|Brown, Charles - Chuck|
|Vales, M. Isabel|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2008
Publication Date: 3/15/2009
Citation: Ottoman, R.J., Hane, D.C., Brown, C.R., Yilma, S., Mosley, A.R., Vales, M. 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. DOI 10.1007/s12230-009-9084-0. Interpretive Summary: The potato crop is subject to diseases like any other crop. A valuable technique for controlling disease is the breeding of varieties resistant to the organism that causes the disorder. Potato Virus Y (PVY) is the most important virus of potato in the US at this time in history. Since potato is propagated vegetatively, once the virus is in potato plants the tubers coming from that plant and the plants that will grow from those tubers will be infected. Seed programs are set up in isolated places to prevent infection by PVY which is transmitted by aphids. Cultivars grown in the Andean Mountains have resistance to PVY controlled by a single gene. This research developed and verified the usefulness of molecular markers for PVY resistance. These markers are small segments of the genetic code that lie extremely close to the actual genes that encode the resistance. The screening process to determine if a genotype is resistant to PVY is extremely time–consuming and expensive. Using the molecular markers it is possible to determine which new genotypes are resistant to PVY with one simple laboratory test. This will accelerate and reduce the cost of breeding new varieties of potato with PVY resistance, and will reduce the overall cost of protecting the potato crop from virus, which is estimated to be $100 million per year in the Pacific Northwest alone.
Technical Abstract: Artificial inoculation under controlled conditions followed by ELISA is traditionally used to screen for PVY resistance. This method is very tedious, time consuming and prohibits screening of large segregating populations. The gene Ry-adg from S. tuberosum ssp. andigena provides extreme resistance to PVY. This gene was mapped to chromosome XI and user-friendly PCR-based DNA markers have been developed. The objective of this work was to assess the usefulness of molecular markers linked to Ry-adg as an indirect selection tool. To achieve this, a full-sib tetraploid population segregating for Ry-adg was screened with molecular markers linked to Ry-adg and artificially inoculated with PVY. Ninety-six percent of the segregating lines showed coincidence between molecular markers and ELISA results at 40 days after inoculations. Discrepancies in 4% of the cases could be caused by escapes from inoculation, errors in ELISA or PCR assays, recombination between the markers and the Ry-adg gene and/or time of evaluation. Segregation of the ELISA and molecular marker results in the full-sib population indicated the presence of Ry-adg as a simplex in the PVY resistant parent. This information was taken into account for screening two segregating populations under field conditions. From 316 clones, nine (2.8%) were selected at the single hill level based on visual tuber characteristics. Four (44.4%) contained markers associated with the PVY resistance gene Ry-adg. By using MAS for PVY resistance we reduced the number of PVY susceptible lines retained for succeeding field evaluations, and thereby increased the odds of generating PVY resistant potato varieties.