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Abstract
A resistance gene analog (RGA)-derived sequence-characterized amplified region (SCAR) marker was successfully developed based on sequence homology with disease resistance genes of an AFLP molecular marker tightly linked to the Rl ^sub adg^ gene of Solanum tuberosum ssp. andigena. The new marker was designated as 'RGASC850' (RGA-derived SCAR) based on the size of the amplified fragment. 'RGASC850' could be efficiently used for monitoring introgression of Rl ^sub adg^ against backgrounds of improved gene pools with low likelihood of identifying false positives due to recombination. This SCAR proved to be highly predictive of Rl ^sub adg^-based resistance, as it did not amplify potato leafroll virus (PLRV) resistance sources other than andigena, and thus would be useful in developing cultivars with complementary sources of resistance to PLRV. In addition, a cleaved amplified polymorphic sequence (CAPS) marker based on 'RGASC850' was developed capable of distinguishing genotypes carrying Rl ^sub adg^. This CAPS marker would be useful for screening breeding populations derived from wide crosses, and confirming presence of the Rl ^sub adg^ gene in those parents amplifying the 'RGASC850' marker.