Location: Small Grains and Potato Germplasm Research
2020 Annual Report
Objectives
This project intends to produce improved potato germplasm and varieties with emphasis on the predominant market class for the western U.S. which is characterized by long tubers and russet skin. Improved varieties will be suitable for potato processing, as well as fresh consumption. The objectives below will be the specific focus for the next five years for the project scientists Novy and Whitworth:
Objective 1: Use conventional and genomic technologies to develop improved potato germplasm and varieties representative of the primary market classes grown in the western U.S. with the following enhancements being emphasized:
• Subobjective 1A: Improve Disease and Pest Resistance
• Subobjective 1B: Improve Tuber Qualities for Processing and Fresh Use
• Subobjective 1C: Reduce Production Inputs
• Subobjective 1D: Enhance Nutritional Value
Objective 2: Accelerate breeding for resistance to potato pathogens and pests using genomic technologies.
Objective 3: Identify and utilize pathogen and pest resistance specific to potato cyst nematode (PCN) and tuber necrotic viruses (Potato virus Y, Potato mop-top virus, and Tobacco rattle virus), and characterize foliar and tuber responses of potato varieties and germplasm to the tuber necrotic viruses.
Approach
Objective 1 is non-hypothesis driven research with the goal of developing potato germplasm and varieties with tuber qualities, disease and pest resistance, and sustainable production that is superior to current industry varieties, with emphasis on primary market classes grown in the western U.S. Varieties and germplasm obtained from other breeding programs, as well as breeding clones of species and their enhanced progeny from ARS collaborators, will be hybridized with adapted parent material in our program using a modified backcross where different cultivated parent clones are used in each backcross to minimize inbreeding depression. Progenies will be screened over multiple years for enhanced traits and agronomic performance in replicated multi-site field trials in the western U.S. Use of molecular technologies (i.e. SNP microarrays, genotyping by sequencing, MAS, and genomic selection) will accelerate development of improved germplasm and varieties. Breeding clones with enhanced traits compared to industry standard varieties will be released as new varieties or as breeding germplasm. As needed, additional germplasm from outside of our program will be requested and utilized as parental material in hybridizations to generation unique populations that expedite trait enhancement.
Objective 2 is non-hypothesis driven research utilizing molecular markers with close linkage to genes conferring pest and disease resistance. Molecular markers to resistance genes for Potato virus Y, Potato leafroll virus (PLRV), and potato cyst nematode will be utilized in marker-assisted selection (MAS). Genomic technologies, including SNP microarrays, will be used to identify new genes and quantitative trait loci (QTLs) for resistance. Mapped genes and QTLs will be sequenced and primers developed for MAS. Development of new MAS protocols is important for breeding resistance to emerging diseases (i.e. Potato mop-top virus (PMTV) and zebra chip disease. MAS application will fast-track identification of resistant individuals and facilitate the development and release of potato germplasm and varieties with enhanced disease resistance. If markers in the literature prove unsatisfactory for MAS, then we would work to identify suitable markers, as was previously done by our project for a PLRV resistance gene.
Objective 3 is non-hypothesis research focusing on the screening of diverse potato germplasm and characterization of infection-response to potato cyst nematode and three tuber necrotic viruses: PVY, (PMTV), and Tobacco rattle virus (TRV). Field evaluations for response to infection will be conducted by our project (PVY), as well as with collaborators in Washington and North Dakota (PMTV and TRV). Resistant individuals will be utilized in the breeding program as parents with incorporation of resistance conducted utilizing the modified backcross method describe in Objective 1. If levels of resistance for PCN and the tuber necrotic viruses cannot be identified within project germplasm, then new parental material with desired characteristics will be obtained from the U.S. Potato Genebank and other national and international public and private breeding programs
Progress Report
In support of Objective 1, several thousand potato breeding clones were tested for viruses and planted, maintained, and harvested at multiple sites for seed increase and yield and disease trials for evaluation of their merit for continued advancement and variety release. An advanced breeding clone, A03141-6, was identified as having desirable traits for processing as fries and fresh market tablestock. It has cold sweetening resistance, meaning that when held at low temperatures that reduce sprouting, less starch is converted to reducing sugars, resulting in a lighter-colored, better-quality fry. This clone will be released as a new variety named Galena Russet. Hybridizations (crossing of the botanical flowers for producing true potato seed) were done in the greenhouse using 166 parents with more than 1,000 successful hybridizations. True seed obtained from previous years was also grown in the greenhouse to produce small seedling tubers for planting as the first-year field generation. This spring, 51,174 seedlings from true seed were planted and will produce seedling tubers for planting in the field in 2021. A second crop of 52,174 seedlings will be grown in the fall and combined with the first crop for a total of 103,348 seedling tubers to be planted. In May 2020 a total of 100,500 seedling tubers from 662 families were planted in the field for fall selection. Each plant from a tuber represents unique genetics with the potential to be developed as a new variety. Within these numbers are directed hybridizations made specifically for disease and pest resistance, as well as for better tuber quality, enhanced nutritional qualities, and traits which require less fertilizer, water and other inputs in order to make potato more sustainable. These research efforts contribute to all four sub-objectives of Objective 1.
