Clubroot resistance derived from the European Brassica napus cv. ‘Tosca’ is not effective against virulent Plasmodiophora brassicae isolates from Alberta, Canada

Abstract

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.

Production of Clubroot Standards Using a Recombinant Surrogate to Overcome Natural Genetic Variability

“…Virulent pathotypes of P. brassicae capable of overcoming resistance have emerged in Alberta. However, relatively little attention has been given to the analysis of clubroot populations in soil used to characterise clubroot variation in differential set responses [33].…”

No rest for resting spores: Can predators mitigate clubroot disease?

“…With a production of more than 24 million tons, Brassica napus (also called canola or oilseed rape) is the second most important oilseed crop globally (FAOSTAT, 2019). Its intensive cultivation has led to an increase of many Brassica diseases including the soil‐borne clubroot disease (Fredua‐Agyeman et al, 2021; Zheng et al, 2020).…”

“…One often applied strategy to minimise the impact of clubroot is the use of resistant crop host cultivars (Javed et al, 2023). But high concentrations of the pathogen in the soil can overcome plant resistance (Ernst et al, 2019) and the emergence of isolates able to counteract plant resistance is a major issue (Ernst et al, 2019; Fredua‐Agyeman et al, 2021; Strelkov et al, 2016). Furthermore, there are different pathotypes of P. brassicae , which can be present simultaneously in the same field or even in a single host plant (Fahling et al, 2003), and plant resistance is often pathotype‐specific (Fredua‐Agyeman et al, 2021).…”

“…But high concentrations of the pathogen in the soil can overcome plant resistance (Ernst et al, 2019) and the emergence of isolates able to counteract plant resistance is a major issue (Ernst et al, 2019; Fredua‐Agyeman et al, 2021; Strelkov et al, 2016). Furthermore, there are different pathotypes of P. brassicae , which can be present simultaneously in the same field or even in a single host plant (Fahling et al, 2003), and plant resistance is often pathotype‐specific (Fredua‐Agyeman et al, 2021). Thus, the efficiency of using resistant crops depends on the specific P. brassicae pathotypes and pathogen concentration in the soil.…”

“…brassicae, which can be present simultaneously in the same field or even in a single host plant (Fahling et al, 2003), and plant resistance is often pathotype-specific (Fredua-Agyeman et al, 2021). Thus, the efficiency of using resistant crops depends on the specific P. brassicae pathotypes and pathogen concentration in the soil.…”