Assessment of the impact of resistant and susceptible canola on <i>Plasmodiophora brassicae</i> inoculum potential

Hwang, Sheau‐Fang; Ahmed, Hammad; Zhou, Qixing; Strelkov, Stephen E.; Gossen, B. D.; Peng, Gary; Turnbull, G. D.

doi:10.1111/j.1365-3059.2011.02582.x

Cited by 46 publications

(19 citation statements)

References 24 publications

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“…In fields with P. brassicae infestations, the clubroot severity observed in plant stands seeded with CR canola was very low (ID rarely >10% and generally <4.15%). These mild symptoms of clubroot even in the presence of relatively high levels of P. brassicae inoculum probably reflected the fact that this study was focused on CR canola, which would not be expected to develop much disease (Hwang et al ., ). Nevertheless, greater initial concentrations of inoculum did result in slightly higher levels of disease in CR canola crops.…”

Section: Discussionmentioning

confidence: 97%

Plasmodiophora brassicae resting spore dynamics in clubroot resistant canola (Brassica napus) cropping systems

Ernst

Kher²,

Stanton

et al. 2018

Plant Pathology

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The soilborne pathogen Plasmodiophora brassicae, causal agent of clubroot of canola (Brassica napus), is difficult to manage due to the longevity of its resting spores, ability to produce large amounts of inoculum, and the lack of effective fungicides. The cropping of clubroot resistant (CR) canola cultivars is one of the few effective strategies for clubroot management. This study evaluated the impact of the cultivation of CR canola on P. brassicae resting spore concentrations in commercial cropping systems in Alberta, Canada. Soil was sampled pre‐seeding and post‐harvest at multiple georeferenced locations within 17 P. brassicae‐infested fields over periods of up to 4 years in length. Resting spore concentrations were measured by quantitative PCR analysis, with a subset of samples also evaluated in greenhouse bioassays with a susceptible host. The cultivation of CR canola in soil with quantifiable levels of P. brassicae DNA resulted in increased inoculum loads. There was a notable lag in the release of inoculum after harvest, and quantifiable P. brassicae inoculum peaked in the year following cultivation of CR canola. Rotations that included a ≥2‐year break from P. brassicae hosts resulted in significant declines in soil resting spore concentrations. A strong positive relationship was found between the bioassays and qPCR‐based estimates of soil infestation. Results suggest that CR canola should not be used to reduce soil inoculum loads, and crop rotations in P. brassicae infested fields should include breaks of at least 2 years away from B. napus, otherwise the risk of selecting for virulent pathotypes may increase.

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Section: Discussionmentioning

confidence: 97%

Plasmodiophora brassicae resting spore dynamics in clubroot resistant canola (Brassica napus) cropping systems

Ernst

Kher²,

Stanton

et al. 2018

Plant Pathology

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“…(), where the concentration of resting spores in the soil was an essential factor in the subsequent development of a clubroot epidemic. Similarly, repeated cropping of susceptible OSR over 4‐ and 6‐week cycles increased clubroot severity over time (Hwang et al ., ). Another interesting finding in this study is that a few of the spores obtained from 7 dpi‐roots were mature enough to infect new host plants.…”

Section: Discussionmentioning

confidence: 97%

“…The study of Hwang et al . () showed that the pathogen could produce up to 10 10 resting spores⁄g gall under field conditions. They found that repeated growing of susceptible OSR resulted in greater gall fresh weight and favoured the rapid build‐up of resting spores in the soil.…”

Section: Introductionmentioning

confidence: 99%

Reducing the build‐up of Plasmodiophora brassicae inoculum by early management of oilseed rape volunteers

