ARS | Publication request: Validation and Implementation of Marker-Assisted Selection (MAS) for PVY Resistance (Ryadg gene) in a Tetraploid Potato Breeding Program

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 4, 2009
Publication Date: March 1, 2009
Citation: Ottoman, R.J., Hane, D.C., Brown, C.R., Yilma, S., James, S.R., Mosley, A.R., Crosslin, J., Vales, M.I. 2009. Validation and Implementation of Marker-Assisted Selection (MAS) for PVY Resistance (Ryadg gene) in a Tetraploid Potato Breeding Program. American Journal of Potato Research. 86:304-314.

Interpretive Summary: Potato germplasm requries the use of sources of resistance to pests and diseases in order to breed varieties that are cheaper to grow. Potatoes contract many different viruses. One of the worst is Potato virus Y (PVY) which can reduce yield up to 80 percent. Also, if the virus is relatively symptomless, it can prevent certification of seed, that appeared to be healthy, devastating the seed grower with an unexpected loss of livelihood. There are useful genes that encode resistance to PVY. Although we do not have an actual copy of the genes, we can identify DNA markers located close to the genes which can be revealed by a simple biochemical procedure. Using this procedure the researchers were able to predict accurately the resistance status of early generation breeding materials 96 % of the time. The use of the marker reduces time, expense, and unrealiability of determining which breeding materials are resistant to PVY, thus accelerating the breeding process. Incorporating PVY resistance into a new variety of potato could reduce the more than 100 million dollars that are spent in the Pacific Northwest alone to control viruses. A PVY resistant variety would be easier to grow especially during the seed multiplication process. The only way to stop the ravages of the present ongoing PVY epidemic is through strong genetic resistance

Technical Abstract: The gene Ryadg from S. tuberosum ssp. andigena provides extreme resistance to PVY. This gene has been mapped to chromosome XI and linked PCR-based DNA markers have been identified. Advanced tetraploid russeted potato clones developed by the U.S. Pacific Northwest Potato Breeding Program with Ryadg PVY resistance were used in this study. The objective of this work was to assess the usefulness of molecular markers linked to Ryadg as an indirect tool for selecting PVY resistance in an active tetraploid breeding program. To achieve this, a full-sib tetraploid population segregating for Ryadg was screened with molecular markers linked to Ryadg, artificially inoculated with PVY and evaluated in the greenhouse. A large percentage (96%) of the segregating lines showed coincidence between molecular markers and ELISA results at 40 days after inoculation. The coincidence level was high enough to consider molecular markers as an alternative to artificial inoculation followed by ELISA. Segregation of the ELISA and molecular marker results in the full-sib population indicated the presence of Ryadg as a simplex in OR00003-1. Additional full-sib populations segregating for the Ryadg gene coming from OR00003-1 and from a related clone, OrayT-9, were evaluated under field conditions. Thirty-eight percent of the lines selected at the single hill stage contained markers associated with the PVY resistance gene Ryadg. The practical application was shown using a limited number of clones, but can be extended to much larger populations. We believe that MAS can be used as a fast and efficient tool to select for PVY resistance, reducing the number of PVY susceptible lines retained for succeeding field evaluations, and thereby increasing the odds of generating PVY resistant potato varieties.