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.
This project is focused on further developing a molecular marker for resistance to verticillium wilt, a widespread problem for potato growers nationwide. We had previously identified a gene in potato that correlates with resistance and developed a way to track it in populations generated during breeding. However, the marker to track the gene is very specific for a certain source of resistance, Solanum chacoense. We are now looking at differences within this gene in other resistant or susceptible wild species of potato in order to expand the usefulness of the marker to breeders. A postdoctoral fellow has been hired to complete the objectives and has screened 17 different wild species of potato in order to determine whether they are resistant or susceptible. Six of these species, including both resistant and susceptible plants, were used to sequence the Deoxyribonucleic acid (DNA) of the gene of interest, which is similar to the Ve gene of tomato that also confers resistance to Verticillium. We have amplified Ve-like sequences from these species and are in the process of identifying differences in the DNA that might determine whether the plant is resistant or susceptible. Using this information, we will identify DNA differences that are conserved among resistant plants from multiple species, which will expand the usefulness of genetic markers associated with this gene. The scientists associated with the project meet on a weekly basis to discuss progress on the project.