Reliability of Shoot-Tip-Inocultaion Method and Relative Resistance to Fireblight in some Cultivars and Genotypes of Apple

Fireblight disease caused by Erwinia amylovora is a serious disease of apples worldwide. In this research, resistance of 30 apple superior local genotypes and introduced cultivars was evaluated to fire blight using shoot-tip-inoculation method in glasshouse condition. Repeatability of the inocultion method was also investigated by repeating the experiments for two years (2012 and 2013). The inoculum comprised of four E. amylovora strains including EO1, E4, En and Ek originated from Kordestan, Alborz, Khorasan Razavi and West Azarbijan provinces. Based on the results, different cultivars and genotypes exhibited different resistance level to fire blight disease. In both years, Boshghabi was the most susceptible and Ferdovs and Delicious Mari the most resistant genotypes. Analysis of mean fire blight severity revealed that the first-year data was directly correlated with the second-year (R = 0.54), indicating relative accurence of shoot-tip-inoculation method for fire blight resistance assessment. Collectively, 6.7% of Iranian genotypes were rated as highly susceptible, 46.7% susceptible, 26.7% moderately susceptible, 13% moderately resistant and 6.7% resistant, indicating hight fireblight susceptibility in Iranian apple germplasm.