Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/7/2005
Publication Date: 2/28/2005
Citation: Weiland, J.J., Chung, K., Suttle, J.C. 2005. Cercosporin is a virulence factor in the infection of sugarbeet by cercospora beticola. 23rd Fungal Genetics Conference. Paper No. 365-146.
Technical Abstract: A portion of the CTB gene encoding an enzyme in the cercosporin biosynthetic pathway of Cercospora species was cloned from C. beticola. Using a transformation vector harboring these sequences, the endogenous CTB gene in C. beticola was disrupted by homologous recombination. Southern and northern blot analysis confirmed that transformants lacking secretion of the red pigmented cercosporin toxin possessed a disrupted CTB gene and lacked vector integration events in other regions of the genome. Five CTB mutants (ctb-delta2, -delta3, -delta21, -delta23, and -delta24) examined produced reduced cercosporin as compared to parent C. beticola isolate 303B. All isolates possessed radial growth rates indistinguishable from 303B and retained the ability to sporulate in culture. Inoculation of sugar beet plants with the five mutants induced a lower number of leaf spot lesions that expanded at a reduced rate as compared to that produced by isolate 303B. Cercosporin accumulation in leaves infected with the mutants as compared to that from leaves infected by the parent will be presented. The data indicate that cercosporin is a virulence factor in the infection of sugar beet by C. beticola.