Clubroot resistance derived from the European Brassica napus cv. 'Tosca' is not effective against virulent Plasmodiophora brassicae isolates from Alberta, Canada.
In this study, clubroot resistance in the resynthesized European winter Brassica napus cv. 'Tosca' was introgressed into a Canadian spring canola line '11SR0099', which was then crossed with the clubroot susceptible spring line '12DH0001' to produce F1 seeds. The F1 plants were used to develop a doubled haploid (DH) mapping population. The parents and the DH lines were screened against 'old' pathotypes 2F, 3H, 5I, 6M and 8N of the clubroot pathogen, Plasmodiophora brassicae, as well as against the 'new' pathotypes 5X, 5L, 2B, 3A, 3D, 5G, 8E, 5C, 8J, 5K, 3O and 8P. Genotyping was conducted using a Brassica 15K SNP array. The clubroot screening showed that 'Tosca, '11SR0099' and the resistant DH lines were resistant to three (2F, 3H and 5I) of the five 'old' pathotypes and four (2B, 3O, 8E and 8P) of the 12 'new' pathotypes, while being moderately resistant to the 'old' pathotype 8N and the 'new' pathotypes 3D and 5G. 'Tosca' was susceptible to isolates representing pathotype 3A (the most common among the 'new' pathotypes) as well as pathotypes 6M, 5X, 5L, 5K and 8J. Linkage analysis and QTL mapping identified a ca. 0.88-0.95 Mb genomic region on the A03 chromosome of 'Tosca' as conferring resistance to pathotypes 2F, 3H, 5I, 2B, 3D, 5G, 8E, 3O and 8P. The identified QTL genomic region housed the CRk, Crr3 and CRd gene(s). However, the susceptibility of 'Tosca' to most of the common virulent pathotypes makes it unattractive as a sole CR donor in the breeding of commercial canola varieties in western Canada.
Fredua-Agyeman R
，Hwang SF
，Zhang H
，Falak I
，Huang X
，Strelkov SE
... -
《Scientific Reports》
Identification of a genomic region containing genes involved in resistance to four pathotypes of Plasmodiophora brassicae in Brassica rapa turnip ECD02.
Clubroot, caused by Plasmodiophora brassicae, is an important disease of brassica crops worldwide. Vegetable turnip (Brassica rapa L.) have proven to be a source of clubroot resistance genes effective against many pathotypes of P. brassicae. The F1 progeny from the cross B. rapa canola ACDC (susceptible, S) × B. rapa turnip ECD02 (resistant, R) were backcrossed with ACDC, then self-pollinated to produce BC1 S1 lines. All the F1 plants were resistant to four pathotypes (3A, 3D, 3H, and 5X) of P. brassicae. Segregation for R and S in BC1 to each pathotype was 1:1 and resistance reactions were highly correlated. From whole genome sequencing, 192.1 M sequences with 96% template coverage from ECD02, and 478.9 M sequences with 92% coverage from ACDC, were aligned with the reference genome of B. rapa. Genotyping-by-sequencing was performed on the BC1 population. The number of aligned short reads per plant in the BC1 ranged from 1.4 to 8.5 M sequences with 4-8% template coverage. We obtained 1,344 high-quality single-nucleotide polymorphism (SNP) loci with a mean missing rate at 0.27% and distributed them on 10 chromosomes. A single co-localized quantitative trait loci (QTL), designated as Rcr9ECD02 on chromosome A08, conferred resistance to the four pathotypes. The QTL explained 68.9-74.4% of phenotypic variation with the logarithm of the odds values of 24.3 to 31.1. Bulked segregant analysis was performed, and 14 SNP markers linked to the gene were developed using the Kompetitive Allele Specific PCR. Rcr9ECD02 was mapped into an interval of 2.2 cM, flanked by CF_A08_10664692 and CF_A08_12230973, which spanned 1.51 Mb on the chromosome and included 219 B. rapa genes. Four of these genes (BraA08g012910.3C, BraA08g012920.3C, BraA08g013130.3C, and BraA08g013630.3C) encoded disease resistance proteins.
Rahaman M
，Strelkov SE
，Hu H
，Gossen BD
，Yu F
... -
《Plant Genome》
ResearchGate
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