Effects of Ozone Exposure on Resistance of Wheat Genotypes to Pyrenophora tritici-repentis

Abstract

Three spring wheat genotypes, susceptible, moderately resistant or resistant to Pyrenophora tritici‐repentis (tan spot fungus) were exposed to charcoal‐filtered air and to approx. 80, 160, 240 (g m−3 ozone for five consecutive days (7 h per day). Visible leaf injury on seedling plants (three‐leaf stage) was only observed after fumigation with 160 or 240 (g m−3 O3. Amount of injury was four‐fold and 10‐fold on the susceptible genotype when compared to resistant or moderately resistant genotype at the two highest concentration of ozone, respectively. Genotypic differences to O3 tolerance were detected at the seedling growth stage (three‐leaf stage) and flowering stage but not at the stem elongation stage. A significant increase in tan spot lesion area was observed only on O3 predisposed second top most leaves of the susceptible genotype at all the three levels of ozone. Predisposition did not enhance tan spot development in resistant and moderately resistant genotypes. In a test with 12 wheat genotypes, a highly significant positive correlation (r = 0· 986, p < 0· 0001) was observed between ozone sensitivity (percent leaf area damaged due to 240 (g m−3 ozone exposure) and tan spot development (mm2 lesion area) following inoculation with P. tritici‐repentis. It indicates that wheat genotypes resistant to the tan spot fungus might be tolerant to ozone damage.