P. atlantica subsp. kurdica, with the local name of Baneh, is a medicinal plant which grows wild in the Kurdistan province of Iran. The identification of resistance gene analogs holds great promise for development of resistant cultivars. A PCR approach with degenerate primers designed based on conserved NBS-LRR (nucleotide binding site-leucine rich repeat) regions of known disease-resistance (R) genes was used to amplify and clone homologous sequences from P. atlantica subsp. kurdica. A DNA fragment of the expected 500-bp size was amplified. The nucleotide sequence of this amplicon was obtained through sequencing; its predicted amino acid sequence compared to the amino acid sequences of known R-genes revealed significant sequence similarity. Alignment of deduced amino acid sequence of P. atlantica subsp. kurdica resistance gene analog (RGA) showed strong identity, ranging from 68 to 77%, to non-toll interleukin receptor (non-TIR) R-gene subfamily from other plants. A P-loop motif (GMMGGEGKTT), conserved and hydrophobic motif GLPLAL, kinase-2a motif (LLVLDDV), where it was replaced by IAVFDDI and kinase-3a (FGPGSRIII) were presented in all RGA. A phylogenetic tree, based on the deduced amino-acid sequences of PAKRGA1 and RGAs from different species indicated that they were separated in two clusters, which PAKRGA1 was on cluster II. The NBS analogs that we isolated can be used as guidelines to eventually isolate numerous R-genes in Pistachio.
