Location:2011 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. B
3. Progress Report
A primary research effort is to develop potatoes with superior phytonutrient amount. A new cultivar (AmaRosa) was released from our program that is a fingerling with red flesh and very high antioxidants. Immature potatoes were found to contain higher amounts of some phytonutrients. Analysis of phenylpropanoid gene expression during tuber development showed that expression was higher in immature tubers and correlated with metabolite levels. Changes in sugars and carbohydrate gene expression during development were characterized to assess relationships between phytonutrients (secondary metabolism) and primary metabolism. Phytonutrients are also affected by environment. An exhaustive analysis of environmental effects of phenylpropanoid and carotenoid metabolites and gene expression was conducted on potatoes grown in Alaska, Texas or Florida and over two-fold differences in some metabolites were observed in the same genotype. A large field trial with ~90 genotypes was conducted to screen for those suitable for use as “baby potatoes” with high yields of small tubers and high phytonutrients. Transgenic approaches are underway that are designed to better understand tuber phenylpropanoid or folate metabolism by silencing or overexpressing target genes. Putative transgenic plantlets are currently in tissue culture. Research continued on the important emerging zebra chip disease of potatoes, caused by a newly described bacterium, Candidatus Liberibacter solanacearum (Lso) that is transmitted by the potato psyllid. A more rapid way to screen psyllids for Lso was developed that showed molecular detection of the bacterium was reliable in pooled insect samples of 29 Lso-free psyllids combined with one Lso-infected psyllids. We developed and validated a standardized protocol that can detect and identify eleven potato viruses and one viroid. We found all important cultivars in the Columbia Basin are susceptible to the potato purple top disease, caused by a phytoplasma found to be transmitted through tubers. Some of these tubers give rise to infected daughter plants, showing this is a risk for potato seed certification efforts. Columbia root-knot nematode is an important pest of potatoes and we have been developing resistant germplasm by utilizing wild species diversity. A resistant line was evaluated in a field trial and compared to Russet Burbank. In the absence of fumigation, this nematode resistant line outperformed Russet Burbank without damage or yield loss, whereas Russet Burbank was severely damaged. We are trying to identify hatching factors and trap crops for control of the potato cyst nematode (PCN). Solanum sisymbriifolium was identified as a potential trap crop and no PCN reproduction was observed in greenhouse assays. We have screened over 125 additional plant species seeking additional potential trap crops.