One of the key developments in plant breeding in the last 20 years has been the use of molecular markers to select for genetic traits in segregating populations. Disease resistance is perhaps the prime example of a trait amenable to marker-assisted selection. Thanks to the diligent work of Grace Christensen (research specialist for the breeding program), we are now able to use genetic markers to track two resistance genes for potato virus Y (PVY). One gene, designated Ry(adg), was introduced to cultivated potato (S. tuberosum ssp. tuberosum) from S. tuberosum ssp. andigena, and the other gene, Ry(sto), was introduced from the wild species S. stoloniferum. The presence of either gene confers extreme resistance to PVY, which is very desirable as PVY is the leading reason why seed potatoes fail certification in Wisconsin.
The markers for both genes can be assayed using PCR and gel electrophoresis. The gel image below shows our result for the Ry(sto) marker known as YES3-3B.
The YES3-3B marker linked to Ry(sto) produces a 284 bp fragment, which is visible as a third band on the left side. To ensure the assay was working, we included W8946-1rus as a positive control, which is known to have inherited Ry(sto) from the USDA-ARS breeding line PA98V1-2. For a negative control we used the PVY-susceptible line W6234-1rus. Of the four new breeding lines tested in this gel, only AW08417-6rus showed a banding pattern indicating the presence of Ry(sto). The other three did not inherit the resistance gene.