The Rx gene derived USDA 41956 and Rx1 gene derived CPC 1673 confer equal resistance to the migration of Potato virus X from potato leaves to tubers

Abstract

Genes conferring resistance to Potato virus X (PVX) are known, but it remains unknown whether these genes also confer resistance to the migration of PVX from potato leaves to tubers. Potato leaves of 43 cultivars and breeding lines were inoculated with PVXo and PVXb strains and their subsequent appearance in tubers was assessed. Then, a sequence-characterized amplified region (SCAR) marker was developed, and the nucleotide sequence of the SCAR marker was compared with the sequences of known PVX resistance genes. Eleven cultivars and breeding lines exhibited resistance to viral migration from leaves to tubers. The SCAR marker was detected in all 11 potato cultivars and breeding lines that exhibited resistance to both PVXo and PVXb migration, as well as an additional six lines that had not been screened. Comparisons of the nucleotide sequences of the SCAR markers from Atlantic, Multa, Saco, and USDA 41956 revealed a sequence similarity of 100% with Rx1 resistance gene derived from Solanum tuberosum ssp. andigena CPC 1673 for all cultivars and breeding lines and a sequence similarity of 99.5% with the Rx2 resistance gene derived from Solanum acaule. The Rx gene was inherited as immune resistance by a single dominant gene. Within the SCAR marker, Rx had a higher sequence similarity with Rx1 than with Rx2 and it was suggested that Rx and Rx1 are the same gene derived from the S. tuberosum ssp. andigena. Introducing Rx or Rx1 into cultivars to obtain PVX free potato tubers is effective in potato breeding.