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Response of Six Potato Cultivars to Amount of Applied Water and Verticillium dahliae

First and third authors: Orbiting Astronomical Observatory (OAO) c/o United States Environmental Protection Agency (USEPA), 200 SW Western, Corvallis, OR 97331-2902; second author: Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331-2902; and fourth author: USEPA, 200 SW 35th Street, Corvallis, OR 97333

Six potato cultivars were grown with or without the addition of Verticillium dahliae inoculum and were watered at 50, 75, or 100% estimated consumptive use. The applied water × cultivar interaction was significant (P = 0.009 and P = 0.001 for 1996 and 1997, respectively) for the relative area under the senescence progress curve (RAUSPC). With a decrease in water, there was an increase in RAUSPC. A significant interaction of inoculum density × cultivar also was found, based on RAUSPC (P = 0.0194 and P = 0.0033 for 1996 and 1997, respectively). In V. dahliae-infested plots, ‘Katahdin’ and ‘Ranger Russet’ were resistant to Verticillium wilt. Population size of V. dahliae in stem apices was significantly lower in ‘Katahdin’ in both 1996 and 1997 (P = 0.0001) and in ‘Ranger Russet’ in 1997 (P = 0.0001) than in the other cultivars. ‘Russet Burbank’ and ‘Shepody’ had large apical stem populations of V. dahliae and higher RAUSPC values associated with both V. dahliae inoculum and decreased amount of applied water. Marketable tuber yield was unaffected by V. dahliae in both years. Cultivar resistance to Verticillium wilt was related to cultivar tolerance to moisture deficit stress. Results suggest that moisture deficit stress response has the potential to be a useful tool in protocols for screening potato for Verticillium resistance.

Additional keywords: drought tolerance, potato early dying, Solanum tuberosum.