Six potato cultivars were grown with or without the addition of Verticilliu
m dahliae inoculum and were watered at 50, 75, or 100% estimated consumptiv
e use. The applied water x 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 x cul
tivar also was found, based on RAUSPC (P = 0.0194 and P = 0.0033 for 1996 a
nd 1997, respectively). In V. dahliae infested plots, 'Katahdin' and 'Range
r Russet' were resistant to Verticillium wilt. Population size of V.! dahli
ae in stem apices was significantly lower in 'Katahdin' in both 1996 and 19
97 (P = 0.0001) and in 'Ranger Russet' in 1997 (P = 0.0001) than in the oth
er cultivars. 'Russet Burbank' and 'Shepody' had large apical stem populati
ons of V. dahliae and higher RAUSPC values associated with both R dahliae i
noculum and decreased amount of applied water. Marketable tuber yield was u
naffected by R dahliae in both years. Cultivar resistance to Verticillium w
ilt was related to cultivar tolerance to moisture deficit stress. Results s
uggest that moisture deficit stress response has the potential to be a usef
ul tool in protocols for screening potato for Verticillium resistance.