ECOLOGICALLY-SOUND PEST, WATER, AND SOIL MANAGEMENT STRATEGIES FOR NORTHERN GREAT PLAINS CROPPING SYSTEMS
Location: Agricultural Systems Research Unit
Title: Enzyme-linked immunosorbent assay for cercospora beticola in soil
Submitted to: Journal of Sugarbeet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2007
Publication Date: June 1, 2007
Citation: Caesar, T., Lartey, R.T., Shelver, W.L. 2007. Enzyme-linked immunosorbent assay for cercospora beticola in soil. Journal of Sugarbeet Research. 44(1-2):51-70.
Interpretive Summary: Cercospora beticola Sacc. causes leaf spot in sugar beet and lesions in safflower. The pathogen over-winters in infected beet residue in the soil where it survives for up to 27 months. Under optimal conditions of relatively high humidity or heavy dew, spores are produced and are dispersed by wind, irrigation, rain, water, and insects to sugar beet to initiate infections. Studies in the ecology and management of C. beticola in soil, for example to determine the effect of applied biological agents or follow up changes in potential inoculum level over a period of time, have been hampered by difficulties in detecting and quantifying the amount of inoculum of this pathogen. For this purpose we developed an enzyme linked immunosorbent assay using polyclonal antibodies raised against C. beticola cell membranes. The assay detected the pathogen in two different types of naturally infested soil under two different management practices.
Soil mixed with naturally infected sugar beet residues during tillage after harvest can serve as inoculum for the leaf spot fungal pathogen Cercospora beticola when a new sugar beet crop is planted. An enzyme-linked immunosorbent assay (ELISA) was developed in an attempt to quantify the inoculum in soil. Amounts as small as 0.38 µg of freeze-dried C. beticola mycelia dispersed in carbonate buffer were detected. Fungi from different genera (Ascomycetes, Basidiomycetes, and Hyphomycetes) showed negligible cross reactivity with the polyclonal antibodies, except for the Fusarium species. To decrease cross reactivity of the antibodies to Fusarium, a pre-adsorption of the antibodies was used. Evaluation of field soil naturally infested with C. beticola showed that the assay using pre-adsorbed serum augments current detection methods and is a potential diagnostic tool for quantifying the amount of pathogen antigens in soil, therefore the potential for incidence of leaf spot disease.