Analysis of the applicability of molecular markers linked to the PVY extreme resistance gene Rysto, and the identification of new markers.

In this study molecular markers linked to the Rysto gene, which originates from the wild potato species Solanum stoloniferum and confers extreme resistance against PVY, were identified and the applicability of recently published Rysto, markers was analyzed. Three RAPD markers covering a total distance of 8.60 cM were detected in this experiment. The closest of these markers was located 0.53 cM from the gene. From among the published markers only one had diagnostic value in the experimental plant material, and mapped 2.95 cM from the gene, on the side opposite the RAPD markers developed in the present study. All the markers analyzed were present in Solanum stoloniferum accessions, irrespective of their resistance, indicating that these sequences are linked to the locus and not exclusively to the dominant allele of the Rysto gene in the wild species. The inapplicability of several published markers indicates that the genetic background is decisive in this tetraploid and highly heterozygous species. This means that it may be necessary to develop markers from the breeding material itself, until the resistance gene is not cloned and cannot be used as a selection marker in marker-assisted selection.