Verticillium dahliae and Verticillium nonalfalfae occurrence and abundance in several agricultural fields from Nova Scotia, Canada, assessed by real-time quantitative PCR

Verticillium dahliae and Verticillium nonalfalfae are soil-borne fungal pathogens with a ubiquitous geographical distribution affecting a wide range of plants of economic importance. Though Verticillium wilt represents a major problem for crop production in Nova Scotia, Canada, little is known about the distribution of these pathogens in the major agricultural areas from this province. To address the paucity of available data, a molecular-based survey of these Verticillium pathogens, documenting their distribution, incidence, and in-sample abundance, was carried out for two successive years, in several representative agricultural locations in this province. Soil and plant samples (potato and strawberry) were analyzed using real-time quantitative PCR targeting the Intergenic Spacer ribosomal DNA locus of the Verticillium pathogens. Molecular data revealed that V. dahliae has a wider distribution and a higher incidence than V. nonalfalfae (former V. albo-atrum group 1) in the tested fields while V. albo-atrum sensu stricto (former V. albo-atrum group 2) was not identified in any of the samples collected from this region. Also, V. dahliae was found to have a higher incidence in fields used to grow potatoes as compared to fields used to grow strawberries, irrespective of the rotating crops.