Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.)

Wallenhammar, Ann-Charlotte; Omer, Zahra Saad; Edin, Eva; Jonsson, Anders

doi:10.3390/pathogens10040433

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Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.)

¹

Rural Economy and Agricultural Society, HS Konsult AB, Gamla vägen 5G, SE-702 22 Örebro, Sweden

²

Rural Economy and Agricultural Society, HS Konsult AB, P.O. Box 412, SE-751 06 Uppsala, Sweden

³

Rural Economy and Agricultural Society, HS Konsult AB, Brunnby Gård, SE-725 97 Västerås, Sweden

⁴

RISE, Research Institutes of Sweden AB, Box 187, SE-532 32 Skara, Sweden

^*

Author to whom correspondence should be addressed.

Pathogens 2021, 10(4), 433; https://doi.org/10.3390/pathogens10040433

Submission received: 17 March 2021 / Revised: 31 March 2021 / Accepted: 4 April 2021 / Published: 6 April 2021

(This article belongs to the Special Issue Epidemiology, Pathogenicity and Management Strategies of Plasmodiophora Brassicae)

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Abstract

Use of resistant cultivars is considered the most effective tool in managing clubroot. Three clubroot-resistant commercial winter oilseed rape (OSR) cultivars and a susceptible ‘Cultivar mix’ were evaluated for disease severity index (DSI) and yield performance in field soils, selected for varying abundance of natural inoculum of Plasmodiophora brassicae. Seven field trials were carried out during 2017–2019 in winter OSR crops, and comparative bioassays were performed in a growth chamber. Substantial variation in clubroot infection between years was observed in the field trials. For Cultivar mix, a negative correlation (y = −252.3ln(x) + 58,897.6) was found between inoculum density and seed yield in five trials, whereas no correlation was found for the resistant cultivars. In bioassays, Cultivar mix exhibited a significantly high correlation between DSI_b and number of gene copies g⁻¹ soil (R² = 0.72). For resistant cvs., Mentor and Alister, correlation was R² = 0.45 and 0.58, respectively, indicating that resistance was under pressure. In field trials, DSI_f of the resistant cultivars was lower (<27). The recommendation is thus to use clubroot-resistant cultivars of OSR as part of Integrated Pest Management in situations where abundance of P. brassicae DNA exceeds 1300 gene copies g⁻¹ soil.

Keywords: Brassica napus; clubroot; real-time qPCR; soil-borne inoculum; resistant cultivars; field trials; yield; bioassays; disease severity index (DSI)

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MDPI and ACS Style

Wallenhammar, A.-C.; Omer, Z.S.; Edin, E.; Jonsson, A. Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.). Pathogens 2021, 10, 433. https://doi.org/10.3390/pathogens10040433

AMA Style

Wallenhammar A-C, Omer ZS, Edin E, Jonsson A. Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.). Pathogens. 2021; 10(4):433. https://doi.org/10.3390/pathogens10040433

Chicago/Turabian Style

Wallenhammar, Ann-Charlotte, Zahra Saad Omer, Eva Edin, and Anders Jonsson. 2021. "Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.)" Pathogens 10, no. 4: 433. https://doi.org/10.3390/pathogens10040433

APA Style

Wallenhammar, A.-C., Omer, Z. S., Edin, E., & Jonsson, A. (2021). Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.). Pathogens, 10(4), 433. https://doi.org/10.3390/pathogens10040433

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Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.)

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