1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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
3. Progress Report:
This report documents progress for project 2050-21000-035-00D, which started March 2018 and continues research from project 2050-21000-032-00D, "Potato Genetic Improvement for Western U.S. Production." Contributing to Objective 1 and its Sub-objectives, several thousand breeding clones were tested for the presence of virus, planted, maintained, and harvested at multiple sites for seed increase. Clones were also evaluated for yield and disease resistance. Two hundred and eight parents were grown in the greenhouse and hybridizations made among them to generate true potato seed, which is the starting point for new breeding populations. Included within the 208 parents were parental clones with resistance to potato cyst nematode and tuber necrotic viruses (Potato virus Y, Potato mop-top virus, and Tobacco rattle virus), thereby contributing to both Objectives 1 and 3. Approximately 52,000 true potato seed were germinated and transplanted to pots in the greenhouse to produce seedling tubers that will become the first field generation material in 2019. Another 52,000 seedlings will also be grown and seedling tubers generated in the fall and winter of 2018-2019, for a total of 104,000 first-field generation clones for planting in the spring of 2019. Marker assisted selection relating to Objective 2 was conducted beginning with second field year material. Molecular markers diagnostic for the presence of genes for resistance to Potato Virus Y, Potato leafroll virus, and potato cyst nematode were assayed, and this information was used during field selection to enable breeding for resistance to these pathogens. The project contributed to the National Fry Processing Trial, which is sown at six sites nationally and seeks to identify potential new processing varieties with low tuber sugars and associated low acrylamide concentrations in processed potato products. Acrylamide has been identified as potentially detrimental to human health, with the potato processing industry actively engaged in reducing acrylamide concentrations in processed potato products through support of this work. Entries for the trial comprise breeding clones from potato breeding programs throughout the U.S. This project contributed 13 of the 38 entries in the 2018 trial and planted, maintained, harvested, and collected data for the Idaho trial site. Research efforts in the National Fry Processing Trial contribute directly to Sub-objective 1B. A manuscript detailing resistance to three species of potato cyst nematode within program germplasm was submitted and accepted for publication. The data presented in the publication will enhance the project’s ability to screen for resistance to these pathogens, thereby contributing to Objective 3.
Endelman, J.B., Schmitz Carley, C.A., Bethke, P.C., Coombs, J.J., Clough, M., Da Silva, W., De Jong, W.S., Douches, D.S., Frederick, C.M., Haynes, K.G., Holm, D.G., Miller, J., Munoz, P., Navarro, F.M., Novy, R.G., Palta, J.P., Porter, G.A., Rak, K., Sathuvalli, V., Thompson, A.L., Yencho, G. 2018. Genetic variance partitioning and genome-wide prediction with allele dosage information in autotetraploid potato. Genetics. 209:77-87. https://doi.org/10.1534/genetics.118.300685.