Location: Small Grains and Potato Germplasm Research
2023 Annual Report
Objectives
Potato breeding in the United States is mainly a collaborative undertaking between public institutions with the time necessary to develop new varieties taking up to fifteen years. Molecular techniques, including high throughput marker assisted selection (MAS), can reduce the timeframe. The discovery of new or emerging diseases makes it imperative that resistance be incorporated into potato to reduce losses. Climate changes, historic droughts and the need for lower nitrogen and pesticide inputs also drive the development of new varieties. This breeding program has been in place for more than seven decades with a large germplasm base to draw upon for resistance and quality traits. The program contributes to the Northwest Potato Variety (Tri-State) Program (NPVP) representing collaborations among ARS and land grant universities of Idaho, Oregon, Washington, and the potato commissions of these states. The program has a pipeline of potential new varieties allowing release of one to three varieties each year. Industry is very involved in this program providing input that helps direct research to solve problems and develop ready to use varieties. The end result is varieties with lower environmental impact that economically support, and address industry needs.
Objective 1: Develop and release new potato varieties having traits for improved processing, pest and pathogen resistance, nutrient and water utilization, greater resiliency to environmental stress, and enhanced tuber qualities that benefit the productivity and profitability of the potato industry.
Sub-objective 1.A: Develop potato varieties with improved processing and fresh market traits.
Sub-objective 1.B: Develop potato varieties with improved pest and pathogen resistance.
Sub-objective 1.C: Develop varieties with more efficient nutrient and water utilization and greater resiliency to environmental stress.
Objective 2: Discover and incorporate resistance genes from wild and domestic potato to improve varietal resilience.
Objective 3: Develop and deploy molecular markers to accelerate the improvement of new potato varieties to meet the needs of the potato industry.
Objective 4: Research the biology of new and emerging diseases and pests in potato such as Potato mop-top virus and potato cyst nematodes and incorporate virus and nematode resistance genes.
These objectives will be reached using the dedicated efforts of a Plant Breeder Geneticist, a Molecular Geneticist, and a Plant Pathologist. Together this team with the help of five technicians will use field, greenhouse, and lab resources to execute beneficial trait hybridizations, research disease interactions, seek new molecular markers and obtain and incorporate resistance genes from multiple sources. Within the scope of the project plan’s timeline, up to fifteen new varieties will be released, higher throughput evaluations will be developed to identify and select resistant progeny, and a better understanding of interactions between pests and host resistance genes will be developed.
Approach
Objective 1 -develop and release improved trait potato varieties. Sub-obj.1a -improve process and fresh market traits by selected hybridizations on russet-skin, round white, red-skin, and specialty types. Modified backcross with different parent clones will be used each cycle to reduce inbreeding depression. First year field selections and subsequent trials for yield, processing, storage, and nutritional qualities will be done as entries progress. Sub-obj.1b -developing pest and pathogen resistance in selections to be done in randomized complete block (RCB) trials for bacterial, fungal, virus and nematode resistance. Sub-obj.1c -development of varieties resilient to environmental stress (nutrient and water) will be done in RCB and split plot trials. Applications of varying amounts of water and nitrogen will mimic commercial center pivot system application. Where research doesn’t result in a new variety, germplasm releases with desirable traits will be useful in multiple breeding programs. Also, increased number of progenies can be developed to allow success. If better host resistance to pests/pathogens is unsuccessful due to low disease pressure, subsequent assays will be done on the most resistant clones. If trials for environmental resilience fail, resistant germplasm in the literature will be incorporated into trials. To increase gains over time more rigorous reduced water/nitrogen regimes will be used.
Objective 2 -discover and incorporate resistance genes to be done by germplasm exchange and backcrossing, including the use of wild diploid species to introgress traits into tetraploid potato. Marker assisted selection will increase breeding efficiencies and be used for mining germplasm for resistant sources. Unsuccessful efforts may arise due to difficulties in obtaining international germplasm or be due to different environmental flowering conditions or male sterility. Project scientists’ knowledge of phytosanitary requirements will help facilitate movement of germplasm. For male sterility, reciprocal crosses can be made with germplasm used as a female parent.
Objective 3 -develop and deploy molecular markers to be done by testing and incorporating applicable markers. Mapping populations will be geno- and phenotyped to discover QTLs associated with targeted traits. If marker development is longer than five years, incorporation of validated markers and development of QTLs for markers will occur.
