Potato virus Y


Potato virus Y (PVY) has long been a major challenge for seed potato production. Infection with PVY can reduce potato yields by over 60% and planting seed potatoes infected with PVY can reduce yields up to 80%.  Major changes have contributed to the re-emergence of PVY as a serious disease threat in the United States in recent years. An important component is the popularity of several russet varieties that escape detection in the field because they show mild or no PVY foliar symptoms while serving as large reservoirs for the virus. In addition, PVY incidence has been exacerbated due to the emergence of a strain that causes tuber necrosis, as well as changes in aphid populations, including the invasion of soybean aphid into the Midwest. 

Genetic resistance remains the best long-term strategy for combating viral diseases of potato. Three sources of natural resistance to PVY exist in potato: Rysto from S. stoloniferum Schlechtd. et Bché, Rychc from S. chacoense Bitt., and Ryadg from S. tuberosum ssp. andigena Hawkes. These three genes are considered different from one another since they map to different locations within their respective genomes. Resistance encoded by the Rysto gene has been incorporated into several cultivars developed through European breeding programs. Cleaved-amplified polymorphic sequence (CAPS) markers derived from the restriction fragment polymorphism loci GP122 were used to detect the Rysto gene in different germplasm sources. PVY resistance from S. chacoense has not been widely utilized in potato breeding although some cultivars with the Rychc gene have been developed. Rychc maps to potato chromosome IX and is located in a region with several NB-LRR genes with nucleotide similarity to the Sw-5 gene conferring resistance to tomato spotted wilt virus in tomato.  

The Rysto and Rychc genes are closely linked to molecular markers that can be used to track them during breeding.  However, identifying and isolating the genes themselves would be beneficial in several ways.  First, a marker within the gene itself would correspond to true resistance more often than a marker that is linked to the gene.  Second, the gene could be isolated and used to introduce directly into susceptible cultivars, making them resistant.  In the long term, having the PVY resistance gene isolated will help us to understand the molecular interactions that take place between the virus and potato gene product and will ultimately help us in identifying resistance genes that can recognize different virus variations (e.g. PVYO, PVYN:O, PVYNTN).

The major short-term outcome of this project will be the identification of genes that can be tracked via molecular markers in parental lines released to breeders.  The longer-range goal is to isolate and clone PVY resistance genes, and then transform potato cultivars to make them resistant to PVY.