Location:2008 Annual Report
1a. Objectives (from AD-416)
Objective 1. Identify superior germplasm for potato disease and pest resistance, phytonutrients, minerals and vitamins, using high-throughput methods to determine the extent of natural variation in diverse potato germplasm of select phytonutrients/metabolites. These traits will be incorporated into the cultivated breeding pool using traditional breeding and molecular approaches. Sub-objective 1.A. Identify germplasm with a range of expression of phytonutrients, study inheritance, identify associated markers, and produce superior parents. Sub-objective 1.B. Develop germplasm with resistance to pests and diseases, establishing effective and efficient screening protocols, determining range of expression, inheritance, heritability, and discover molecular markers, while mapping genetic factors where possible and useful. Sub-objective 1.C. Use metabolic profiling of multiple chemical constituents to identify sources of high expression and genotypes possessing desirable combinations. Objective 2. Determine host resistance options, epidemiological parameters and develop diagnostic tests for emerging pests and pathogens of potato. Sub-objective 2.A. Determine the impact, distribution, and importance of the soil-borne viruses tobacco rattle virus (TRV) and potato mop top virus (PMTV) on Pacific Northwest potato production. Assist in evaluating advanced germplasm for resistance to the viruses as materials become available. Sub-objective 2.B. Develop and improve diagnostic procedures for insect transmitted viruses (potato virus Y [PVY] and potato leafroll virus [PLRV]) and phytoplasmas (purple top phytoplasma and aster yellows) in potatoes. Evaluate advanced potato lines for resistance to diverse viruses. Objective 3: Elucidate genetic, molecular and biochemical factors governing host disease resistance and accumulation of select phytonutrients and vitamins. Sub-objective 3.A. Elucidate genetic, molecular and biochemical processes governing accumulation of select phytochemicals and vitamins with respect to improving potato as a food. Sub-objective 3.B. Elucidate genetic, molecular and biochemical processes involved in plant host resistance.
1b. Approach (from AD-416)
Germplasm will be surveyed for expression of disease and pest resistance, and nutraceuticals. High performing genotypes will be intercrossed to with suitable commercial materials to introduce new traits into the potato breeding pool. Inheritance and genomic location will be studied using nucleic acid markers. Transgenics designed to enhance or knock out gene expression will be used to test hypotheses on gene function. Field testing will identify agronomically superior genotypes for use as parents and submission to regional yield trials.
3. Progress Report
Substantial progress has been made on CRIS goals, including in developing potatoes with a higher nutritional value. As a staple food, potatoes are in a unique position to be a valuable source of dietary phytonutrients and vitamins. We found that by manipulating two genes involved in folate biosynthesis that we could obtain potatoes with at least a six-fold higher amount of folate than any existing genotype we have yet identified. We continue to screen diverse germplasm for phenolic phytonutrients and have identified promising genotypes with high phenolic phytonutrient content. Additional germplasm was assessed for total carotenoid, total anthocyanin, hydrophilic Oxygen Radical Absorbance Capacity (H-0RAC) and lipophilic ORAC (L-ORAC). Among these were native cultivars from the center of diversity in the Andes of South America. Considerable variation in total anthocyanins was found and potatoes with solidly red or purple flesh are generally display H-ORACs two to four times higher than white fleshed cultivars. Total carotenoids ranged from 50 to 2600 mcg per 100 g FW. The highest carotenoids were found in progenies of crosses between Papa Amarilla germplasm of South America. Germplasm was examined for mineral content and considerable variation was found in iron, manganese, calcium, phosphorus, potassium contents in advanced breeding lines and varieties. It is likely that iron content in new potato varieties could be increased by 50 percent. In our efforts to improve disease resistance in potatoes, resistance to Columbia root-knot nematode (CRKN) was developed and a selectable marker for root resistance to CRKN identified. Tuber resistance to CRKN and other Root-knot species was identified and determined to be loosely linked to root resistance and to be controlled by a single dominant gene. Resistances to powdery scab, black dot, and corky ringspot disease were identified in breeding materials in both greenhouse and field evaluations. We also have a CRIS component working on emerging diseases. Additional evidence was found that the zebra chip disorder is associated with the presence of potato psyllids (a small insect with piercing-sucking mouth parts). Psyllids may be transmitting a pathogen, but not all psyllid populations cause zebra chip symptoms, suggesting some insects are free of the presumed pathogen that is causing the ZC symptoms. The extensive and characteristic browning that occurs in ZC tubers greatly decreases the marketability of ZC tubers. We used LCMS to characterize changes found in ZC tubers. Major increases were found in several tuber phenolic compounds, especially tyrosine, and this provides insight into the biological mechanisms enabling symptom development. NP 301, Component 3.
1. Analysis of diverse germplasm for carotenoids, anthocyanins and iron. Anthocyanins, carotenoids and iron have health-promoting effects and are desirable/required in the diet. Germplasm was assessed by ARS scientists in the Vegetable and Forrage Crops Production Research Unit in Prosser, WA for total carotenoid, total anthocyanin, and iron. Considerable variation in total anthocyanins was found, while total carotenoids ranged from 50 to 2600 microgram per 100 g FW with the most carotenoids found in progeny of Papa Amarilla from South America. The variation found in iron, suggests that iron content in new potato varieties could be increased by 50 percent. This information will contribute to the development of potatoes with enhanced nutritional value. NP 301 Component 3: Genetic Improvement of Crops. 3c: Germplasm Enhancement/Release of Improved Genetic Resources
5. Significant Activities that Support Special Target Populations
Development of specialty varieties with enhanced culinary traits and nutritional profiles has attracted the interest especially of small producers. The value added element allows them to consider marketing smaller quantities in markets that pay considerably more per pound than the traditional markets. We have identified and collected potatoes that have been grown for hundreds of years by Native Americans and Native Alaskans. We have introduced these cultivars to tissue culture, eradicated viruses and re-intoduced them to the Native groups. This has helped to preserve their place in the industrial ethnobotany of the tribes and increased enthusiasm for science education of their own heritage food item. Every year we take several thousand cuttings of potato to the Makah Nation, and have a Potato Day, with talks about science, nutrition, gardening and politics of food production. In Alaska, "Maria's Potato" was re-introduced to the Tlingit village where it was originally grown years after it had disappeared.
Crosslin, J., Hamm, P.B., Pike, K.S., Mowry, T.M., Nolte, P., Mojtahedi, H. 2007. Managing diseases caused by viruses, viroids, and phytoplasmas. Book Chapter. Pages 161-169 in: Potato Health Management, 2nd ediiton. D.A. Johnson, editor. APS Press.