Objective 4 -researching the biology of new and emerging diseases to be done by using RCB trials in infested fields. Trials will examine variety reaction to Potato mop-top virus (PMTV) and include germplasm screening for resistance. Resistant sources can be hybridized and used to develop segregating populations for genetic studies. For potato cyst nematode (PCN), putative resistant potato lines will be phenotyped in labs with Globodera nematode populations. Difficulties in finding PMTV resistant germplasm/varieties may exist in which other more diverse material will be sought, screened, and hybridized. For PCN, high G. pallida resistance may be lacking. Pyramiding genes should increase overall resistance and provide horizontal resistance.
Progress Report
This report documents progress for 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, and continues research from project 2050-21000-035-000D, Potato Genetic Improvement for Enhanced Tuber Quality and Greater Productivity and Sustainability in Western U.S. Production. For additional information, see the report for the expired project.
In support of Objective 1, research continued on new varieties with the final Plant Variety Protection documents filed on a new red-skin, white-flesh variety named ‘Becca Rose’. This variety has a better market profile than the standard red varieties, ‘Chieftain’ and ‘Dark Red Norland’ to which it was compared. It has a higher percentage of premium size yields in the two-to-six-ounce range across all three test sites than did either of the comparison varieties. ‘Becca Rose’ also has higher disease resistance for verticillium wilt, early blight, and corky ringspot compared to ‘Chieftain’. This variety supports Sub-objectives 1A and 1B for improved processing and fresh market traits as well as improved pest and pathogen resistance. Work is continuing on a Sub-objective 1C to develop varieties with more efficient nutrient and water utilization and greater resiliency to environmental stress. Additional advanced breeding clones are being developed that meet these objectives. For example, there are two russet clones with Ry genes that provide complete control of Potato virus Y (PVY) being trialed in the Western Regional Trial which covers multiple sites in Idaho, Oregon, Washington, California, Colorado, and Texas. These additional clones represent the russet market class that can be used for processing into frozen fries and other frozen products.
In support of Objective 2, seventeen clones were selected for potato cyst nematode resistance and seventeen clones were selected for resistance to Zebra chip disease. Eleven clones were selected for PVY resistance. These selections will be screened for resistance as they are derived from parents with resistance to the identified diseases. Many of the parents used in the potato cyst nematode hybridizations are new to this program, having been obtained from Europe and S. America.
Additional research continues on tuber-greening caused by exposure to light, an issue with potatoes in markets under natural or artificial light. A population derived from Solanum microdontum, a wild species has been used to identify individuals with resistance to greening while under artificial light in controlled growth chamber experiments. A previous study had shown that some accessions from Solanum microdontum did not turn green under light. The amount of tuber greening has been measured as well as the levels of glycoalkaloids, a bitter component that develops when tuber skins turn green.
In support of Objective 3, use of markers associated with PVY resistance continue to be used in the selection of second year field material. A manuscript is in preparation that shows discovery of PVY resistance that is not associated with any of the three known markers routinely used in this program to screen material for resistance. The markers used are closely linked to resistance genes Rysto, Ryadg, and Rychc. This newly found resistance may be due to the un-linking of the marker to its Ry gene in the genetic re-assortment during the breeding process or it may represent a new source of resistance. This situation where actual PVY resistance exists, as evidenced from inoculated field trials, and no markers are present, is evident in two parents that has been used for multiple hybridizations thereby allowing more detailed study of this phenomenon. Additionally, routine screening of potato selections with potato cyst nematode resistance are also being conducted using molecular markers by a university collaborator.
In support of Objective 4, research continues with plots planted in two locations this spring to evaluate the development of tuber symptoms for seven widely grown russet varieties. This is likely the last year of field work for these particular plots but work continues on the samples from previous years as they are processed for disease presence. Samples have been extracted from the tubers and are being processed with quantitative polymerase chain reaction to detect Potato mop-top virus (PMTV) and also Tobacco rattle virus which causes similar tuber symptoms and is known to exist regionally in Idaho. Results will be used to assess the risk of planting into virus-infested fields. Some varieties are susceptible to infection but do not express tuber symptoms so visual examination of tubers from a field to eliminate infected seed potato lots may not be adequate to control the spread of PMTV.
Accomplishments
1. Potato variety Teton Russet accepted by McDonalds as Gold Standard variety for their French fries. Teton Russet, developed by ARS scientists in Aberdeen, Idaho, was accepted by McDonalds for French fry production. This variety has higher vitamin C and protein and lower asparagine than the industry standard Russet Burbank. Lower asparagine contributes to lower acrylamide levels in fries and other processed potato products. The research team was also awarded a Technology Transfer award by the ARS Pacific West Area for the collaborative research that led to the variety’s development. The team included ARS, Oregon State University, and Washington State University scientists and the Potato Variety Management Institute.
