Isolation of Resistance Gene Analogues (RGAs) in Potato Using Motif directed Profiling Method and Development of Their Genetic Map

Use of resistance cultivars is one of the major approaches to reduce crop damages caused by biotic stresses. Development of such cultivars requires identification, isolation and mapping of resistance genes. In this research, motif directed profiling (MdP) method was used to isolate resistance gene analogues (RGAs) in potato. For this purpose, seven degenerate primers designed based on conserved TIR domain of plant disease resistance genes were used to amplify RGAs in 46 F1 progeny derived from a cross between the diploid heterozygous parents SH83-92-488(SH) and RH89-039-16(RH) with highest recombination. In total, 454 polymorphic markers were produced that were mapped relative to SH×RH linkage map consisted of 10,000 AFLP markers. To identify RGAs, some of the bands were isolated and sequenced and out of which 66.11% (160 bands) represented significant similarity with known resistance genes and RGAs and most of them were mapped in chromosomal regions of potato or tomato having RGA clusters. Linkage map of these RGAs in relation to ultra dense (UHD) genetic map of the population, consisted of 10,000 AFLP markers, showed that most of the RGAs were organized in new or existed clusters or sub-clusters on the map. One hundred and seventeen markers were mapped in the positions corresponding to the resistance gene clusters on chromosomes 5, 6, 9 and 11 and 15 markers were mapped in approximate positions of quantitative resistance loci on chromosomes 1, 2, 4 and 7. The majority of these RGAs represent novel RGA sequences. The results of this research could be used in mapping of single resistance genes and quantitative resistance loci.