Abstract

DNA markers are increasingly used in potato breeding for resistance to late blight. Such markers are generally based on polymerase chain reaction amplification of sequences of resistance genes introduced into cultivated potato varieties from wild tuber-bearing Solanum species. However, if nonfunctional homologues of resistance genes are being revealed with DNA markers, there will be no association between plant resistance and the occurrence/ absence of these markers. In order to increase the reliability of such DNA markers, it would be desirable to test the functionality of the genetic targets used to develop these markers. It makes sense to begin testing functionality by assessing the expression of these genetic targets, because the absence of expression will clearly indicate the absence of function, and this, in turn, will make it possible to immediately reject markers of inactive homologues of resistance (R) genes. The present study is dedicated to the examination of expression of 10 R genes: R1, R2, Rpi-blb3, R3a, R3b, Rpi-blb1, Rpi-sto1, Rpi-blb2, Rpi-vnt1.3, and Rpi-chc1, detected using 11 sequence-characterized amplified region markers of these genes in wild Solanum species and potato cultivars. As a result of this study, most markers were shown to be associated with expressed R genes, and these markers can be recommended for further use in marker-assisted selection for resistance to late blight. On the other hand, the revealed homologues of the R3a and Rpi-blb2 genes seem to be inactive outside the species in which these genes were originally discovered, and the Rpi-sto1 gene has both expressed and non-expressed variants.

Key words: DNA markers, potato, late blight disease, resistance genes, expression