Plasmodiophora brassicae in Mexico, from anecdote to fact

Abstract

For years, the presence of clubroot disease and its causal agent, Plasmodiophora brassicae, in Mexico has been given by granted. However, after a long search in the scientific literature in English and Spanish, as well as grey literature including thesis and government reports, we were not able to find any information regarding the actual detection of the pathogen, hosts affected, areas with the disease, or any real information about clubroot ( hernia de la col, in Mexico). To confirm if P. brassicae was indeed in Mexico, we started a true detective adventure. First, we identified agricultural communities in south-east Mexico known to grow cruciferous crops. Second, we asked to the growers if they have ever seen clubroot symptoms, showing them during the inquires pictures of the characteristic galls that might have been present in their crops. Third, we collected soil from two of the communities with positive response and grew an array of cruciferous in the soil as baits to "fish" the clubroot pathogen. We detected the presence of galls in the roots of 32 plants and observed the presence of resting spores. Through a P. brassicae specific PCR assay, we were able to confirm the presence of the clubroot pathogen in the samples and in Mexico for the very first time. This study is the first report and identification of P. brassicae in Mexico, opening the doors to understand the genetic diversity of this elusive and devastating plant pathogen.