1a. Objectives (from AD-416)
Improve levels of disease resistance to foliar and soil-borne pathogens in potatoes. Improve processing and nutritional quality in potatoes through breeding and selection of superior germplasm. Evaluate advanced selections through replicated field trials prior to naming and release to stakeholders.
1b. Approach (from AD-416)
Use recurrent selection to improve diploid populations for disease resistances and processing quality. Use parental line breeding to improve tetraploid populations for disease resistances, processing quality, and nutritional quality. Transfer these traits from improved diploids to the tetraploid level via 4x-2x crosses. Develop markers to facilitate introgression of desirable genes or deletion of undesirable genes from related species into commercial germplasm.
3. Progress Report
Crosses (4x-2x) were made between tetraploid red-skinned varieties and diploid potatoes from the cycle two populations with resistance to early blight or late blight. Crosses at the tetraploid level were made to combine chipping ability and resistance to late blight and potato virus Y. Late blight resistance from the diploid cycle one late blight resistant population was successfully incorporated into tetraploid potato germplasm: two of the nine 4x-2x potato hybrids were highly resistant to late blight. Potato variety collections were screened for resistance to early blight and dry rot. Segregating families were screened for resistance to late blight and common scab. Heritabilities for tuber mineral content (boron, calcium, copper, iron, phosphorus, potassium, magnesium, manganese, sulfur, and zinc) revealed that sufficient genetic variation exists to make breeding for improved mineral content feasible. Yellow-fleshed clones from three families were characterized for carotenoid profiles and quantities. Clones with more carotenoids than available in commercial varieties were identified. Second year field generation germplasm was distributed to six sites for evaluation and selection. In general, ½ of the selections were discarded by the breeder and the other location, ¼ were saved by the breeder but not selected at the other location, 1/8 were saved by both the breeder and the other location, and 1/8 were discarded by the breeder but saved at the other location.
1. Reaction of potatoes to common scab is inconsistent across the U.S. Common scab, caused by several Streptomyces species, is a serious soil-borne disease that affects potato tubers. Little is known about the genetic nature of resistance to common scab, nor about how different growing environments and variable Streptomyces species composition at different locations may affect symptom expression. Varieties bred for resistance at one location may not be resistant at another location which makes breeding scab resistant varieties difficult. In order to more adequately evaluate breeding selections for resistance to common scab and identify selections that are resistant to common scab under a wide range of conditions, advanced potato selections from public breeding programs were evaluated for the type of lesion produced (superficial, raised, or pitted), the amount of the tuber surface showing symptoms, and the percentage of tubers infected at three locations (Maine, Minnesota, and Idaho) for six years. Type of lesion was the most informative factor for discriminating among clones and had the largest genetic component of resistance. None of the clones had consistent symptom expressions among locations over the years. This research demonstrates the importance of evaluating advanced selections for resistance to common scab in multiple environments prior to their release to the growing community and has enabled breeders to characterize newly released varieties for their reaction to Streptomyces.
5. Significant Activities that Support Special Target Populations
Seed of ‘Peter Wilcox’, a purple-skinned, yellow-fleshed potato variety which was officially released in 2007, was distributed to organic and road-side market growers.
Haynes, K.G., Christ, B.J., Vinyard, B.T. 2008. Determining the Importance of Combining Ability for Late Blight Resistance in Early Generations of Potato Breeding When Susceptible Clones are Discarded. American Journal of Potato Research. 85:445-454.
Wickramasinge, W., Qu, S., Costanzo, S., Haynes, K.G., Christ, B. 2009. Development of PCR-Based Markers Linked to Quantitative Resistance to Late Blight in a Diploid Hybrid Potato Population of Solanum phureja × S. stenotomum. American Journal of Potato Research. 86:188-195.