2011 Annual Report 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, 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 Breeding for potato tuber quality and disease resistance. Our potato breeding program is actively breeding for improved chipping quality, nutritive value and disease resistance. This effort involves use of adapted tetraploid potato and exotic diploid and wild accessions. Incremental progress is achieved with each breeding cycle wherein crosses between plants with promising attributes are made to combine desirable attributes into single plants. This past year, crosses were made among advanced tetraploid selections to combine improved chipping potential and resistance to late blight and potato virus Y. Promising individuals will be identified in field evaluations. Bulk pollinations among late blight resistant diploid populations were also made to advance the populations for spring testing in the field. Crosses among yellow-fleshed clones with high carotenoid levels were made in the summer to generate segregating populations that will be used to elucidate the allelic composition of yellow-fleshed parents at the beta-carotene hydroxylase locus. A tetraploid population previously characterized for resistance to internal heat necrosis, chipping ability, and specific gravity was distributed to three state cooperators for characterization of common scab resistance. Superior clones will be selected for advancement in the breeding program. SSR molecular markers were developed for the latter population with collaborators to begin research to identify markers linked to disease and quality related genes. Wild species at the hexaploid, tetraploid, and diploid level were screened in tissue culture for root biomass to identify species for use in breeding for nitrogen uptake efficiency. Late blight resistant and orange-fleshed diploid potatoes were screened for 2n pollen in order to begin introgressing this material into adapted tetraploid breeding lines. 4.Accomplishments 1. Potato tuber carotenoid content. Carotenoids, which impart yellow color to the flesh of potato tubers, have many important human health benefits. We are developing nutritionally improved cultivars. Very high carotenoid germplasm was identified in exotic diploid potato (cultivated potato is tetraploid) but no information was available as to how readily carotenoid content in tetraploid germplasm could be improved using these diploids. Three diploids, with carotenoid concentrations 13 times greater, 6 times greater, and less than ‘Yukon Gold’ (currently the most popular yellow-flesh variety in the U.S.) were crossed to the same light-yellow-fleshed parent. By examining the progeny from these crosses, we determined that genetic variation for carotenoid content occurred within families but not between families. There were no significant differences among these three families for carotenoid content. High, intermediate, and low carotenoid progeny were found within all three families. As long as one of the parents is yellow-fleshed, progeny will segregate for carotenoid content and yellow-flesh and suitable high carotenoid parents can be selected for breeding. The results of this genetic study will be valuable for scientists in breeding high carotenoid potatoes with improved nutritive value. 2. Early generation selection in potato breeding. The ARS Potato Breeding Program develops new potato cultivars for the eastern U.S. in close cooperation with scientists at numerous state universities. In the past, selection for superior lines by the ARS program has taken place in northern Maine for three years before seed is distributed elsewhere for evaluation and selection of superior clones at cooperator locations. After three years of selection in Maine under the conventional ARS breeding scheme, only 1% of the original population remains for distribution to cooperators. In order to broaden the diversity of material available for evaluation by cooperators at different locations, we began distributing seed to cooperators a year earlier. In three years of testing clones distributed by ARS a year earlier from the breeding program, 27-70% of the progeny selected for superior attributes by cooperators at half or more of the cooperator locations had not been selected by the ARS breeding program and hence would not normally have been available to cooperators under our normal breeding practice. Our new early-generation distribution strategy allows greater opportunity to identify potato parents that produce widely-adapted progeny and retention of this material for breeding widely adapted cultivars. As a result of this study, the ARS breeding strategy is being modified in favor of early generation selection. These results will benefit scientists breeding improved potato cultivars for eastern U.S. production. Review Publications Brown, C.R., Haynes, K.G., Moore, M., Pavek, M.J., Hane, D.C., Love, S.L., Novy, R.G., Miller, Jr, J.C. 2010. Stability and Broad-sense Heritability of Mineral Content in Potato: Iron. American Journal of Potato Research. 87: 390–396. Nitzan, N., Haynes, K.G., Miller, J., Johnson, D., Cummings, T., Batchelor, D., Olsen, C., Brown, C.R. 2011. Genetic Stability in Potato Germplasm for Resistance to Root Galling Caused by the Powdery Scab Pathogen Spongospora subterranea. American Journal of Potato Research. 87:497-501. Mccord, P.H., Sosinski, B.R., Haynes, K.G., Clough, M.E., Yencho, G.C. 2010. QTL mapping of internal heat necrosis in tetraploid potato. Theoretical and Applied Genetics. 122:129-142. Brown, C.R., Haynes, K.G., Moore, M., Pavek, M., Hane, D., Love, S., Novy, R.G., Miller, J.C. 2011. Stability and Broad-sense Heritability of Mineral Content in Potato: Zinc. American Journal of Potato Research. 88:238-241. Mccord, P.H., Sosinski, B.R., Haynes, K.G., Clough, M.E., Yencho, G.C. 2010. Linkage mapping and QTL analysis of agronomic traits in tetraploid potato (Solanum tuberosum subsp. tuberosum). Crop Science. 51:771-785. Bradeen, J.M., Haynes, K.G. 2011. Introduction to Potato. In: Bradeen, J.J., Haynes, K.G., editors. Genetics, Genomics and Breeding of Potatoes. Enfield, NH: Science Publishers. p. 300.