Detection methods for Verticillium species in naturally infested and inoculated soils

The detection and identification of three Verticillium species in field soi ls with a polymerase chain reaction (PCR)-based assay was compared to the t raditional plating assay method. The two methods were both able to detect t he common Verticillium species in soils although the PCR method detected V. tricorpus in three soil samples that the traditional method did not. In ad dition, the PCR assay was rapid, efficient, and required only 1 to 2 days f or positive identification whereas the traditional methods required 4 to 8 weeks. The traditional method provided a quantitative measure of pathogen p ropagules in the soil with population Levels ranging from 0 to 21,625 colon y-forming units per gram of soil. However, it was not able to differentiate between the weakly pathogenic V. albo-atrum strain 2 and the more aggressi ve V. albo-atrum strain I, but these two were distinguished with the PCR as say. Results from this study demonstrate that when symptoms of verticillium wilt are observed in potato plants in the field, the major verticillium wi lt pathogens present in field soils can be rapidly and reliably detected by the PCR assay.