ARS | Publication request: Evaluation of Verticillium Wilt Resistance in Russet Norkotah and Six Strain Selections

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 3, 2010
Publication Date: July 7, 2010
Citation: Jansky, S.H., Miller, J.C. 2010. Evaluation of Verticillium Wilt Resistance in Russet Norkotah and Six Strain Selections. American Journal of Potato Research. Available:http://www.springerlink.com/content/j1w51303k0576246/fulltext.pdf.

Interpretive Summary: Russet Norkotah is a fresh market potato variety with exceptional tuber appearance. However, plants of this variety are small and weak. Breeders have selected for plants with improved yield and vigor, creating several strain selections. The strain selections show fewer disease symptoms than Russet Norkotah when challenged with the soil-borne fungal pathogen Verticillium dahliae. This study was carried out to determine whether the strain selections are, in fact, more resistant to Verticillium wilt than Russet Norkotah. The strains show less symptom expression, but they are also later in maturity. They do not resist colonization of the stems by the fungus any better than Russet Norkotah does. In addition, the strains do not yield any more than Russet Norkotah in the presence of the pathogen. Consequently, the resistance reported in Russet Norkotah strains is due to immature plant physiology rather than a mechanism to limit the growth of the fungus in stem tissues.

Technical Abstract: Strain selections of Russet Norkotah have been selected for enhanced vigor and high yield. In addition, they exhibit less severe expression of disease symptoms on the presence of Verticillium dahliae, a soil-borne fungal pathogen that causes Verticillium wilt. However, this apparent resistance may be due to late maturity in the strain selections. This study was designed to compare the levels of Verticillium wilt resistance in Russet Norkotah with six strain selections. In two years, trials were carried out on a V. dahliae infested field and an adjacent fumigated field. Comparisons were made between Russet Norkotah and its strains for maturity, symptom expression, stem colonization, and tuber yield. Compared to Russet Norkotah, the strains were later in maturity, exhibited fewer Verticillium wilt symptoms and were higher yielding in the absence of V. dahliae. However, they were similar to Russet Norkotah in stem colonization and yield in the presence of the pathogen. Apparent resistance in the strain selections appears to be due to immature plant physiology rather than their ability to limit fungal growth and reproduction in stem tissues.