Disease resistance protein. Resistance proteins guard the plant against pathogens that contain an appropriate avirulence protein via a direct or indirect interaction with this avirulence protein. That triggers a defense system which restricts the pathogen growth. Confers a broad resistance to all known races of P.infestans. Constitutively expressed. Can be introduced into cultivated potato (S.tuberosum) or tomato (L.esculentum) to transfer a broad-spectrum late blight resistance to cultivated Solanaceae from sexually incompatible host species. Belongs to a four-gene family located at the same locus. Although the four genes are expressed in the resistant haplotype, only RGA2 confers the resistance to P.infestans. In the susceptible haplotype, RGA1 and RGA3 are likely to be pseudogenes created by deletions and mutations, while RGA2 contains also several modifications. Belongs to the disease resistance NB-LRR family.