Effect of increased atmospheric CO2 concentration on powdery mildew and growth of soybean plants

Abstract

The increase in the concentration of atmospheric carbon dioxide (CO2) due to human activities can affect morphology and physiological processes in plants, as well as the cycle of the pathogens and their interaction with hosts. This study focused on evaluating the effect of high concentrations of atmospheric CO2 on the severity of powdery mildew (Microsphaera diffusa), and on the growth and nodulation of soybean. The experiment was conducted in open-top chambers (OTC) with and without CO2 injection, including a control with no OTC, corresponding, on average, to concentrations of 504 ppm, 429 ppm and 424 ppm, respectively, during the day. For 83 days, four soybean cultivars with different levels of resistance to powdery mildew were evaluated: FT-Estrela (highly susceptible), Embrapa 48 (susceptible), FT-Cometa (moderately resistant) and FT-5 (Formosa) (resistant). The increase of CO2 concentration resulted in increased disease severity of the four cultivars analyzed together, but there was no effect on pathogen sporulation. Furthermore, there was an increase in height, dry weight of roots and nodulation by Bradyrhizobium spp., except in Formosa cultivar. However, the dry mass of canopy did not differ segnificantly with increasing concentration of CO2. The development of the disease and the plant growth were higher in OTCs than outside them. The results show that increasing CO2 concentration affects the disease and there are differences in the responses among cultivars.