Most plant qualitative resistances are controlled by R genes that encode proteins with nucleotide-binding site (NBS), leucine-rich repeat (LRR), coiled-coil (CC) structure, transmembrane domain (TM) or protein kinase domain (PK).The plant genomes carry a large number of genes encoding proteins with such structures, called resistance gene analog (RGA), but most of them have not been characterized and their functions are still not known.