Research Project: Potato Genetic Improvement for Enhanced Tuber Quality and Greater Productivity and Sustainability in Western U.S. Production

Location: Small Grains and Potato Germplasm Research

2023 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
This is the final report for project 2050-21000-035-000D, Potato Genetic Improvement for Enhanced Tuber Quality and Greater Productivity and Sustainability in Western U.S. Production, which has been replaced by new project 2050-21000-036-000D, Genetic Improvement of Potato for Sustainable Production and Enhanced Tuber Qualities for the Western United States, which started March 1, 2023. For additional information, see the new project report. In support of Sub-objective 1A, several thousand potato breeding clones were hybridized, planted, maintained and evaluated at multiple sites throughout the United States. The evaluations included yield and disease screening conducted at Aberdeen and in multiple sites within Idaho and with collaborators throughout the United States. Seed of all breeding clones were maintained at three increase sites in Idaho. Breeder seed representing these clones were tested for viruses to reduce infection in seed used for planting. Varieties released during the life of the project plan include ‘Becca Rose’, ‘Rainier Russet’, ‘Echo Russet’, ‘Vanguard Russet’, ‘Galena Russet’, ‘Castle Russet’, ‘Purple Iris’, ‘Delicia’, and ‘La Belle Russet’. Parental clones were grown in greenhouses each year during the project and hybridizations were made among them for the generation of true potato seed (the starting point for the generation of new populations in the breeding program). From the successful hybridizations, true potato seed was extracted, counted, and organized each fall. In the spring, seedlings from that true potato seed were generated and grown in greenhouses to produce ‘seedling’ tubers for planting in the field each year. The harvested seedling tubers are planted each year on approximately 25 acres in Aberdeen and selections are made in the fall from this first field year material principally based on tuber type and shape. Disease evaluations done routinely each year include field evaluations for early blight, verticillium wilt, common scab, and Potato viruses X, Y, and leafroll. Evaluations for soft rot and dry rot are conducted in the lab each year on advanced breeding lines. Each plant from a tuber represents unique genetics with the potential to be developed as a new variety. Directed hybridizations are made specifically for disease and pest resistance, as well as for better tuber quality, enhanced nutritional qualities, traits which require less fertilizer, water, and other inputs to make potato more sustainable. These research efforts contribute to all four sub-objectives of Objective 1. In support of Sub-objective 1B, the National Fry Processing Trials (NFPT), financially supported by the potato processing industry, started in 2011. This project has provided roughly a third of the entries for this trial over each of the last five years. Our project serves as one of six trial sites for the NFPT where entries were planted, maintained, and data collected and provided to the national project. The NFPT program seeks to identify advanced breeding clones that perform well under multiple environments and have low tuber sugars (reducing sugars) for processing. This program provided 32 of the entries (breeding clones) of the total 66 entries from seven states in 2022. In support of Sub-objective 1C, advanced breeding clones were evaluated for nitrogen use efficiencies, with further development of protocols for water use efficiency trials. This work was done in collaboration with the University of Idaho as part of the Northwest Potato Variety Development Program. These trials were conducted at Aberdeen, Idaho. In support of Sub-objective 1D, data was gathered with the help of collaborators in assessing advanced breeding clones from the Aberdeen potato breeding program. This included evaluating vitamin C and glycoalkaloid content in tubers as well as assessments for protein and other components present in potato tubers. Collaborating institutions included the University of Idaho and Washington State University. In support of Objective 2, use of marker-assisted selection was routinely employed to accelerate breeding for resistance to recurrent and emerging potato pathogens and pests that impact the western United States. Research has resulted in the development of a multi-plex PCR assay to streamline identification of three key Potato virus Y resistance genes. This assay has allowed more rapid selection at harvest of promising lines that carry one or more Ry genes. Additionally, this assay has been used to mine the germplasm in the program which led to the discovery of Rychc associated markers where the virus resistance source was previously unidentified. There are now multiple entries in the second year and later material with pyramided genes of Ryadg, Rysto, and Rychc. Molecular markers were used to identify nematode resistance on this project’s second year germplasm. Second year material is being screened on an annual basis by a university collaborator. Research was summarized and published in support of Objective 3 which characterized foliar and tuber reactions to multiple PVY strains in 60 potato viruses and four market classes. This work was done prior to release of a new variety and was done on widely grown existing varieties. Potato mop-top virus trials were established in two locations in Idaho, one on a commercial farm, and one on a research farm, allowing replication of the same experiment in a long season area and in a short season area. Both sites were evaluated in a similar manner for tuber symptoms and for the presence of virus in asymptomatic tubers in order to determine virus resistance. Hybridizations were done over the life of the project for resistance to the white potato cyst nematode (PCN, G. pallida) as well as the golden nematode (G. rostochiensis) and for G. ellingtonae. These hybridizations were crossed using pollen and flowers from parental clones where at least one had PCN resistance. Each spring entries have been sent to three nematology labs for the phenotyping against Globodera rostochiensis, specifically against the Ro2 pathotype and against G. pallida and G. ellingtonae. Additional parental material has been brought into the program from Europe and South America allowing introgression and pyramiding of GpaIVadg and Gpa5 genes resulting in the potential for higher resistance to G. pallida than currently exists in the program.

Accomplishments

Review Publications
Sotomayor, D.A., Ellis, D., Salas, A., Gomez, R., Sanchez, R.A., Carrillo, F., Giron, C., Quispe, V., Manrique, N., Anglin, N.L., Zorilla, C. 2023. Collecting wild potato species (Solanum sect. Petota) in Peru to enhance genetic representation and fill gaps in ex situ collections. Frontiers in Plant Science. 14. Article 1044718. https://doi.org/10.3389/fpls.2023.1044718.
Vollmer, R., Villagaray, R., Castro, M., Cardenas, J., Pineda, S., Espirilla, J., Anglin, N.L., Ellis, D., Azevedo, V. 2022. The world’s largest potato cryobank at the International Potato Center (CIP) – status quo, protocol improvement through large-scale experiments and long-term monitoring. Frontiers in Plant Science. 13. Article 1059817. https://doi.org/10.3389/fpls.2022.1059817.
Baley, N., Sathuvalli, V., Charlton, B., Shock, C., Yilma, S., Qin, R., Feibert, E., Vales, M., Novy, R.G., Whitworth, J.L., Brown, C., Navarre, D.A., Stark, J.C., Pavek, M., Knowles, N.R., Knowles, L., Blauer, J., Brandt, T., Wang, Y., Spear, R., Olsen, N. 2022. Echo russet: A russet potato variety with a high yield of marketable tubers, high processing quality, and few tuber defects. American Journal of Potato Research. 100:15-26. https://doi.org/10.1007/s12230-022-09891-2.
Griffel, L.M., Delparte, D.M., Whitworth, J.L., Bodily, P.M., Hartley, D.S. 2022. Evaluation of artificial neural network performance for classification of potato plants infected with potato virus Y using spectral data on multiple varieties and genotypes. Smart Agricultural Technology. 3. Article 100101. https://doi.org/10.1016/j.atech.2022.100101.