ARS | Publication request: Development of rapid pathogenicity assay for Verticillium dahliae using early flowering lettuce.

Submitted to: Phytopathology
Publication Type: Abstract
Publication Acceptance Date: March 20, 2008
Publication Date: August 20, 2008
Citation: Klosterman, S.J., Hayes, R.J. Development of rapid pathogenicity assay for Verticillium dahliae using early flowering lettuce.. Phytopathology.

Technical Abstract: Conventional assays of Verticillium wilt on lettuce require approximately three months from the time of seeding. A reduction in time required for analyses of symptom development would be useful in studies of the Verticillium dahliae-lettuce interaction. In this study, a growth chamber assay was evaluated for the rapid assessment of symptoms on lettuce. Two-week seedlings of La Brillante, Salinas, and the early flowering plant introduction (PI) 251246 were either non-inoculated or inoculated in tubes with V. dahliae conidial suspensions. The suspensions contained race 1 and race 2 isolates of V. dahliae at concentrations of 0, 1 x 103, 1 x 105, and 1 x 107/ml. Percent symptomatic leaves were recorded at 14 and 21 days, and root discoloration at 21 days. Symptoms were concentration dependent in Salinas and PI 251246, while symptom development in La Brillante was dose and race dependent, with race 2 causing significantly more root discoloration than race 1 at 1 x 107/ml. PI 251246 developed consistent leaf and root symptoms at 21 days following inoculation with race 1 and race 2 at 1 x 107/ml. Because cultivars Salinas and La Brillante exhibited inconsistent foliar symptoms and limited numbers of plants with root discoloration, the method is not suitable for selecting cultivars for resistance to Verticillium wilt. However, the use of the early flowering line PI 251246 in the tube assay provides a convenient and rapid method to analyze virulence of V. dahliae on lettuce.