Development of simple sequence repeat markers for the classification of the clubroot pathogen Plasmodiophora brassicae

Clubroot, caused by Plasmodiophora brassicae Woronin, is a significant threat to the canola (Brassica napus L.) industry in Canada. Clubroot resistance has been overcome in more than 200 fields since 2013, representing one of the biggest challenges to sustainable canola production. The genetic structure of 36 single-spore isolates derived from 12 field isolates of P. brassicae collected before and after the introduction of clubroot resistant (CR) canola cultivars (2005-2014) was evaluated by simple sequence repeat (SSR) marker analysis. Polymorphisms were detected in 32 loci with the identification of 93 distinct alleles. A low level of genetic diversity was found among the single-spore isolates. Haploid linkage disequilibrium and number of migrants suggested that recombination and migration were rare or almost absent in the tested P. brassicae population. A relatively clear relationship was found between the genetic structure and virulence phenotypes of the pathogen as defined on the differential hosts of Somé et al., Williams and the Canadian Clubroot Differential (CCD) set. Although genetic variability within each pathotype group, as classified on each differential system, was low, significant genetic differentiation was observed among the pathotypes. The highest correlation between genetic structure and virulence was found among matrices produced with genetic data and the hosts of the CCD set, with a threshold index of disease of 50% to distinguish susceptible from resistant reactions. Genetically homogeneous single-spore isolates provided a more complete and clearer picture of the population genetic structure of P. brassicae, and the results suggest some promise for the development of pathotype-specific primers.

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Classification of “nabana” (<i>Brassica rapa</i>) cultivars and landraces based on simple sequence repeat markers

Kubo

Onnazaka²,

Mizuno

et al. 2019

Breed. Sci.

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Brassica rapa or B. napus vegetables for eating as young inflorescences and stalks are called “nabana”. Japanese nabana includes “flower-bud type” and “stem-and-leaf type”. Chinese and European types are also known (cai-xin, zicaitai, and broccoletto). We classified nabana belonging to B. rapa and other B. rapa vegetables. In a simple sequence repeat-based phylogram, 49 ingroup samples were classified into four groups (I–IV). Flower-bud and stem-and-leaf types were separated into groups I and III, respectively, with a slight overlap in group II. Cai-xin and non-heading Chinese cabbages were included in group IV. Broccoletto was placed in group III, close to turnips. Zicaitai cultivars were included in group II. We tested for clubroot resistance (CR) and its marker genotypes in nabana because of their agronomical importance. Ten cultivars were resistant to group 4 pathogen but not to group 2. Most of the CR cultivars had heterozygous resistance alleles in the CRb and Crr1 loci, consistent with inoculation tests. Our results suggest that Japanese nabana lines and foreign types were differentiated according to their consumption parts and cultivar origins, respectively. This study elucidates the relationships and CR properties of nabana and provides valuable information for the breeding of nabana cultivars.

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Development of simple sequence repeat markers for the classification of the clubroot pathogen Plasmodiophora brassicae

Cited by 4 publications

References 16 publications

Genetic variation analysis of field isolates of clubroot and their responses to Brassica napus lines containing resistant genes CRb and PbBa8.1 and their combination in homozygous and heterozygous state

Genetic variation analysis of field isolates of clubroot and their responses to Brassica napus lines containing resistant genes CRb and PbBa8.1 and their combination in homozygous and heterozygous state

Genetic Structure ofPlasmodiophora brassicaePopulations Virulent on Clubroot Resistant Canola (Brassica napus)

Classification of “nabana” (<i>Brassica rapa</i>) cultivars and landraces based on simple sequence repeat markers

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