Coordinated National Fry Processing Trials (NFPT) planted across multiple states included 48 entries (breeding clones) from seven states. Eighteen of those entries originated from the ARS breeding program. The NFPT program seeks to identify breeding clones that perform well under multiple environments and have low tuber sugar (reducing sugars) associated with low acrylamide production. Acrylamide has been identified as potentially harmful to human health. The industry and scientists have engaged in this project to proactively reduce acrylamide levels in processed potato. Our project serves as one of the six trial sites for the NFPT. Entries were planted and maintained, and data was collected and provided to the national project. These NFPT research efforts directly contribute to Sub-objective 1B.
In support of Objective 2, marker assisted selection was conducted beginning with second-field year material. Molecular markers that indicate the presence of genes for resistance to Potato virus Y (PVY), Potato leafroll virus, and potato cyst nematode were tested, and this information was used during field selection to facilitate the breeding for resistance to these diseases and pests. A postdoctoral associate developed a ‘multiplex’ assay that allows breeding lines to be tested for the presence of three PVY resistance genes, rather than having to conduct three separate tests, thereby allowing higher throughput testing. These efforts support Objectives 2 and 3. Another postdoctoral associate is identifying molecular markers associated with important tuber traits and disease resistance contributing directly to Sub-objectives 1A and 1B and Objective 2.
In support of Objective 3, research was initiated to evaluate two ARS-developed varieties, Castle Russet and Pomerelle Russet in a Potato mop-top virus (PMTV) infested field. PMTV can cause tissue death in tubers resulting in a quality defect. Virus disease incidence and severity, as well as yield, were recorded. Results will be used to determine if the varieties are resistant or just insensitive to the virus symptoms. The field was also grid sampled for the pathogen (Spongospora subterranea) that causes powdery scab disease and serves as a vector for the virus. At present, there are no pesticide controls for the vector or the virus. The ability to identify infested fields and to be able to use resistant or insensitive varieties will offer the best hope for potato production in infested areas.
Accomplishments
1. New potato variety, Galena Russet, with high yield and attractive tubers suitable for multiple uses. ARS scientists in Aberdeen, Idaho, along with the experiment stations in Idaho, Washington, and Oregon, released and filed for Plant Variety Protection (PVP) for Galena Russet, a new potato variety that produces a high yield in both early- and full-season harvests, allowing for use over more growing areas. This variety has excellent processing characteristics for fries due to cold sweetening resistance, allowing for lighter colored fries late in the storage season. This is an improvement over other varieties, where conversion of starch to sugar results in a darker product. Galena Russet has an attractive tuber shape and low levels of tuber defects, making this a good fresh market potato.
Review Publications
Cruzado, R., Rashidi, M., Olsen, N., Novy, R.G., Wenninger, E.J., Bosque-Perez, N.A., Karasev, A., Price, W.J., Rashed, A. 2020. Effect of the level of “Candidatus Liberibacter solanacearum” infection on the development of zebra chip disease in different potato genotypes at harvest and post storage. PLoS One. 15(4). https://doi.org/10.1371/journal.pone.0231973.
Stark, J., Thompson, S., Novy, R.G., Love, S. 2020. Variety selection and management. In: Stark, J.C., Thornton, M., Nolte, P., editors. Potato Production Systems. 2nd edition. Cham, Switzerland: Springer Nature. p. 35-64. https://doi.org/10.1007/978-3-030-39157-7
Huang, D., Yan, G., Gudmestad, N.C., Whitworth, J.L. 2019. Assessment of factors associated with real-time PCR quantification of Paratrichodorus allius from field soil DNA. Plant Disease. 103(12):3265-3273. https://doi.org/10.1094/PDIS-12-18-2240-RE.
Whitworth, J.L., Selstedt, R.A., Westra, A.A., Nolte, P., Duellman, K., Yellareddygari, S., Gudmestad, N.C. 2019. Symptom expression of mainstream and specialty potato cultivars to bacterial ring rot (Clavibacter sepedonicus) and evaluation of in-field detection. American Journal of Potato Research. 96:427-444. https://doi.org/10.1007/s12230-019-09730-x.
Westra, A., Nolte, P., Whitworth, J.L., Durrin, J.S. 2020. Seed potato production and certification. In: Stark, J.C, Thornton, M., Nolte, P., editors. Potato Production Systems. Cham, Switzerland: Springer Nature. p. 65-86. https://doi.org/10.1007/978-3-030-39157-7.
Elison, G.L., Hall, D.G., Novy, R.G., Whitworth, J.L. 2020. Development and application of a large-scale multiplex marker assay to detect PVY resistance sources in Solanum tuberosum. American Journal of Potato Research. 97:289-296. https://doi.org/10.1007/s12230-020-09777-1.
Dandurand, L.M., Zasada, I.A., Wang, X., Mimee, B., Dejong, W., Novy, R.G., Whitworth, J.L., Kuhl, J. 2019. Current status of potato cyst nematodes in the United States and Canada. Annual Review of Phytopathology. 57:117-133. https://doi.org/10.1146/annurev-phyto-082718-100254.
Fife, A.N., Cruzado, K., Rashed, A., Novy, R.G., Wenninger, E.J. 2020. Potato psyllid (Hemiptera: Triozidae) behavior on three potato genotypes with tolerance to ‘candidatus liberibacter solanacearum’. Journal of Insect Science. 20(2). https://doi.org/10.1093/jisesa/ieaa020.
