Arabidopsis ecotype screening reveals novel sources of clubroot resistance.

Clubroot, caused by Plasmodiophora brassicae, poses a persistent threat to Brassicaceae crops, particularly in regions where resistant cultivars are under strong selection pressure. To identify new sources of resistance and better understand the underlying genetic mechanisms, we evaluated 60 Arabidopsis thaliana ecotypes against the highly virulent Canadian pathotype 3A. Using stringent phenotyping criteria, pathogen DNA quantification, and survival analysis, we identified eight resistant ecotypes, including two novel sources, Marce-1 and DraII-6. DraII-6 exhibited exceptionally low disease symptoms and a high survival rate. While the clubroot resistant gene RPB1/WeiTsing was detected in many ecotypes, DraII-6 exhibited uniquely high expression of RPB1 at early infection stages, suggesting a possible role in impeding pathogen establishment. However, the observed resistance pattern implies the involvement of additional genetic or regulatory factors beyond RPB1 alone. Given the urgent need to diversify resistance sources and the growing complexity of clubroot epidemiology, we present these findings as a foundation for further mechanistic studies. The rapid release of this work as a Short Communication reflects both its significance for the field and its potential to guide future resistance breeding in Brassica crops.