Emergence of new virulence phenotypes of Plasmodiophora brassicae on canola (Brassica napus) in Alberta, Canada

Strelkov, Stephen E.; Hwang, Sheau‐Fang; Manolii, Victor P.; Cao, Tiesen; Feindel, David

doi:10.1007/s10658-016-0888-8

Cited by 128 publications

(136 citation statements)

References 31 publications

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“…Surveys for clubroot were conducted in Alberta in 2013 and 2014, and root galls were collected from fields that had been sown to CR canola cultivars, but which had higher levels of clubroot than expected for varieties with resistance to this disease (Strelkov et al, 2015(Strelkov et al, , 2016b. Based on the reactions of these 16 populations on the differentials of Williams (1966), the populations were designated as pathotypes 2, 3, 5, 6 or 8.…”

Section: Plasmodiophora Brassicae Strains Used For Inoculation Experimentioning

confidence: 99%

Virulence and inoculum density‐dependent interactions between clubroot resistant canola (Brassica napus) and Plasmodiophora brassicae

Hwang¹,

Strelkov

Ahmed³

et al. 2017

Plant Pathology

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To mitigate the impact and dissemination of clubroot in western Canada, canola (Brassica napus) producers have relied on clubroot resistance traits. However, in 2013 and 2014, new strains of the clubroot pathogen, Plasmodiophora brassicae, emerged that are virulent on most clubroot‐resistant (CR) canola genotypes. Novel strains of the pathogen were inoculated onto two susceptible canola cultivars, one resistant line and six CR cultivars. Although all cultivars/lines showed a susceptible response to inoculation with the new strains of P. brassicae, the severity of disease reaction, root hair infection rates and the amount of P. brassicae DNA present in each canola genotype varied depending on the strain. In addition, the effect of inoculum density on disease severity and gall formation was recorded for one of these new strains on a universally susceptible Chinese cabbage cultivar and one susceptible and 10 resistant canola genotypes. Although root galls were observed at an inoculum density of 103 spores per mL of soil, clear differentiation of susceptible and resistant reactions among canola cultivars/lines was not observed until the inoculum density reached 105 spores mL−1. At a spore density of 106 spores mL−1 and above, all cultivars/lines developed susceptible reactions, although there was some differentiation in the degree of reaction. This study shows the potential to develop a unique disease profile for emergent clubroot pathotypes and shows a useful range of spore densities at which to study new P. brassicae strains.

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Section: Plasmodiophora Brassicae Strains Used For Inoculation Experimentioning

confidence: 99%

Virulence and inoculum density‐dependent interactions between clubroot resistant canola (Brassica napus) and Plasmodiophora brassicae

Hwang¹,

Strelkov

Ahmed³

et al. 2017

Plant Pathology

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“…A loss in the effectiveness of resistance, as a result of the selection pressure imposed on pathogen populations by resistant cultivars, was reported a few years after the introduction of blackleg‐resistant oilseed rape cultivars in France (Brun et al ., ; Rouxel et al ., ) and Australia (Li et al ., ; Sprague et al ., ). This may be the case in Alberta, where P. brassicae strains able to overcome resistance were reported 3–4 years after the release of the first clubroot‐resistant canola cultivars in 2009 and 2010 (Strelkov et al ., ).…”

Section: Introductionmentioning

confidence: 99%

“…The release of host cultivars with clubroot resistance represented a major advance in efforts to manage this disease. However, new virulent P. brassicae strains were discovered in Alberta in 2013 to which none of the current clubroot-resistant commercial canola cultivars have any resistance (Strelkov et al, 2016a). Thus, yield losses due to clubroot could be much higher.…”

Section: Introductionmentioning

confidence: 99%

Potential loss of clubroot resistance genes from donor parent Brassica rapa subsp. rapifera (ECD 04) during doubled haploid production

et al. 2018

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Clubroot resistance derived from the oilseed rape/canola Brassica napus ‘Mendel’ has been overcome in some fields in Alberta, Canada, by the emergence of ‘new’ strains of the protist Plasmodiophora brassicae. Resistance to the pathogen was assessed in 112 doubled haploid (DH) lines, derived from B. rapa subsp. rapifera (European clubroot differential (ECD) 04). The lines were evaluated against five single‐spore isolates representing the ‘old’ pathotypes 2, 3, 5, 6 and 8, and 15 field populations representing new strains of P. brassicae. The disease severity index (ID%) data revealed that none of the DH lines were resistant or moderately resistant to the new pathotype 5X (field populations L‐G1, L‐G2, L‐G3) and D‐G3, while 3–42% were resistant or moderately resistant to the other 11 new strains. Using the mean ID induced by the old pathotype 3 (approx. 13.5%) as the baseline, clubroot severity increased by 300–600% when inoculated with the new pathotypes. A significant finding of this study was the fact that ECD 04 showed absolute resistance to all of the old and new P. brassicae strains while the B. napus ‘Mendel’, although resistant to all of the old pathotypes, was resistant to only about 50% of the new strains. Similarly, all of the selected clubroot‐resistant commercial canola cultivars evaluated in this study were susceptible to 87% of the new P. brassicae strains. The molecular data revealed that the breakdown of clubroot resistance in Mendel and the canola cultivars was in part due to the non‐inheritance of the Crr1 gene on the A08 chromosome from ECD 04.

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“…Clubroot has been reported in more than 60 countries or regions around the world, and, in recent years, the disease has become increasingly serious. In Europe, North America, East Asia, and other regions, clubroot has become a major threat (Dixon, 2009; Chittem et al, 2014; Galdames et al, 2014; Strehlow et al, 2014; Wallenhammar et al, 2014; Strelkov et al, 2016). …”

Section: Introductionmentioning

confidence: 99%

Transcriptome Analysis of Arabidopsis thaliana in Response to Plasmodiophora brassicae during Early Infection

Zhao

Gao

et al. 2017

Front. Microbiol.

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Clubroot disease is a serious threat to cruciferous plants worldwide, especially to oilseed rape. However, knowledge on pathogenic molecular mechanisms and host interaction is limited. We presume that the recognition between Arabidopsis thaliana and Plasmodiophora brassicae occurs at the early stage of infection and within a relatively short period. In this study, we demonstrated changes on gene expression and pathways in A. thaliana during early infection with P. brassicae using transcriptome analysis. We identified 1,903 and 1,359 DEGs at 24 and 48 h post-inoculation (hpi), respectively. Flavonoids and the lignin synthesis pathways were enhanced, glucosinolates, terpenoids, and proanthocyanidins accumulated and many hormonal- and receptor-kinase related genes were expressed, caused by P. brassicae infection during its early phase. Therefore, the early interaction between A. thaliana and P. brassicae plays an important role in the entire infection process. The results provide a new contribution to a better understanding of the interaction between host plants and P. brassicae, as well as the development of future measures for the prevention of clubroot.

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Emergence of new virulence phenotypes of Plasmodiophora brassicae on canola (Brassica napus) in Alberta, Canada

Cited by 128 publications

References 31 publications

Virulence and inoculum density‐dependent interactions between clubroot resistant canola (Brassica napus) and Plasmodiophora brassicae

Virulence and inoculum density‐dependent interactions between clubroot resistant canola (Brassica napus) and Plasmodiophora brassicae

Potential loss of clubroot resistance genes from donor parent Brassica rapa subsp. rapifera (ECD 04) during doubled haploid production

Transcriptome Analysis of Arabidopsis thaliana in Response to Plasmodiophora brassicae during Early Infection

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