day) and elevated temperatures (22 degrees C night, 28 degrees C day), elevated CO2 (800 ppm) with standard temperature and elevated CO2 (800 ppm) with elevated temperature (4 degrees C higher than standard). Physiological responses of zucchini and pathogen development were studied. Under elevated CO2 both healthy and infected zucchini plants grew better when temperature was lower. Elevated CO2 generally caused no significant differences in pathogen development or disease severity, whereas elevated temperature stimulated the development of the pathogen. A combination of elevated CO2 and temperature always stimulated the development of the pathogen and disease severity compared to standard conditions.