Use ofresistancecultivars is one of the major approaches to reduce crop damages caused by biotic stresses. Development of such cultivars requires identification, isolation and mapping ofresistance genes. Plants utilize a variety of strategies to withstand attack by the huge assortment of pathogens found in their habitats. The existence of resistance genes (R-genes) that are able to detect the presence of specific pathogen races by recognizing ligands encoded by the so-called avirulence genes (Avr) of pathogens is one of the most effective and predominant strategies. The nucleotide sequence of the cloned resistance genes from plants indicate that there is conserved regions in these genes is called resistance gene analogues (RGAs). Degenerate primers were designed based on the sequences of RGA and were used in study of resistance mechanism. Among these, the -LRR Keywords : apple, pear, RGA, resistance genes, -LRR
