Impact of elevated atmospheric CO2 level on powdery mildew (Blumeria graminis f.sp tritici) severity in wheat depends on the pathotype x genotype interaction

Disease resistance is influenced by a variety of environmental factors. The rise in the atmospheric CO2 level affects plant metabolism, physiology and development; which has an impact on pathogen invasion and the disease progress. The aim of the present work was to investigate the effect of CO2 enrichment on powdery mildew (PM) infection in winter wheat. Disease severity caused by two PM pathotypes was studied in Conviron PGV-36 growth chambers at ambient (390 ppm) and elevated (750 pm) CO2 levels on seven varieties with different levels of resistance. Elevated CO2 (EC) resulted in more severe PM infection by pathotype R51 in most genotypes (Bezosztaja 1, Ukrainka, Libellula, Mv Mambo, Mv Emma), compared to ambient CO2, while pathotype R76 caused similar or lower infection level depending on the genotype. The two pathotypes, however, affected Ukrainka in a different way, as R51 resulted in higher while R76 in less severe infection due to elevated CO2. In the case of Apache, neither pathotype caused any change in PM severity in response to EC. The resistant variety, Mv Regiment, remained resistant to either R51 or R76 even at EC. During the progress of PM infection, the stomatal conductance of infected wheat leaves increased in general, at both CO2 levels. Despite the fact that R51 has the most virulence factors (infecting all of the 8 wheat genotypes used in the Nover differential set for identification of PM pathotypes while R76 infects 7; Frauenstein et al. 1979), R76 usually caused more severe initial disease symptoms than R51 at ambient CO2 level. In three varieties (Bezosztaja 1, Ukrainka, Libellula), however, R51 lead to the most severe final infection level. These findings underline the importance of resistance traits against diseases in a future environment with elevated atmospheric CO2 levels. (C) 2015 The Authors. Published by Elsevier B.V.