Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2005
Publication Date: 8/1/2005
Citation: Choppakatla, V., Melouk, H.A., Hunger, H.M., Payton, M.E., Chenault, K.D. 2005. Production of endo-polygalacturonase by Sclerotium rolfsii [abstract]. Phytopathology. 95:S20. Interpretive Summary:
Technical Abstract: Sclerotium rolfsii produces oxalic acid and endo-polygalacturonase (endo-PG) to facilitate infection and degradation of host tissues. Our studies of pathogenicity showed that isolates of S. rolfsii from peanut are highly virulent on peanut and wheat, whereas isolates from wheat are lowly virulent. Since oxalic acid levels produced by these isolates is nearly equivalent, it was hypothesized that endo-PG may be the determinant factor for pathogenicity. The extracellular activity of endo-PG produced by a peanut isolate (Melouk) and a wheat isolate (Wheat) was determined at different culture ages (3, 5 and 7 days) using a viscosity reduction assay (VRA) and a reducing sugar assay (RSA). Polygalacturonic acid was used as a substrate for both assays. As determined by VRA and RSA, endo-PG activity was low on day 3 but showed an increase at day 5. Culture filtrates from isolate Melouk had significantly higher endo-PG activity starting at day 5 than the isolate Wheat. Increased enzyme activity was not associated with mycelial growth, which suggests that secretion of endo-PG does not necessarily require high mycelial growth. Results from this study suggest that endo-PG may be contributing to the difference in pathogenicity between these two isolates.