Impact of Elevated CO2 and Temperature on Some Epidemiological Factors in Cochliobolus sativus,the Causal Agent of Spot Blotch in Wheat

The effects of elevated temperature and CO2 concentration on spot blotch disease of wheat (caused by Cochliobolus sativus) were studied in controlled conditions. Wheat plants were grown in phytotron chambers in two levels of temperatures (22 and 25°C) and CO2 concentrations (360 and 550 ppm) and artificially inoculated with spores of pathogen at 30 days old. Influence of elevated CO2 was noted in terms of increased leaf area, spot size, percentage of leaf necrotic area and decrease in spot numbers cm-2 of leaf, incubation period and latent period. Temperature rise increased spot number and necrotic area of leaves and decreased incubation and latent period but did not affect mean size of spots as well as leaf area. By increasing both CO2 and temperature levels, significant decrease in incubation and latent period and increase in percentage of leaf infection was noted. The maximum percentage of infection and the shortest duration of incubation and latent period were observed in 550 ppm CO2 and 25°C. The effect of temperature rise under temperature gradient chambers was also observed as significant increase in disease severity in all wheat genotypes and varieties studied. Therefore, CO2þand temperature rise likely to contribute definitive increase in spot blotch severity in wheat.