Location: Temperate Tree Fruit and Vegetable Research
Project Number: 2092-21220-002-000-D
Project Type: In-House Appropriated
Start Date: Mar 7, 2018
End Date: Mar 6, 2023
Objective:
Develop or identify new breeding lines, germplasm and named cultivars with superior quality, disease and pest resistance, and nutritional value. This will involve collaborative and independent work by our three-person team using our respective expertise in potato breeding, molecular physiology and plant pathology. The three objectives below undertake complimentary approaches to germplasm improvement. Objective 1 involves largely breeding for targeted traits. Objective 2 seeks to determine basic mechanisms that govern trait expression. Objective 3 will develop new or improved methods to evaluate breeding lines and germplasm. We will work closely with the TriState Breeding Program, as we have for over 20 years.
Objective 1: Evaluate, identify, breed, and release potato germplasm with improved traits of interest, especially improved disease and pest resistance, and increased amounts of phytonutrients.
Subobjective 1A. Develop breeding lines, cultivars or identify germplasm with enhanced amounts of phytonutrients and visual appeal.
Subobjective 1B. Develop breeding lines, cultivars or identify germplasm with superior disease resistance with a focus on soil-borne diseases.
Objective 2: Characterize genetic, environmental, molecular, physiological, and biochemical factors that control accumulation of potato phytonutrients and mechanisms that lead to plant disease resistance, and use this knowledge to produce new superior potato cultivars.
Subobjective 2A: Determine mechanisms that mediate tuber phytonutrient expression.
Subobjective 2B: Increase information and develop methods with potential to be used for control of Potato Cyst Nematode (PCN) and for improved disease resistance.
Objective 3: Develop improved pathogen diagnostic techniques and phenotyping approaches that can be used for potato germplasm evaluation, development of host-resistance, and identification of emerging potato diseases.
Subobjective 3A. Identify and characterize emerging and evolving pathogens and pests in the Pacific Northwest.
Subobjective 3B: Characterize Tobacco rattle virus (TRV)-potato interactions to develop better detection methods and determine the relationship between viral titer, cultivar, symptoms and resistance.
Objective 4. Determine the value of advanced potato germplasm with particular attention to disease, pest, and stress resistance, yield, quality characteristics, and profitability parameters. Define cultural conditions which will optimize yield and quality of each clone.
Approach:
1A. Germplasm will be intercrossed and progeny evaluated in the field. Replicated plots will be grown in successive years across multiple locations. Lines will be analyzed for carotenoids, anthocyanins, antioxidants, total protein, potassium and iron. Molecular markers will be used to characterize high carotenoid lines. Liquid chromatography mass spectrometry (LC-MS) will be used to quantitate phytonutrients. If germplasm does not provide the desired traits, we will import additional germplasm.
1B. Resistance to nematodes, viruses and fungi will be developed using resistant lines to make crosses and evaluating progeny in field trials. Selected clones will be evaluated under high disease pressure and molecular markers used for Meloidogyne chitwoodi breeding. If progeny have lower selection rates than expected the size of the initial population will be increased.
2A. Expression of structural genes and transcription factors in potatoes or organs that have low or high amounts of phenolics, are cold-treated, or wounded will be analyzed using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and LCMS. We will use ribonucleic acid sequencing (RNA-seq) to generate transcriptomic data. Effect of environment on glycoalkaloids will be assessed by growing 13 genotypes in six locations and methanolic extracts from freeze-dried tubers analyzed by LCMS. If key genes are identified, resources will be redirected to apply this knowledge through precision breeding efforts.
2B. Potato cyst nematode (PCN) trap crop seed will be produced by sowing true seed directly into the soil at ¼ inch depth. Hatching factor purification will be tested on diverse High-performance liquid chromatography (HPLC) columns and fractions tested for activity. If a hatching factor is identified and quantitated by LCMS, increased resources will be directed.
3A. Samples from symptomatic plants will be collected. Grafting experiments will evaluate transmissibility. Established molecular tools will be used to detect any pathogens present. If targeting known pathogens does not identify a biological agent, primers that target unknown pathogens will be used. Psyllid involvement in beet-leafhopper transmitted virescence agent (BLTVA) will be tested using field and cage experiments. Development of improved diagnostic tools for BLTVA and Candidatus Liberibacter solanacearum (Lso) will be assessed using a single-tube nested PCR technique, RT-qPCR or Kompetitive allele-specific PCR. If unable to identify any known pathogen in a sample, next generation sequencing platforms will be used.
3B. Tobacco Rattle Virus (TRV) sampling methods will be evaluated for efficacy. Lines will be evaluated for resistance in field trials. PCR will be used to compare viral titer with symptom severity. Varieties will be exposed to TRV and differences in resistance/insensitivity and susceptibility compared. Daughter tuber symptoms and viral titer will be compared to mother tuber symptoms, viral titer, plant emergence, and daughter tuber yield. If TRV infection becomes sporadic, we will focus on the genotypes that were subject to sufficient disease pressure.
