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IntroductionApple scab is a major problem in both Turkish and global apple markets. This disease is responsible for a decrease in the total market value of the fruit by 70%, resulting in production losses ranging from 30% to 60% (Türkoğlu, 1978;Agrios, 1997). On average, apple producers in Turkey apply fungicides 20-30 times per season in order to control the incidence of the causal pathogen, Venturia inaequalis, which is attributed to excess environmental pollutants (Boyraz et al., 2005;Soriano et al., 2009).V. inaequalis has a high degree of genetic variability due to recombination, thus leading to selective pressures on the fungal pathogen to overcome host resistance. An example of this selective pressure leading to host plant susceptibility was observed in Golden Delicious apple varieties. During the 1900s, Golden Delicious apples were highly resistant to apple scab, whereas today this variety is considered one of the most susceptible apple varieties (Gessler et al., 2006).