Association of oxidative stress components with resistance to flax powdery mildew

Abstract

Field trials were conducted in 2008/2009 and 2009/2010 growing seasons at Giza Agricultural Research Station to evaluate powdery mildew (PM) severity on nine flax cultivars. Tested cultivars could be classified into five distinct groups, i.e., highly susceptible (Corland and C.I. 2008), susceptible (Giza 7 and Marshall), moderately susceptible (Cass), moderately resistant (Dakota, Koto and Wilden) and resistant (Ottowa 770B). They showed considerable variation in PM severity ranging from 8.1 on Ottowa 770B to 97.0% infected leaves/plant on Cortland. Total soluble proteins, total phenols, peroxidase, polyphenoloxidase, ascorbic acid, tocopherol and malondialdehyde were determined in infected leaves of the tested cultivars. Pearson's correlation coefficient was calculated to measure the degree of association between PM severity and each biochemical component. All components showed significant (P<0.05) or highly significant (P<0.01) negative correlation with PM severity except MDA, which showed positive correlation (P<0.01). The results of the present study suggest that phenols and MDA in infected leaves could be used to assist the screening of resistant plants at early stages of powdery mildew development.