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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Research Project #425150

Research Project: Potato Germplasm Improvement for Disease Resistance and Superior Nutritional Content

Location: Temperate Tree Fruit and Vegetable Research

2014 Annual Report

Objective 1: Apply genetic analyses, metabolic engineering, and targeted metabolic profiling to elucidate genetic, molecular, and biochemical factors governing host disease resistance and accumulation of select phytonutrients and vitamins in potatoes. Sub-objective 1.A. Characterize molecular and biochemical factors that modulate phytonutrient content. Sub-objective 1.B. Characterize molecular and biochemical mechanisms involved in disease/pest resistance. Objective 2: Evaluate, breed, and release potato germplasm with increased amounts of phytonutrients, which are suitable for the processing and fresh potato market, as well as for niche markets. Objective 3: Identify and release germplasm or varieties with improved resistance to powdery scab, black dot, Columbia root-knot nematode, zebra chip, potato mop top virus, potato cyst nematode, and examine the role of micronutrients in host resistance to Verticillium wilt. Sub-objective 3.A: Nematodes: Focus on identifying and developing germplasm, including trap crops, that can provide superior control options for Columbia root-knot nematode or Potato Cyst Nematode. Sub-objective 3B: Soil borne pathogens: Develop superior germplasm or management options for soil borne pathogens including powdery scab, potato mop top virus, black dot and Verticillium wilt. Objective 4: Determine available host-plant resistance and epidemiological parameters, and develop diagnostic tests for emerging pests and pathogens of potato such as zebra chip.

Objective 1: We will utilize molecular physiology approaches, including measuring gene expression, enzyme activity and metabolite pools by hyphenated techniques. Structural genes and regulatory genes will be assessed using transient assays or stable transgenics. The phenylpropanoid pathway will be a focus. HQT expression will be reduced using RNAi. LCMS will be used to assess differences in phenylpropanoids between wild type and silenced lines and the expression of at least 10-20 phenylpropanoid genes measured by qPCR. Another gene targeted for silencing will be dihydroflavonol-4-reductase (DFR). LCMS and GCMS analysis will be used to examine how phenylpropanoid and primary metabolism is reprogrammed in plants with altered DFR metabolism. MYB transcription factors will be identified in silico based on phylogenetic and protein similarity with known transcription factors. Function will be assessed in transient and stable assays. Compounds that cause the hatching of potato cyst nematode eggs will be partially purified from root extracts using chromatographic methods. Objective 2: Tuberling populations will be assembled and grown two successive seasons in the Klamath Basin of Oregon in unreplicated plots. Promising material will be analyzed for carotenoids, anthocyanins, antioxidants, and a range of other metabolites to select clones with high phytonutrient content. Statistically the data will be analyzed as a mixed model with locations, clones and interaction as fixed effects and reps within locations as random effects. We will use molecular markers to characterize hybrids and assure that we intercross only duplex Zep1 hybrids. Objective 3: We will combine PVY extreme resistance and CRKN resistant germplasm. The genetic nature will be explored by determining segregation ratios in reciprocal crosses. Mitochondrial fingerprinting will be expulsed as a diagnostic genetic marker of the restored phenotype. Crosses will be made to select a less spiny version of Solanum sisymbriifolium for use as a PCN trap crop. A. rhizogenes will be used to attempt to make a version of the plant with greater root mass. Hatching assays will be used to screen for other plants that may be a superior PCN trap crop. Crosses will be made to generate potatoes with resistance to Black dot and Powdery scab and evaluated in field trials with a randomized complete block design with four replications and ten plants per replication. The crown and root will be scored for degree of galling and sclerotia. The effect of micronutrient supplements on Verticillium wilt resistance will be assessed in field and greenhouse trials. Macro and micronutrients will be applied in-furrow. Objective 4: Psyllids collected during the survey and additional insects collected in the Pacific Northwest will be subjected to high resolution melt (HRM) analysis of the cytochrome oxidase gene in order to differentiate genetic variants of the psyllid. Extracts will be tested by PCR methods reported in the literature at dilutions up to 1,000 to determine level of sensitivity and reliability of the various methods on different host plant tissues.