Zamani-Noor

Rodemann

2017

Plant Pathology

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Clubroot of oilseed rape (OSR), caused by Plasmodiophora brassicae, is a disease of increasing economic importance worldwide. Previous studies indicated that OSR volunteers, Brassica crops and weeds play a critical role in the predisposition of the disease. To determine the effect of timing of foliar application of the herbicide glyphosate or mechanical destruction of OSR volunteers in reduction of clubroot severity and resting spore production, a series of studies was conducted under controlled conditions with a susceptible OSR cultivar and an isolate of P. brassicae. Plants were inoculated by injecting a spore suspension beside the root hairs at growth stage 11–12 (BBCH scale) and were terminated at 7 (early) or 21 (late) days post‐inoculation (dpi). Under controlled conditions, the first symptoms on roots were observed as early as 7 dpi. The early application of glyphosate as well as early mechanical destruction resulted in significant (P ≤ 0.05) reduction in the development of clubroot symptoms, root fresh weight and the number of resting spores⁄g root. Furthermore, the effect of volunteer management on clubroot severity in the succeeding OSR was studied by inoculating plants with the resting spores obtained from treated clubbed roots. Inoculated OSR exhibited root clubs similar to the initial symptoms after 35 dpi. Plants that were inoculated with spore suspension from early treated roots resulted in significant reductions in clubroot incidence and severity. Conversely, plants inoculated with the spore suspension from the late treated roots displayed levels of clubroot similar to the plants inoculated with the spore solutions of positive controls.

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“…However, there were no consistent differences among the resistant cultivars for RHI, and cultivar × isolate interactions for the incidence of the developmental stages of RHI were very small, which indicates that all of these resistant cultivars reacted in the same way to all of the isolates assessed. This supports the results of two recent studies that demonstrated the initial levels of RHI were higher in a susceptible canola cultivar than in ‘45H29’, which was the first clubroot‐resistant canola cultivar registered in Canada (Deora et al ., ; Hwang et al ., ). In the moderately resistant cv.…”

Section: Discussionmentioning

confidence: 97%

“…brassicae (root hair infection) occurs in both susceptible and resistant cultivars of host species, and even in non‐host crops (Ludwig‐Müller et al ., ; Deora et al ., ; Feng et al ., ). However, the infection success and rate of pathogen development in roots hairs differ slightly among canola cultivars, with development occurring quickly in susceptible lines, more slowly in highly resistant lines, and slower still in cultivars with intermediate resistance (Deora et al ., ; Hwang et al ., ). Clubroot resistance is expressed most clearly and consistently in the root cortex, where pathogen development occurred quickly in susceptible cultivars, more slowly in cultivars with intermediate resistance, and there is little or no pathogen development in highly resistant cultivars (Kroll et al ., ; Deora et al ., ).…”

Section: Introductionmentioning

confidence: 97%

Cytology of infection, development and expression of resistance to Plasmodiophora brassicae in canola

Deora

Gossen

McDonald

2013

Annals of Applied Biology

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The timing and expression of resistance to four isolates of Plasmodiophora brassicae, collected from research sites where pathotypes 2, 3, 5 and 6 (Williams' system) had been dominant when characterised in 2006, were assessed in four new commercial cultivars of canola (Brassica napus) with resistance to clubroot. Each of the resistant cultivars was highly resistant to all four of the isolates, and there was no difference in their response to infection. Root hair infection occurred at high levels, but pathogen development occurred more slowly than in a susceptible cultivar (control). Secondary infection and development in cortical cells was severely inhibited in each of the resistant cultivars; only a few bi-nucleated plasmodia were observed at 12 days after inoculation (DAI), and plasmodia were rarely observed at 18 and 24 DAI. In contrast, development in the susceptible cultivar had progressed to resting spores by 24 DAI. A dense ring of accumulated reactive oxygen species (ROS) was observed in the endodermis, pericycle and vascular cambium of noninoculated controls and inoculated plants of the resistant cultivars. However, the ROS ring disappeared rapidly in infected plants of the susceptible cultivar. Plasmodia invaded the stele of susceptible roots by preferentially colonising the xylem parenchyma cells. Expansion and enlargement of lignified xylem cells was observed by 35 DAI. The absence of any specific points of ROS accumulation or lignification of epidermal or cortical cells in the resistant cultivars indicates that a hypersensitive response is not the main mechanism of resistance in these lines. The uniform response of these resistant cultivars to the four isolates of P. brassicae indicates that the resistance in each cultivar may be conditioned by a gene(s) from a single source that confers broad resistance, because most sources of resistance to P. brassicae are pathotype specific.

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Assessment of the impact of resistant and susceptible canola on Plasmodiophora brassicae inoculum potential

Cited by 46 publications

References 24 publications

Plasmodiophora brassicae resting spore dynamics in clubroot resistant canola (Brassica napus) cropping systems

Plasmodiophora brassicae resting spore dynamics in clubroot resistant canola (Brassica napus) cropping systems

Reducing the build‐up of Plasmodiophora brassicae inoculum by early management of oilseed rape volunteers

Cytology of infection, development and expression of resistance to Plasmodiophora brassicae in canola

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