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 was renumbered from 3655-21000-049-16S to 3655-21220-002-03S. In order to better understand the complex relationship between the potato host and the pathogens Verticillium dahliae (Vd.) and Pratylenchus penetrans (root lesion nematode) to form the early dying complex, we are studying global gene expression within potato after inoculation. We have completed preliminary experiments to determine the best concentration of each pathogen to use in order to obtain the best symptoms. We have found that tissue culture plantlets of resistant and susceptible potato are adequate for these assays and we are in the process of refining inoculation conditions.
We are also studying the effect of genes for resistance to Verticillium in potato. We have identified a gene within potato that is similar to the resistance gene locus in tomato. Sequencing deoxyribonucleic acid (DNA) of this region within the genome is underway and we have successfully isolated one of two genes within the locus. We are using whole genome sequencing of the resistant potato to identify the second gene. This research relates to objectives 2 and 3 of the project through the identification of molecular markers associated with verticillium wilt resistance and through introgression of major resistance genes into advanced breeding materials.