Progress Report
The primary emphasis of this project is to improve the disease resistance and nutritional value of potatoes in order to increase sustainability, profitability, and enhance food security. In multi-state trials we worked closely with other members of the Tri-State Potato Breeding Program, including University and industry personnel in evaluating and developing superior potato varieties. We identified germplasm with resistance to Potato mop-top virus and found linkage between PVY and Columbia Root-Knot Nematode resistance, which will facilitate marker assisted selection of these traits. In addition to our russet potato research, our team has a special interest in developing new “specialty potatoes,” which is a consumer-oriented project to develop and identify specialty lines with superior appearance, flavor and nutritional value. These potatoes have the potential to meet evolving consumer preferences for fresh market potatoes and provide additional options for consumers desiring a non-fried product. Substantial progress was made on objectives 1 and 2, in our efforts to understand factors that influence or regulate tuber phytonutrient content and such information can make it easier to develop high-phytonutrient potatoes. Effects of environment and development on tuber phytonutrients and gene expression were elucidated and key transcription factors that influence tuber phenylpropanoid content were identified. Our research suggests sucrose is a regulator of phytonutrient gene expression in tubers, a very important finding. This work suggests a mechanism in which the transcription factors that regulate tuber phenylpropanoids also mediate and respond to sucrose concentrations. Objective 3, the work to identify new control methods for the quarantine pest potato cyst nematode (PCN) continued. We are growing large amounts of a less spiny Solanum sisymbriifolium in order to produce large amounts of seed that can be planted in Eastern Idaho as a PCN trap crop. We have found that hatching factors that stimulate PCN hatch are present not only in root exudates, but in other tissues including leaves. For objective 4, evaluation of potato psyllid populations from around the country showed the existence of different haplotypes, which allowed us to clarify psyllid overwintering habits and better understand how zebra chip disease is spread. Mineral studies have been initiated to evaluate the effect on potato soil-borne pathogens.

1. Developing high-phytonutrient potatoes. Nationally, increased emphasis is being placed on healthy diets, with evidence showing many American consumers are increasingly demanding foods perceived to be healthy. ARS scientists in Prosser, Washington, have developed new advanced breeding lines with higher amounts of phytonutrients and delineated regulatory mechanisms that control tuber content of these compounds. Effects of environment and development on tuber phytonutrients gene expression and metabolites were elucidated and transcription factors that regulate tuber phenylpropanoid content were identified. Sucrose was found to be a key regulator of tuber phytonutrient gene expression and the same transcription factors that regulate phytonutrient content appear to regulate sucrose metabolism, a finding with broad implications because sucrose has such a central role in tuber physiology. This consumer-oriented work contributes to the ability of growers and industry to adapt to evolving consumer food preferences, thereby helping to protect tens of thousands of potato related jobs, as well as providing healthier diets.

2. Selection of potato germplasm resistant to Potato mop-top virus (PMTV). PMTV is an emerging disease in the Columbia Basin region that, when the incidence exceeds five percent, can cause the total loss of the crop that costs growers ~$3,300 per acre to grow. There is no known soil treatment to eradicate this pathogen and resistant potatoes are a critical need, so ARS scientists in Prosser, Washington, with help from Conagra Foods, conducted trials in infested fields to screen for resistant germplasm. By visual observation of internal necrosis, use of RNA detection technology and immunological testing, we identified advanced material with low incidence of internal defects and low symptomless infection of the virus. This work can help keep potatoes affordable for consumers, protect industry jobs and ensure the sustainability of one of the nation’s most fertile agricultural regions.

3. Molecular markers increase selection efficiency for both potato virus Y (PVY) and Columbia root-knot (CRKN). Columbia root-knot nematode is a serious pest in 30% of the fields in the Washington/Oregon Columbia Basin. PVY is likewise a severe threat, and promising breeding lines with resistance to CRKN are consistently susceptible to PVY. ARS scientists in Prosser, Washington, developed a breeding population with single genes for resistance to both pathogens, found that the PVY gene is closely linked to the CRKN resistance, and increased the percentage of progeny in the breeding program with double resistance. However, incorporation of resistance was associated with some undesirable tuber traits, so marker-assisted selection and intense visual selection are being used to develop lines with PVY and CRKN resistance without the undesirable traits that reduce commercial potential of these new lines. Approximately 120 million dollars is spent annually on CRKN and PVY chemical control in the Pacific Northwest.

4. Management options for controlling Verticillium wilt on potato. Yield losses associated with the potato disease Verticillium wilt can exceed 40%, and restrictions on the use of soil fumigants increase the need to develop alternative management methods. ARS scientists in Prosser, Washington, in collaboration with Oregon State University, evaluated seed, foliar and in-furrow applications of nutrients or fungicides, and early season foliar applications of phosphorus-based products in greenhouse and field trials to manage Verticillium. Under greenhouse conditions, Phosphorus 10-34 and Phosphorus 11-52 applied at 200 pounds of phosphorus per acre significantly reduced levels of Verticillium present inside stem tissue compared with the inoculated controls. In addition, a naturally occurring fungus, Penicillium oxalicum, was identified in the greenhouse as a biological control agent of Verticillium. In the field, calcium chloride applied at 10 lb/acre significantly reduced Verticillium levels by 55% in stem tissue compared to the non-treated controls and increased yield by 18.8%. These findings offer new approaches to stop Verticillium crop losses that do not rely on fumigation.

