Movement of Plasmodiophora brassicae resting spores in windblown dust

Clubroot (Plasmodiophora brassicae Wor.) of canola (Brassica napus L.) was first detected in Alberta, Canada, near Edmonton in 2003. Since that time it has become a severe problem in canola production, spreading throughout central Alberta, with isolated cases of the disease also identified in southern Alberta, Saskatchewan and Manitoba. Clubroot is believed to be spreading mostly via the movement of P. brassicae-infested soil on farm machinery. This study examined the potential for the spread of the pathogen in windblown dust from infested fields. Dust samplers were placed at four locations, three in central Alberta and one in southern Alberta, in 2011 and 2012. Soil particles in suspension and moving through saltation were collected in samplers at heights ranging from 0 to 1 m. Total genomic DNA was extracted from the collected soil samples and subjected to conventional polymerase chain reaction (PCR) and quantitative PCR analysis for the detection and quantification of P. brassicae in the samples. The DNA of P. brassicae was detected in samplers at all locations in both years. There was no clear association between sampling height and the frequency of samples testing positive for the presence of P. brassicae DNA, or between sampling height and the amount of P. brassicae DNA. The results indicate that P. brassicae resting spores can be carried by wind-borne dust and that wind-mediated dispersal likely contributes to spread of this pathogen.