J U L Y / A U G U S T 2 0 1 9 POTATO GROWER 29 oz, US No 2s and culls were not influenced by VAPAM® treatment, while 6-10 oz and >10 oz tubers were significantly influenced by VAPAM® treatment. All size cate- gories except for US No 2s were sig- nificantly influenced by genotype. A treatment x genotype interaction was observed for culls. Across all genotypes, weight of 6-10 and >10 oz tubers were significantly lower with VAPAM® treatment compared to the non-fumigated treatment (data not shown), decreasing the total yield in the fumigated treat- ment. Significant correlations between tuber yield and V. dahliae colonization, or visual wilt symp- toms, were found. A lack of signifi- cant correlation between visual wilt and colonization may be due to dif- fering maturities, vine architecture, or other factor. Colonization of Chieftain and Umatilla Russet was almost zero, while visual wilting was rated at 40-50% (Fig 1 and 2), implicating vine architecture during tuber bulking and senescence. Percentage wilt (visual symptom) was low throughout the growing season for Dakota Russet; however, colonization was high in the non- fumigated treatment (Fig 1 and 2). Specific gravity was also influenced by both VAPAM® treatment and genotype. Across all genotypes, spe- cific gravity was significantly lower with VAPAM®, compared to the non-fumigated treatment. While visual assessment has been relied upon in the past and is still used for quick notes, stem coloniza- tion quantification using the RT- PCR technique provides for a more accurate phenotypic assessment, is assisting potato breeding and improvement teams in identifying genotypes resistant to colonization, and ultimately is leading to more sustainable and improved potato cultivars for grower, industry, and stakeholder adoption. Acknowledgements We wish to thank the Northern Plains Potato Growers Association, Minnesota Area II Potato Research and Promotion Council, the RD Offutt Company and staff, The NDSU potato improvement team, and Dr. Jawahar Jyoti, for funding, hosting our trial, providing seed and other resources, support, and help throughout the experiment.