5. Developing options to combat Potato Cyst Nematode (PCN). PCN is a quarantine pest that threatens the Idaho potato industry and is extremely difficult to eliminate because it can persist in the soil for 30 years without a host. ARS scientists in Prosser, Washington, have confirmed that Litchi Tomato is an effective trap crop against PCN. They developed a line with less thorns and are propagating large amounts of seed for use by the Animal and Plant Heath Inspection Service (APHIS) in the first field trial in the United States in 2015. ARS scientists identified another potential trap crop in addition to the Litchi Tomato, which is being further characterized. Progress has been made in determining ways to extract compounds from potatoes that have potential to eradicate or control the nematode. These findings have the potential to reduce the threat posed to the U.S. potato industry by PCN.

Review Publications
Kaspar, K.L., Park, J.S., Brown, C.R., Weller, K., Ross, C., Mathison, B.D., Chew, B.P. 2013. Sensory evaluation of pigmented flesh potatoes (Solanum tuberosum L.). Food and Nutrition Sciences. 4:77-81.
Nelson, W.R., Swisher, K.D., Crosslin, J., Munyaneza, J.E. 2014. Seasonal dispersal of the potato psyllid, Bactericera cockerelli, into potato crops. Southwestern Entomologist. 39:177-186.
Arp, A., Munyaneza, J.E., Crosslin, J., Trumble, J., Bextine, B. 2014. A global comparison of Bactericera cockerelli (Hemiptera: Triozidae) microbial communities. Environmental Entomology. 43(2):344-352.
Swisher, K.D., Sengoda, V.G., Dixon, J., Munyaneza, J.E., Murphy, A.F., Rondon, S.I., Thompson, B., Karasev, A.V., Wenninger, E.J., Olsen, N., Crosslin, J. 2014. Assessing potato psyllid haplotypes in potato crops in the Pacific Northwestern United States. American Journal of Potato Research. DOI:10.1007/s12230-014-9378-8.
Novy, R.G., Whitworth, J.L., Stark, J.C., Charlton, B.A., Yilma, S., Knowles, N.R., Pavek, M.J., Spear, R.R., Brandt, T.L., Olsen, N., Thornton, M., Brown, C.R., James, S.R., Hane, D.C. 2014. Teton Russet: an early-maturing, dual-purpose potato cultivar having higher protein and vitamin C content, low Asparagine, and resistances to common scab and Fusarium dry rot. American Journal of Potato Research. 91(4):380-393.
Swisher, K.D., Crosslin, J. 2014. Restriction digestion method for haplotyping the potato psyllid, Bactericera cockerelli. Southwestern Entomologist. 39:49-56.
Arp, A., Chapman, R., Crosslin, J., Bextine, B. 2013. Low-level detection of Candidatus Liberibacter solanacearum in extracted Bactericera cockerelli (Hemiptera: Triozidae) DNA by 454 pyrosequencing. Environmental Entomology. 42:868-873.
Workneh, F., Henne, D., Goolsby, J., Crosslin, J., Whipple, S., Bradshaw, J., Rashed, A., Paetzold, L. 2013. Characterization of management and environmental factors associated with regional variations in potato zebra chip occurrence. Phytopathology. 103:1235-1242.
Swisher, K.D., Sengoda, V., Dixon, J.A., Echegaray, E., Murphey, A., Rondon, S., Munyaneza, J.E., Crosslin, J. 2013. Haplotypes of the potato psyllid, Bactericera cockerelli, on the wild host plant, Solanum dulcamara, in the Pacific Northwestern United States. American Journal of Potato Research. 90:570-577.
Liu, J., Braun, E., Qui, W., Shi, Y., Marcelino-Guimaraes, F., Navarre, D.A., Hill, J., Whitman, S. 2014. Positive and negative roles for soybean MPK6 in regulating defense responses. Molecular Plant-Microbe Interactions. 27:824-834.
Payyavula, R., Navarre, D.A., Kuhl, J., Pantoja, A. 2013. Developmental effects on phenolic, flavonol, anthocyanin, and carotenoid metabolites and gene expression in potatoes. Journal of Agricultural and Food Chemistry. 61:7357-7365.
Pillai, S., Navarre, D.A., Bamberg, J.B. 2013. Analysis of polyphenols, anthocyanins and carotenoids in tubers from Solanum tuberosum group Phureja, Stenotomum and Andigena. American Journal of Potato Research. 90:440-450.
Payyavula, R., Navarre, D.A. 2013. Transcription factors, sucrose and sucrose metabolic genes interact to regulate potato phenylpropanoid metabolism. Journal of Experimental Botany. 64:5115-5131.
Wang, J., Shine, M.B., Gao, Q., Navarre, D.A., Jiang, W., Chen, Q., Hu, G., Kachroo, A. 2014. EDS1 mediates pathogen resistance and virulence function of a bacterial effector in soybean. Plant Physiology. 165:1269-1284.
Yu, K., Soares, J., Mandal, M., Wang, C., Chanda, B., Gifford, A., Fowler, J., Navarre, D.A., Kachroo, A., Kachroo, P. 2013. A feed-back regulatory loop between glycerol-3-phosphate and lipid transfer proteins DIR1 and AZI1 mediates azelaic acid-induced systemic immunity. Plant Cell Reports. 3:1266-1278.