An improved PCR assay for species-specific detection and quantification of Cercospora beticola

Cercospora beticola causes cercospora leaf spot (CLS) on sugar beet and table beet. Accurate identification of this pathogen is critical to disease diagnosis and effective research outcomes for improved management. Several PCR assays have been described for identifying C. beticola; however, the specificity has either not been adequately tested or cross-reactions with related Cercospora species have occurred. Comparison of the three published assays for specificity to C. beticola indicated that each also amplified DNA from closely related Cercospora species. This study describes the development and subsequent assessment of conventional and quantitative PCR assays specific for detection of C. beticola. Assay specificity was confirmed across a broad range of Cercospora and other common fungal species using public DNA sequence databases and PCR. A conventional PCR assay was designed with fast PCR conditions and completed in under 40 min. The quantitative PCR assay detected 0.001-10 ng of C. beticola DNA. The effectiveness of the quantitative PCR assay to detect C. beticola DNA in diseased leaf tissue and diseased leaf tissue mixed with soil was also demonstrated. These assays provide an improved method for specific identification and quantification of C. beticola, and a valuable tool for enhancing studies into the biology of C. beticola and epidemiology of CLS.