ARS | Publication request: VARIATION IN HOST RESPONSES AMONG SELECT LETTUCE CULTIVARS TOWARDS DIVERSE ISOLATES OF V. DAHLIAE AND V. ALBO-ATRUM.

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2005
Publication Date: August 1, 2005
Citation: Vallad, G.E., Qin, Q.M., Grube, R., Hayes, R.J., Subbarao, K.V. 2005. Variation in host responses among select lettuce cultivars towards diverse isolates of v. dahliae and v. albo-atrum. Phytopathology. v. 95. pg S106.

Technical Abstract: Verticillium wilt of lettuce, caused by Verticillium dahliae, has become a major concern to the California lettuce industry. Because of limitations in cultural control practices, the incorporation of resistance into commercial lettuce cultivars is key to sustaining production in affected areas. To test the breadth of the resistance identified to date, a pair of resistant and susceptible lettuce cultivars were inoculated with a total of 29 isolates of V. dahliae and V. albo-atrum from several hosts including lettuce in a replicated greenhouse trial, and later rated for disease severity. None of the V. albo-atrum isolates or any of the isolates of V. dahliae from cruciferous hosts caused significant disease on lettuce. Most of the isolates of V. dahliae from non-cruciferous hosts (18 out of 21) caused significant disease symptoms on the susceptible lettuce cultivars, and varied in their overall virulence; whereas, only 3 of these isolates caused significant disease on the resistant lettuce cultivars. These 3 isolates were also distinct from the other non-cruciferous host isolates based on sequence data from the intergenic spacer region, raising the possibility that they form a phylogenetically distinct subgroup that differs in virulence towards specific lettuce genotypes.