Location: Vegetable Crops Research
2024 Annual Report
Objectives
Objective 1: Conduct research to develop genetic resource maintenance, evaluation, or characterization methods and, in alignment with the overall NPGS Plan, apply them to priority potato genetic resources to avoid backlogs in genetic resource and information management.
Objective 2: Acquire, distribute, and maintain the safety, genetic integrity, health, and viability of priority potato genetic resources and associated descriptive information.
Approach
Conduct research to develop genetic resource maintenance, evaluation, or characterization methods and, in alignment with the overall NPGS Plan, apply them to priority potato genetic resources to avoid backlogs in genetic resource and information management. Make core subsets from species with many populations, or complete a related study of status and dynamics of genetic diversity in the genebank. Perform one in-house phenotypic evaluation, ideally for a new valuable trait, or for common traits from a more breeding-friendly germplasm source. Perform joint research projects with specialist collaborators to identify valuable germplasm, including making of custom samples, propagules and/or research populations. Identify in situ population locations and study valuable germplasm at sites in southwest U.S. Perform greenhouse botanical seed multiplication. Annually assess whole seed collection in terms of seed numbers and germination. Process, label, organize, and store multiplied seeds at -20C. Rely on longstanding methods to secure new seeds (at least 200 accessions per year) in storage in a way that results in maximum long-term viability. Transfer in vitro clonal collection stocks to fresh medium as needed to maintain viability. Use longstanding methods to keep the 1500 clonal collection alive and continuously available for distribution. Maintain optimal virus test schedule and records for all seeds and clones. Assess germination of all seedlots within a 5-year interval which equals at least 1200 accessions per year. Distribute data, advice, information, and germplasm efficiently to cooperators.
Progress Report
Objective 1 - Research for characterization and technical use of the germplasm:
1) A second year of tests confirmed the identity of a core collection of adapted diploid cultivated potato lines useful for potato breeders to identify new gene sources with high Late blight resistance.
2) Stocks with novel introgression of large-tuber mutant from Solanum cardiophyllum (cph) were planted for field and greenhouse evaluation. These are very closely-related to the “Four Corners” potato, S. jamesii (jam), cultivated by the ancient Puebloan people in the U.S. Southwest. We want to show that introgression into jam could make this a viable Navajo specialty variety, and test for evidence that cph was intentionally brought from Mexico in prehistoric times to increase yields at habitation sites like Mesa Verde, Chaco Canyon, and Canyon del Chelly.
3) Progress was made in identifying a simple plant constituent chemical that confers strong Colorado potato beetle (CPB) resistance. We used selected plants of the wild diploid potato species S. okadae (oka) to contribute strong CPB leaf feeding resistance, and we hybridized it with CPB-susceptible cultivated diploid potato, making a segregating F2 population. We showed that feeding resistance tracks with levels of cardiac glycosides contributed by oka, and can be very expeditiously assessed with a simple, fast lab test.
4) Progress was made to the 6th generation of backcrossing, validating this approach to preserving rare single-genotype accessions in botanical seed form. Sometimes unique plants with valuable traits are identified and these plants can be propagated clonally by tubers or grown as plantlets in tissue culture, but they must be frequently propagated and are more vulnerable to pathogens and environmental stress than are seeds. To preserve unique plants of S. jamesii we have been backcrossing them six generations to preserve them as botanical seed.
5) Progress was made in synthesizing and testing populations with resistance to Zebra chip disease. With ARS cooperators in Wapato, Washington, we tested selections from nearly 100 populations of S. microdontum (mcd) for Lso, the bacterial cause of Zebra chip disease of potato and we identified two elite mcd clones for further study and breeding. We also have created hybrid families segregating for resistance to identify genes associated with resistance.
6) Eight new populations of S. jamesii were collected in New Mexico. Samples of these plants are available for study.
Objective 2 - Service for maintaining and improving germplasm services for the nation’s researchers and breeders:
1) Progress was made in converting a duplicate set of the clonal tissue culture collection to microtubers. The genebank has over 1,000 clonal germplasm items which are kept in test tube form. Tubers in sterile test tube culture should provide secure backup storage for up to five years. To further protect the germplasm collection, a separate fireproof building is being prepared to secure a second copy of all genebank seed collections in Wisconsin.
2) Polymerase Chain Reaction- based testing for Potato Spindle Tuber Viroid (PSTV) was completed for all germplasm. We modified and validated a PCR (polymerase chain reaction)-based test directly on botanical seeds in the germplasm collection and now have retested all seedlots in the genebank.
3) Field and greenhouse grow-outs confirmed the identities of all multiplied genebank seedlots.
4) This year we produced seed in germplasm that resists seed multiplication by crossing with a highly fertile universal mates. We have been selecting and developing alternate mates that contribute not only fertility, but other useful traits, like self-compatibility, disease resistances, and enhanced field tuberization.
Accomplishments
1. Acquisition of valuable potato breeding stocks that will combat drought, frost and disease. The potato is the most important vegetable crop in the United States and world. Frosts early and late in the season can reduce yield and quality of the crop. Drought stress tolerance can reduce losses if rain becomes less reliable and irrigation more expensive. Natural Late blight and Zebra chip resistance are economical alternatives to pesticide application. ARS researchers at Madison, Wisconsin, and their collaborators, propagated and evaluated a new frost and drought tolerant variety, Wiñay, from Peru. This cultivar resulted from a joint international breeding effort, and how is available in the USA for ongoing frost and drought tolerance research and breeding. They discovered potent resistance to Zebra chip, a very serious disease of potato tubers, in Solanum microdontum. Two elite S. microdontum parents were identified and an F2 family produced. They identified individuals in the wild species Solanum kurtzianum with extreme drought resistance. The nearly 100 populations of this species in the genebank were systematically screened for drought tolerance by multiple methods. Outstanding parents were intermated, and progeny were retested and selected for two more cycles. After final evaluation against standards, a population with concentrated extreme drought tolerance will be released to researchers and breeders. The U.S. Potato Genebank (USPG) has now identified, multiplied, and preserved selections that have extreme value for each of these traits and made them available to clients. Now users of USPG germplasm will have potent new tools to protect it from new diseases; and stresses like heat, drought, disease and frost, all which have increasing importance due to climate change.
Review Publications
Arcos-Pineda, J., del Rio, A., Bamberg, J.B., Vega-Semorile, S., Palta, J., Salas, A., Gomez, R., Roca, W., Ellis, D. 2024. An international breeding project using a wild potato relative Solanum commersonii resulted in two new frost-tolerant native potato cultivars for the Andes and the Altiplano. Frontiers in Plant Science. 15. https://doi.org/10.3389/fpls.2024.1358565.
Bamberg, J.B., Del Rio, A., Kinder, D., Louderback, L., Pavlik, B., Fernandez, C. 2023. Mother tubers of wild potato Solanum jamesii can make shoots five times. American Journal of Potato Research. 2023 (1-6). https://doi.org/10.1007/s12230-023-09927-1.
Díaz-García, G., Enciso-Maldonado, G., Diaz-Garcia, L., Legaria-Solano, J., Bamberg, J.B., Lozoya-Saldana, H. 2024. Field screening of Solanum demissum confirms its late blight resistance in the Toluca Valley, Mexico. American Journal of Potato Research. 1-10 (2024). https://doi.org/10.1007/s12230-024-09945-7.
