Evaluation of Resistance Level of Some Selected Local Apple Genotypes to Fire Blight Disease

Fire blight disease caused by Erwinia amylovora is one of the most important diseases of pome fruits worldwide. In this research, the resistance of 24 selected apple genotypes was evaluated using a mixture of four Erwinia amylovora strains collected from Alborz, Kordestan, West Azarbijan and Khorassan Razavi. The plant material was grafted on apple seedlings in 2013. The grafted plants were transferred to the greenhouse and evaluated for fire blight resistance in spring 2015 and 2016- using shoot-tip inoculation method. Five weeks after inoculation, the blight severity were scored and recorded based on the progression of necrotic area on shoots. Based on the results, the fire blight severity was higher in 2015 than 2016 (24.54% and 17.68%, respectively). The results also indicated that seedling (SSB) and Shemirani Tabestaneh (SH2) genotypes were susceptible and three genotypes including Bigi Kenar Roundkhameh (B-K-Kh), Torbati (T-R1) and Kouzehei Salmasi (Go-Sa) were resistant. Genotypes were grouped into four classes including; susceptible (4.35%), moderately susceptible (13.04%), moderately resistant (17.39%) and resistant (65.52%), and there was no highly susceptible genotype. The results showed that most of the local apple genotypes examined in this research were resistant to fibre blight disease.