Development of a triplex (YYYy) parental potato line with extreme resistance to potato virus Y using marker assisted selection

Abstract

SummaryThe present study was undertaken to validate a sequence characterised amplified region (SCAR) marker tightlylinked to the potato virus Y (PVY) resistant gene (Ryadg) and its further use to develop a triplex parental line using marker assisted selection (MAS). The expected SCAR marker was detected in 11 PVY-resistant genotypes, including putative duplex clones, and was absent in PVY-susceptible genotypes. The resistant genotypes were also screened by double-anitbody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and the results agreed with the SCAR marker data. Based on having a high marker band intensity, three putative duplex clones (YY-3, YY-6, and YY-13) were selected and were inter-crossed to ascertain their duplex status. Based on the PVY resistant (R): PVY susceptible (S) segregation ratio of their three respective progenies, the three clones were confirmed to be duplex clones. Similarly, five putative triplex clones were selected from the segregating progenies of two diploid clones based on having a higher marker band intensity. These were test-crossed with PVY-susceptible, nulliplex clones. The expected segregation ratio (27:1) following random chromatid assortment was tested for in the progenies. The triplex clone, YY-6/3 C11 was identified as carrying the extreme resistance gene to PVY. Use of this elite parental line in potato breeding programmes would ensure that 96% of the progeny carried at least one copy of the Ryadg gene, thus having extreme resistance to PVY. This would eliminate the need to screen using DAS-ELISA and would also reduce the widespread degeneration of potato seed by reducing the incidence of co-infections in which PVY is more damaging with Potato Virus X (PVX) and/or Potato Leaf Roll Virus (PLRV) on the sub-tropical plains of India where approx. 90% of potatoes are grown.This study showed that MAS can be used to speed-up a conventional breeding programme to develop a desired genotype.