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Whole-genome sequencing showed that the new, virulent pathotypes causing the breakdown in clubroot resistance were almost certainly always present in the pathogen population, and increased rapidly (positive selection) when the first generation of resistance to clubroot was added to canola cultivars.
Project Summary
Objectives of this project were to assess the genetic similarity among populations of Plasmodiophora brassicae from various collections and to examine pathogen variability at various levels, from a single clubbed root, to a field, to a region and then among regions. Researchers collected isolates of P. brassicae from across Canada, including several examples of breakdown of genetic resistance from Alberta and from other sites across Canada, as well as from recent infestations in Saskatchewan, Manitoba and North Dakota. Other collections were obtained from the U.S. and China. In total, more than 80 collections are now available at Saskatoon.
Researchers developed a DNA extraction protocol for P. brassicae suitable for whole genome sequencing. Next-generation sequencing, high-speed computers and specialized software were used to compare the genetic similarity among strains of the pathogen at many spatial levels: field, region, province, country and continent. It showed that the new virulent pathotypes that have been identified in Alberta and across Canada were almost certainly always present in the pathogen population, and so were able to increase as soon as genetic resistance to clubroot was added to canola cultivars.
