Identification and genetic mapping of resistance genes against Canadian pathotypes of Plasmodiophora brassicae in Brassica rapa and Brassica napus

• Author / Creator

  Rahaman, Md Mizanur

• Clubroot (Plasmodiophora brassicae) is an important disease of canola/rapeseed (Brassica napus) and other crucifers. In this study, resistance loci/genes effective against P. brassicae pathotypes 2B, 3A, 3D, 3H, 5C, 5X and 8J were identified and mapped via genotyping-by-sequencing, QTL analysis, conventional linkage mapping, and by exploring the effect of individual genes on quantitative traits in combination with marker and trait data. Four of 34 B. napus accessions, CGN06902, CGN17369, AAFC695, and CN46235, were resistant to pathotypes 3A, 2B, and 3D, while 16 B. rapa families did not show any resistance. The resistant accession AAFC695, B. napus ‘Mendel’ (resistant to 13 of 17 pathotypes identified on the Canadian Clubroot Differential set), and B. rapa line ECD02 (resistant to all 17 pathotypes) were used to map resistance genes by developing a BC1S1 population based on ECD02 and doubled haploid (DH) populations based on ‘AAFC695’ and ‘Mendel’. A single QTL Rcr9ECD02 was identified on chromosome A08 of ECD02 using 93 BC1S1 lines; this QTL conferred resistance to pathotypes 3A, 3D, 3H, and 5X, accounting for 68.9-74.4% phenotypic variation explained (PVE). Bulked segregant and KASP analysis confirmed the QTL. In ‘AAFC695’, a QTL Rcr9AAFC695 was identified on chromosome A08 using 102 DH lines; Rcr9AAFC695 explained 92.6-95.0% PVE in response to pathotypes 3A, 3D, 3H, and 5X, with LOD values of 60.3 to 70.8. In ‘Mendel’, the QTL Rcr3Mendel was mapped on chromosome A08 using 137 DH lines; this was a major locus explaining 88-90% PVE for resistance to pathotypes 3D, 5C, and 8J, with an additive effect of 47.2-47.3%. Testing of 60 lines from this population against pathotype 3H indicated that Rcr3Mendel is the Rcr3 locus, but that it also bestows resistance to pathotypes 3D, 5C, and 8J. The identification of TIRNBSLRR (TNL) genes (via analysis of gene annotation with Blast2GO and gene ontology information) in the QTL regions of the three populations confirmed that the identified QTL Rcr9ECD02, Rcr9AAFC695 and Rcr3Mendel are different from each other, and distinct from Rcr9. The CR loci/genes identified in this study will enrich the repository of resistance genes available to protect canola/rapeseed from clubroot disease.

• Subjects / Keywords

  • Genetic mapping
  • Canola
  • Clubroot
  • Canadian pathotypes

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-43ga-va85

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.