Detection methods forVerticillium species in naturally infested and inoculated soils

Abstract

The detection and identification of threeVerticillium species in field soils with a polymerase chain reaction (PCR)-based assay was compared to the traditional plating assay method. The two methods were both able to detect the commonVerticillium species in soils although the PCR method detectedV. tricorpus in three soil samples that the traditional method did not. In addition, the PCR assay was rapid, efficient, and required only 1 to 2 days for positive identification whereas the traditional methods required 4 to 8 weeks. The traditional method provided a quantitative measure of pathogen propagules in the soil with population levels ranging from 0 to 21, 625 colony-forming units per gram of soil. However, it was not able to differentiate between the weakly pathogenicV. albo-atrum strain 2 and the more aggressiveV. albo-atrum strain 1, but these two were distinguished with the PCR assay. Results from this study demonstrate that when symptoms of verticillium wilt are observed in potato plants in the field, the major verticillium wilt pathogens present in field soils can be rapidly and reliably detected by the PCR assay.