MOLECULAR EXAMINATION OF A CHROMOSOME REGION THAT CONTROLS RESISTANCETO POTATO Y-POTYVIRUSES AND A-POTYVIRUSES IN POTATO

The gene R gamma(adg) that confers resistance to potato Y potyvirus (P VY) in the cultivated potato [Solanum tuberosum subsp. andigena, line 2x(v-2)7] is located on chromosome XI in a segment that contains three other known resistance genes in other syntenic solanaceous species. O ne of them is the gene N that controls resistance to tobacco mosaic to bamovirus in tobacco and has previously been isolated and sequenced. T hree sequence-related resistance gene-like (RGL) DNA fragments (354-36 9 bp) highly homologous to the gene N were PCR-amplified from the pota to line 2x(v-2)7. Two RGL fragments (79 and 81% homologous to the N ge ne) co-segregated with R gamma(adg) among the 77 F1 progeny tested. Th ese RGLs may originate from a resistance gene family on chromosome XI. The potato line 2x(v-2)7 also expressed resistance to potato A potyvi rus (PVA), which was controlled by another locus on chromosome XI mapp ed ca. 6.8 cM distal to R gamma(adg).