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:
Internal heat necrosis is a severe physiological disorder in potato tubers that occurs under high temperature growing conditions and is characterized by brown necrotic tissue in the tuber parenchyma. In 2012 we released a new chipping variety with resistance to internal heat necrosis, Elkton. Elkton is adapted to the southeastern U.S. Trials in the south-central and south-western U.S. are in progress. Plant variety protection has been applied for Elkton. The variety has been licensed to a certified seed producer. Late blight disease occurs worldwide and is one of the most important diseases to affect potatoes. Under conditions favorable to the pathogen, late blight can completely destroy a crop in as little as 7-10 days if the crop is not protected, and growers will have to apply fungicides every 5-7 days for control. Using recurrent selection, a late blight resistant diploid potato population was developed: the amount of foliar late blight in the population was reduced by 2/3 after the second cycle of selection. Studies are underway to transfer this resistance into commercial quality potatoes. If successful, growers will be able to apply less pesticides during the growing season. Potato breeders typically evaluate up to 100,000 seedlings each year, make selections, and continue to evaluate these selections for another 2-3 years before sending seed of them elsewhere for evaluation, by which time less than 1% of the original population has been retained. We sent seed of all of our second-year field generation materials to five eastern state collaborators for evaluation. In the three years of this study, we found that 30–70% of the clones which were selected by multiple state collaborators had not been selected at the breeding location and represented potentially new, broadly adapted varieties that had not been identified before they would have normally been discarded. In light of this, our selection strategy has been modified to favor early generation selection. This should hasten the development of widely-adapted varieties. Carotenoids have many human health benefits. Yellow-flesh potatoes are higher in carotenoid content than white-flesh potatoes. The two carotenoids of most interest in potatoes are lutein and zeaxanthin, which play a role in preventing macular degeneration, the most common form of blindness in the elderly. We identified high, moderate, and low carotenoid diploid potatoes and using 2n pollen, crossed them to the same yellow-fleshed tetraploid parent. High, intermediate, and low carotenoid tetraploid progeny were found in each family; the highest carotenoid progeny had a 2- to 3-fold increase in carotenoid content as compared to the tetraploid parent. Based on segregation ratios of white-flesh to yellow-flesh progeny, we found that 2n pollen in the diploid parents was produced by a second division restitution mechanism. This information will be useful in our efforts to enhance the nutritional content of future varieties.
1. Two cycles of recurrent maternal half-sib family selection decreased the amount of foliar late blight in a diploid S. phureja-S. stentomum population by 2/3. Successful crosses between S. tuberosum and late blight resistant diploids from this population were made to transfer this resistance into the commercial germplasm base. Mini-tubers from random matings within this population were produced and sent to Mexico where complex races of Phytohphthora infestans, the causal organism of late blight disease, occur in order to test the durability of resistance in this population.
Haynes, K.G., Gergela, D.M., Hutchinson, C.M., Yencho, G.C., Clough, Henninger, M.R., Halseth, D.E., Sandsted, E., Porter, G.A., Ocaya, P.C. 2012. Early Generation Selection at Multiple Locations may Identify Potato Parents that produce more widely adapted Progency. Euphytica. 186:573-583.