Increasing abiotic (drought) and biotic (clubroot) resistance in Brassica species (Arabidopsis and Canola) by modifying auxin response

Term: 3 years ending December 2023
Status: Complete
Researcher(s): Jocelyn Ozga, Stephen Strelkov, Guanqun Chen, Sheau-Fang Hwang, University of Alberta   
SaskCanola Investment: $51,750
Total Project Cost: $193,500
Funding Partners: ACPC, NSERC

Grower Benefits

• In Arabidopsis, reduced auxin response in auxin receptor mutants, and expression of PsAFB6 (a pea auxin receptor that does not exist in the Brassica family which also reduced auxin response), were each associated with reduced clubroot disease progression, and it is likely that a threshold level of auxin response reduction is required to reduce P. brassicae-induced disease development. Canola transgenic lines expressing the pea auxin receptor also showed reduced clubroot disease symptoms.

• This study supports the hypothesis that auxin is utilized by the clubroot pathogen in gall development, and that reducing auxin response in the plant is a potential mechanism to suppress clubroot disease progression in plants.

• Further research into methods of repressing auxin signaling at the gall development stage of clubroot disease development would be a promising approach that could limit disease progression and potentially reduce resting spore production.

Project Summary

This project focused on increasing our knowledge on plant host-clubroot pathogen interactions by determining if reducing the ability of the pathogen to use the plant hormone auxin (responsible for cell grow, division and expansion in the plant) would reduce clubroot disease progression, particularly at the gall forming stage. The objectives were to test if expression of the pea auxin receptor PsAFB6 in the Brassica genetic model plant Arabidopsis reduced auxin response, and if so, determine if reduced auxin response was associated with reduced clubroot disease progression. The ability of PsAFB6-expressing canola lines to suppress clubroot disease progression was also tested.

The canola and Arabidopsis transgenic lines expressing the pea auxin receptor showed reduced clubroot disease symptoms compared to their null lines. Overall, the researchers learned that the pea auxin receptor likely functions as an auxin sink in Brassica plants, reducing auxin response in the roots of the transgenic plants, and subsequently, resulting in milder gall symptoms in clubroot-inoculated plants. The data generated in this project supports that reduction in auxin response reduces the progression of clubroot symptoms in Brassica species. This supports the concept that auxin is utilized by the clubroot pathogen in gall development, so reducing auxin response is a potential mechanism to suppress clubroot progression in plants in future varieties.