Location:2012 Annual Report
1a. Objectives (from AD-416):
Objective 1. Identify superior germplasm for potato disease and pest resistance, phytonutrients, minerals and vitamins, using high-throughput methods to determine the extent of natural variation in diverse potato germplasm of select phytonutrients/metabolites. These traits will be incorporated into the cultivated breeding pool using traditional breeding and molecular approaches. Sub-objective 1.A. Identify germplasm with a range of expression of phytonutrients, study inheritance, identify associated markers, and produce superior parents. Sub-objective 1.B. Develop germplasm with resistance to pests and diseases, establishing effective and efficient screening protocols, determining range of expression, inheritance, heritability, and discover molecular markers, while mapping genetic factors where possible and useful. Sub-objective 1.C. Use metabolic profiling of multiple chemical constituents to identify sources of high expression and genotypes possessing desirable combinations. Objective 2. Determine host resistance options, epidemiological parameters and develop diagnostic tests for emerging pests and pathogens of potato. Sub-objective 2.A. Determine the impact, distribution, and importance of the soil-borne viruses tobacco rattle virus (TRV) and potato mop top virus (PMTV) on Pacific Northwest potato production. Assist in evaluating advanced germplasm for resistance to the viruses as materials become available. Sub-objective 2.B. Develop and improve diagnostic procedures for insect transmitted viruses (potato virus Y [PVY] and potato leafroll virus [PLRV]) and phytoplasmas (purple top phytoplasma and aster yellows) in potatoes. Evaluate advanced potato lines for resistance to diverse viruses. Objective 3: Elucidate genetic, molecular and biochemical factors governing host disease resistance and accumulation of select phytonutrients and vitamins. Sub-objective 3.A. Elucidate genetic, molecular and biochemical processes governing accumulation of select phytochemicals and vitamins with respect to improving potato as a food. Sub-objective 3.B. Elucidate genetic, molecular and biochemical processes involved in plant host resistance.
1b. Approach (from AD-416):
Germplasm will be surveyed for expression of disease and pest resistance, and nutraceuticals. High performing genotypes will be intercrossed with suitable commercial materials to introduce new traits into the potato breeding pool. Inheritance and genomic location will be studied using nucleic acid markers. Transgenics designed to enhance or knock out gene expression will be used to test hypotheses on gene function. Field testing will identify agronomically superior genotypes for use as parents and submission to regional yield trials.
3. Progress Report:
The potato zebra chip disease was found for the first time in the Pacific northwest in 2011. Previously this disease had only been reported in the central US, Mexico, Central America, and New Zealand. The disease is caused by a bacterium that is transmitted by the potato psyllid. Using molecular analysis ARS researchers identified three genetic variants of the potato psyllid and these corresponded to specific geographic regions of North America. The beet leafhopper transmits a phytoplasma pathogen to potatoes and other vegetables. ARS researchers in conjunction with researchers at Oregon State University found that the leafhopper was abundant in northeastern Oregon throughout the potato growing season and that a large percentage of these insects carried the phytoplasma. ARS researcher confirmed and published the first report of potato mop top virus on potatoes in Washington State. Chlorogenic acid is the major phenolic acid in potatoes and is a major contributor to the antioxidant value of tubers, has health-promoting effects in humans and is thought to contribute to plant pest/pathogen resistance. We have silenced the gene that produces chlorogenic acid and have both plants and tubers that we can now use to better define the role of chlorogenic acid in potatoes. ARS scientists at Prosser have developed the ability to evaluate numerous compounds in tubers by HPLC or LCMS analysis, and over the last year have added the ability to screen additional compounds by gas chromatography-mass spectrometry, thereby adding to the team's ability to assess changes in tuber metabolites, how metabolite composition influences crop quality and how metabolic engineering effects the tuber metabolome. Phytonutrient analysis of numerous potato genotypes has been conducted among white, yellow and purple flesh potatoes to help identify and develop varieties with superior nutritional qualities. Several field trials were conducted to evaluate germplasm, including a large trial of 80 genotypes to assess phytonutrient content of potential "baby potato" lines. The team has identified "sticky nightshade" as a trap crop that can assist in the Idaho effort to eradicate potato cyst nematode (PCN), and produced improved versions with fewer thorns or greater root mass. Work is continuing towards developing methods that can use "hatching factors" for eradication and evaluating various materials to determine whether such an approach could be scaled up to the degree necessary to treat the affected acreage. An advanced breeding line with resistance to Columbia root-knot nematode has been further tested in field trials and continues to show superior resistance compared to the industry standard, Russet Burbank. Field trials were conducted to evaluate control options for powdery scab and black dot.
1. High phytonutrient potato lines identified. ARS scientists in Prosser, Washington, have shown that immature potatoes have high amounts of phytonutrients, and demonstrated that they can lower blood pressure in a human feeding study. High phytonutrient lines were identified. Molecular and biochemical approaches showed that sucrose plays a significant role in controlling tuber phytonutrient content. This work can lead to identifying and developing health-promoting potatoes with higher amounts of phytonutrients than normal.
2. Potato mop top virus found in Washington State. There are a number of viruses that infect potatoes and these infections reduce the total yield and quality of the potato crop. One such virus, Potato mop top virus (PMTV), had been previously reported only from the states of Maine and North Dakota. In 2011, ARS scientists at Prosser, Washingon, confirmed the presence of PMTV in potatoes grown in the Columbia Basin of Washington State and published this information in the scientific literature. This information was vital in alerting potato fieldmen, certification agencies, research laboratories, and commercial laboratories that conduct potato virus disease diagnosis for the presence of this important virus in Washington State, where more than 150,000 acres of potatoes are grown.
3. Zebra Chip disease confirmed in Washington, Oregon, and Idaho for the first time. The potato zebra chip (ZC) disease is an important emerging disease of potatoes in North America, Central America, and New Zealand and is associated with a bacterium, Liberibacter solanacearum (Lso), transmitted to potatoes by the potato psyllid. In September of 2011 the disease was observed in potatoes grown in the lower Columbia Basin of Washington and Oregon, and within two weeks was also confirmed in western and south-central Idaho. Some farms suffered severe economic losses due to ZC. This information was published in the scientific literature and in extension publications to alert the potato industry of the spread of this serious disease to potato production areas in the Pacific Northwest.
4. Trap crop methods to control Potato Cyst Nematode (PCN). Potato Cyst Nematode (PCN) is a newly discovered quarantine pest found in Idaho that threatens the state’s potato crop and poses a nationwide threat to exports if it cannot be contained and eradicated. Cysts can remain viable in the soil for 30 years without a host, but if eggs can be stimulated to hatch in the absence of a host, it will kill the nematode. ARS scientists at Prosser, Washimgton, screened over 60 potential “trap crop” candidates and identified Solanum sisymbriifolium as the best. Development of superior trap crops will facilitate the eradication of PCN, protect jobs, reduce pesticide use and protect the nation’s food supply.
Crosslin, J., Rondon, S., Hamm, P. 2012. Population dynamics of the beet leafhopper in northeastern Oregon and incidence of the Columbia Basin potato purple top phytoplasma.. American Journal of Potato Research. 89:82-88.