2013 Annual Report
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):
Inoculations of seedlings from crosses between cultivated breeding parents, phenotypic characterization of the inoculated seedlings, stem DNA extraction and quantitative PCR.
This project was renumbered from 3655-21000-049-15S to 3655-21220-002-02S. An accelerated germplasm enhancement and potato breeding program has been developed to identify durable and long-term resistance to Verticillium dahliae (Vd). To accomplish this, field screening trials have been established that are highly infested with the pathogen. Cultivar Russet Norkotah was used as the susceptible control genotype and Ranger Russet, Bannock Russet, and Dakota Trailblazer cultivars were used as controls representing moderately resistance to highly resistant control genotypes. The control cultivars in addition to twenty-one additional genotypes, representing all market types, were planted in a replicated trial at Inkster, North Dakota, on May 30, 2012. Agronomic evaluations included stand and stem numbers, vine size and maturity, and visual assessment for early blight and Verticillium wilt symptoms. The development of Verticillium wilt symptoms was recorded weekly beginning mid-July through mid-September. Stems were collected in late summer to quantify the S. tuberosum:V. dahliae interaction using polymerase chain reaction (qPCR). Significant differences were found between the non-infested (control) plots and Vd-infested plots across genotypes. Results for the susceptible control, Russet Norkotah, along with ND8304-2 and ND8305-1 (two advanced chipping selections), were similar indicating that these two breeding selections are not resistant to Vd. Resistant control cultivars Bannock Russet, Dakota Trailblazer, and Ranger Russet had very low Vd colonization indices based on qPCR results. ND8068-5Russ, a very early maturing dual-purpose russet selection, was the only genotype evaluated with significant resistance to Vd. This research relates to objective 1 of the project through the identification of germplasm that is resistant to verticillium wilt and quantitation of pathogen growth in plant tissue using Quantitative polymerase chain reaction(qPCR).