Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2008
Publication Date: 8/1/2009
Citation: Whitworth, J.L., Novy, R.G., Hall, D.G., Crosslin, J., Brown, C.R. 2009. Characterization of broad spectrum Potato virus Y resistance in a Solanum tuberosum ssp. andigena-derived population and select breeding clones using molecular markers, grafting, and field inoculations. American Journal of Potato Research. 86:286-296. Interpretive Summary: Potato virus Y (PVY) causes yield loss in potato. New PVY necrotic strains designated as PVYNTN and PVYN:O have been shown to cause tuber necrosis resulting in quality loss. Use of PVY resistant cultivars is an effective control measure, but resistance should be effective against all strains of PVY. Extreme resistance is defined as resistance against all strains. A resistance gene provided by Solanum tuberosum ssp. andigena designated as Ryadg has been shown to confer resistance against PVYO, PVYN, and PVYNTN strains, but it has not been tested against PVYN:O, a newly detected strain in North America. Molecular markers for Ryadg have been developed and successfully used to identify clones with this R-gene. In this study, three of these markers were used to screen a breeding population derived from a resistant x susceptible cross, with the resistant parent contributing the Ryadg gene. The population was inoculated with multiple isolates of PVYO, PVYNTN, and PVYN:O. Results from the breeding population test showed that the presence of markers coincides with PVY resistance against all PVY strains in N. America. In addition, a collection of 53 clones with diverse background were tested with these markers to determine which clones carry the R-gene. Results from the breeding clones also showed agreement between marker presence and PVY resistance obtained from field and/or greenhouse inoculations. These markers can then be used to screen for PVY resistance against all strains and clones characterized for this resistance can be used in breeding programs to increase the number of PVY resistant progeny.
Technical Abstract: Potato virus Y causes yield loss in potato and PVY necrotic strains can result in loss of quality due to tissue necrosis in infected tubers The Ryadg gene from Solanum tuberosum ssp. andigena has been shown to provide resistance PVYO and PVYN/NTN strains and is useful in breeding for resistance to this virus. Extreme resistance has been defined as resistance against all strains, however, clones with the Ryadg gene have not been screened against PVYN:O, a newly detected recombinant strain in North America. This work examined the usefulness of three molecular markers for detecting Ryadg in tetraploid progeny of a cross between R247-1 (PVY resistant) x GemStar Russet (PVY susceptible) as well as selected breeding clones/cultivars from the USDA-ARS Aberdeen, Idaho potato breeding program. Multiple PVY strains and isolates (three PVYNTN, three PVYN:O, and two PVYO) were used for mechanical inoculations of the segregating population and two PVY strains were used for inoculation by grafting. Progeny segregated 1:1 for resistance to PVY, most closely fitting a gene model whereby R247-1 was simplex for Ryadg. Progeny of R247-1 with the presence of all three markers diagnostic for Ryadg were resistant to all PVY strains, including PVYN:O. Molecular markers associated with the presence of Ryadg were also in agreement with a resistant reaction in a concurrent survey of breeding clones/cultivars. The findings of this study support the utilization of the Ryadg-diagnostic molecular markers in a breeding program for the identification of individuals with extreme resistance to all strains of PVY present in North America.