Location:2013 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 to 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. BSL: BL1 recertified 6/20/07.
3. Progress Report:
This is the final report for this project, replaced by 5354-21220-011-00D. The research protects the sustainability of the potato industry, keeps potatoes affordable by reducing losses to disease and develops potatoes with even higher amounts of phytonutrients. Two new high-antioxidant varieties with purple or red flesh were released. Two genes were shown to have a key role in controlling potato carotenoid content. Analysis of the broad-sense heritability of potato minerals suggest levels can be increased by breeding. Higher-throughput LCMS analytical techniques that expand our ability to evaluate potato breeding lines for phytonutrients were developed. Biochemical and molecular changes that alter tuber phytonutrient expression in response to environment were discovered. Immature tubers were found to have higher amounts of many phytonutrients. Expression of genes involved in phenylpropanoid, carbohydrate or shikimate metabolism were correlated with metabolite pools. Over 200 genotypes were assessed in three years of field trials for “baby potato” phytonutrient and agronomic qualities. Various cooking methods did not decrease phenylpropanoids or vitamin C in baby potatoes. These potatoes are sought for their taste, faster preparation and gourmet appeal; Information about their phytonutrients could create new markets. Two human feeding studies by collaborators using purple potatoes showed increased serum antioxidants, reduced blood pressure and inflammation markers. A correlation was found between the new “zebra chip” (ZC) disease and the potato psyllid, which allowed targeted control efforts to reduce losses. We validated a technique for testing large numbers of psyllids and helped screen large amounts of germplasm for genetic resistance. HPLC analysis suggested increases in tyrosine cause the ZC tuber browning. To combat the new potato cyst nematode (PCN) threat, over 100 crops were screened to identify potential trap crops. S. sisymbriifolium caused the Idaho population to hatch and did not allow reproduction. Improved versions of S. sisymbriifolium were made with greater root mass or reduced thorns. LCMS analysis suggests at least ten hatching factors exist, purification of which would help PCN eradication. Sources of resistance to powdery scab and black dot were found and incorporated into our breeding program, as was resistance to the costly pest, Columbia Root-knot nematode. Resistance in the roots was discovered to be separate from tuber resistance. A standardized method for detection of 11 viruses and one viroid of potato was developed, along with tests to rapidly differentiate PVY-O from PVY-N:O; this aids detection of these viruses in grower’s fields and seed lots, reducing their economic impact. Work with collaborators clarified the role of salicylic acid in regulating plant disease resistance and showed important interactions with fatty acid signaling that modulate plant resistance to disease. Our new 5-year project will build upon these findings to develop germplasm with superior disease/pest resistance or nutritional qualities, understand mechanisms that influence these traits and identify superior disease management options.
1. Different genetic populations of potato psyllid identified. Different genetic populations of the potato psyllid were identified that transmit the bacterium that causes the damaging potato zebra chip disease (ZC). We found there are four distinct genetic variants of the potato psyllid in the United States that roughly correspond to geographically distinct regions of the country. This finding suggests there are complex interactions between the bacterium and the psyllids in these different areas, which would help explain the differences among ZC incidence in different parts of the country. These insect populations may vary in their ability to transmit the bacterium or survive the winter in cold northern areas of the country. This information brings us closer to understanding and controlling ZC, which has caused tens of millions of dollars in crop losses.
2. Discovered that immature (“baby”) potatoes have higher amounts of various phytonutrients. Metabolite-gene expression relationships were measured and both early and late branches of the phenylpropanoid pathway were more active in immature tubers. Carotenoid gene expression and total protein were also found to be more active. Candidate transcription factors that regulate phenylpropanoids were examined, and one MYB was identified that appears to be a major player in regulating tuber antioxidant content. This provides insights into mechanisms that control potato phytonutrients, expands the number of phytonutrients known to be present at higher concentrations in baby potatoes, and suggests that these types of potatoes may appeal to health-conscious consumers.
3. Columbia root-knot nematode and potato virus Y are serious pathogens of potato in the Columbia Basin of the Pacific Northwest. A time and cost-saving method of selecting for resistance is to use DNA markers to pre-determine the resistance status. USDA/ARS and WSU scientists have discovered that plants with both resistances are disproportionately poor in horticultural type. However, using the DNA markers, we have been able to select doubly resistant progeny from crosses in which this association has been broken resulting in superior horticultural type combined with resistance to nematodes and virus. One hundred twenty million dollars are spent annually to control these two diseases in the Pacific Northwest. Selection of new varieties with double resistance will help to cut these costs by 75%.
4. Improvements in developing improved PCN Trap crops. The new pest Pale Cyst Nematode was found in Idaho in 2006 for the first time and the infested fields remain under quarantine. Eradication of this pest has been attempted using soil fumigants, but an alternative is to grow Solanum sisymbriifolium (Litchi tomato), a plant which induces the nematode eggs to hatch, while not providing a suitable host. In the absence of a host the hatched juveniles die quickly in the soil. Litchi is inconveniently covered with long sharp prickles. We have developed a population of Litchi tomato which is effective in eradicating Pale Cyst Nematode and is further improved in that it has shorter and fewer prickles on the stem. These results facilitate the use of Litchi tomato by growers to eradicate PCN and provide an alternative to methyl bromide.
5. Linking variation in genes to valuable traits in elite cultivated potato and tomato germplasm. Solanaceae Coordinated Agricultural Project (SolCAP) is focused on linking variation in genes to valuable traits in elite cultivated potato and tomato germplasm. SolCAP germplasm from individual fields in Washington and Wisconsin was screened for potato tuber resistance to late blight, the most devastating potato pathogen worldwide. Eight clones were determined to be resistant at both locations and represent the most robust potato germplasm with resistance to this major potato pathogen. This work is a step towards identifying genes with late blight tuber resistance and improving food securitySwisher, K.D., Munyaneza, J.E., Crosslin, J. 2013. Temporal analysis of potato psyllid haplotypes in the United States. Environmental Entomology. 42:381-393.