1a.Objectives (from AD-416):
Verticillium wilt (VW) of potato is a widespread and persistent problem in virtually all significant production areas in the United States. The only successful control strategy currently available to growers is soil fumigation, which is expensive and environmentally harmful. Host plant resistance offers the most cost-effective long-term control strategy for VW. One likely candidate for a potato VW resistance (R) gene is an ortholog of the tomato Ve gene, which has been cloned and found to confer immunity to VW. We have recently developed a molecular marker within a Ve-like gene from resistant potato and found that this marker co-segregates with the VW resistance phenotype in a segregating population.
Our specific objectives are to:
1. Identify germplasm that has been previously documented to be either resistant or susceptible to VW and verify the resistance phenotype using quantitative PCR.
2. Amplify and sequence Ve orthologs from the resistant and susceptible individuals for use in identifying single nucleotide polymorphisms that differentiate resistant from susceptible Ve alleles.
1b.Approach (from AD-416):
Seedling inoculations of wild species populations, phenotypic characterization of the inoculated seedlings, stem DNA extraction and analysis of Ve genes from resistant and susceptible germplasm.
In order to further improve the molecular marker associated with the Ve gene, we identified and utilized 17 populations of 14 wild potato species that were either resistant or susceptible to verticillium wilt (VW). The plants were infected with V. dahliae using the dip-seedling assay and resistant and susceptible individuals were identified. We then isolated genomic deoxyribonucleic acid (DNA) and targeted the Ve gene region for sequencing. Sequencing information of the Ve region identified 37 sites within the DNA that correlated with resistance (21 sites) or susceptibility (16 sites) of the plants that were tested. This information has led to the development of a superior marker for VW resistance that can be used to track resistance derived from several wild potato species that have not been used previously in potato breeding programs.
This research relates to Objective 1, Develop adapted potato clones with enhanced resistance to major potato diseases.