J U L Y / A U G U S T 2 0 1 9 POTATO GROWER 27 soil and avoiding pathogen infec- tion of the host, through an inte- grated approach of soil fumigation, use of resistant cultivars, green manuring, and soil solarization (Johnson and Dung 2010). In 2009, an accelerated effort to develop VW resistant cultivars was initiated as a collaborative project by Drs. Susie Thompson and Neil Gudmestad (NDSU potato breeder and potato pathologist, respective- ly). The goal is to develop durable and long-term resistance in potato genotypes, with a specific objective to screen potato germplasm, includ- ing advancing potato selections and named cultivars, for colonization by V. dahliae Kleb. In 2018, twenty-five potato geno- types, including thirteen advancing selections and twelve named culti- vars, were evaluated for resistance to V. dahliae in a field trial conduct- ed at Park Rapids, Minnesota. Two treatments, a control (soil fumigat- ed with VAPAMĀ®) and non-fumi- gated (native population of the fungi in the soil) treatment, were evaluated. Among the genotypes, Russet Norkotah (susceptible check cultivar) and Bannock Russet (resis- tant control) were included in the replicated trial. Genotypes were planted in a randomized complete block design with four replicates on May 14. Verticillium wilt visual symptoms were recorded twice a week during August as percentage wilt per plot. Stem tissue was col- lected on August 30 to quantify pathogen colonization using the RT-PCR technique. Five stems from each plot were harvested by cutting approximately 13 cm each, at the soil level, and total genomic DNA was quantified per Pasche et al. (2013). A final visual wilt rating based on a scale of 1 to 5 (1 all wilt- ed, to 5 no wilt) was recorded on September 8; vine maturity was also recorded on a scale of 1 to 5 (1 very early maturity, to 5 very late maturi- ty). The trial was harvested on October 2. Tubers were graded into four weight ranges (0-4, 4-6, 6-10, and >10 oz.). US 2s and culls were hand-picked. Specific gravity (SG) was determined using the weight in air/weight in water method. Advanced selections, AH66-4 and ND070927-2Russ, and named culti- vars, Dakota Russet and Ranger