Introgression of clubroot resistance from B. rapa into B. napus canola and identification of molecular markers for resistance, and pyramiding of this resistance with other resistance genes

Project Summary

Background

Several clubroot-resistant canola cultivars have been developed in Canada since the identification of clubroot disease in canola fields in 2003. However, some of the resistance genes present in these cultivars became ineffective in a short period due to evolution of new Plasmodiophora brassicae pathotypes. Therefore, introgression of additional clubroot resistance genes into canola as well as mapping and characterization of the genes is needed for efficient use of the resistances in breeding.

Results

In this project, resistance to multiple P. brassicae pathotypes including pathotype 3A was introgressed into B. napus canola through interspecific cross between these two species. By using the canola lines derived from the Canola × Turnip cross, four clubroot resistance loci were identified on A02, A03, A08 and A09; these loci confer resistance to pathotype 3A. By using the canola lines derived from the Canola × Chinese cabbage cross, a single locus conferring resistance to pathotype 3H was also identified on chromosome A03. Among these, the clubroot resistance locus of A09 is novel in canola – this locus has not been reported previously.

Conclusions

The clubroot resistance of turnip introgressed into canola plays an important role in resistance to multiple P. brassicae pathotypes including the recently evolved pathotypes 3A, 2B, 3D and 5X. Analysis of the canola lines carrying turnip-resistance also identified several genes and proteins to be involved in clubroot resistance and laid the foundation for functional validation of these genes and proteins.

The knowledge and materials developed from this research can be used in breeding to develop improved clubroot resistant canola cultivars.

Applications

This research generated several canola quality lines with acceptable agronomic and seed quality traits, and exhibiting resistance to multiple P. brassicae pathotypes including the recently evolved pathotype 3A. Mapping of the resistances demonstrated that multiple clubroot resistance loci can be introgressed from B. rapa into canola; among the introgressed loci, the A09 locus is novel in canola.

This project also provided a deeper insight into the putative genes and proteins to be involved in clubroot resistance, and this laid the foundation for functional validation of these genes and proteins. Thus, the knowledge of the genes and proteins, and the novel clubroot resistant germplasm and molecular markers developed from this project can be used in breeding to develop improved clubroot resistant canola cultivars.