Molecular characterization of the CRa gene conferring clubroot resistance in Brassica rapa.
ABSTRACT Clubroot disease is one of the major diseases affecting Brassicaceae crops, and a number of these crops grown commercially, such as Chinese cabbage (Brassica rapa L. ssp. pekinensis), are known to be highly susceptible to clubroot disease. To provide protection from this disease, plant breeders have introduced genes for resistance to clubroot from the European turnip into susceptible lines. The CRa gene confers specific resistance to the clubroot pathogen Plasmodiophora brassicae isolate M85. Fine mapping of the CRa locus using synteny to the Arabidopsis thaliana genome and partial genome sequences of B. rapa revealed a candidate gene encoding a TIR-NBS-LRR protein. Several structural differences in this candidate gene were found between susceptible and resistant lines, and CRa expression was observed only in the resistant line. Four mutant lines lacking clubroot resistance were obtained by the UV irradiation of pollen from a resistant line, and all of these mutant lines carried independent mutations in the candidate TIR-NBS-LRR gene. This genetic and molecular evidence strongly suggests that the identified gene is CRa. This is the first report on the molecular characterization of a clubroot Resistance gene in Brassicaceae and of the disease resistance gene in B. rapa.
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ABSTRACT: Clubroot disease caused by Plasmodiophora brassicae Woronin is a concern to the canola (Brassica napus L.) growers in Canada. A crop management strategy that includes deployment of genetic resistance and appropriate cultural practices is needed for long-term management of this disease. Resistance to the P. brassicae pathotypes present in Canada has been found in the primary and secondary gene pools of spring B. napus canola. Some of these sources, such as winter canola 'Mendel', rutabaga and Pak Choi (Brassica rapa L.) 'Flower Nabana', were used in genetic studies and breeding for the development of clubroot-resistant canola cultivars. A dominant gene in 'Mendel' and 'Flower Nabana' was found to confer resistance to P. brassicae pathotype 3, while a simple or a complex genetic control of resistance was found in rutabaga. The clubroot resistance (CR) gene in 'Flower Nabana' was mapped to chromosome A3, and molecular markers linked to the CR gene were identified for use in marker-assisted breeding (MAB). Using the CR genes from 'Mendel' and rutabaga, several clubroot-resistant spring canola lines were developed. Often the CR genes of 'Mendel' and rutabaga conferring resistance to pathotype 3 also conferred resistance to other pathotypes of P. brassicae found in Canada, including pathotypes 5, 6 and 8. The CR gene of 'Flower Nabana' was introgressed into B. napus and B. rapa canola through MAB. Since single-gene controlled resistance can be eroded, other strategies such as pyramiding different CR genes into B. napus canola should be considered for durable resistance.Canadian Journal of Plant Pathology 03/2014; 36(sup1):122-134. DOI:10.1080/07060661.2013.862571 · 0.99 Impact Factor
Horticulture, Environment and Biotechnology 12/2014; 55(6):540-547. DOI:10.1007/s13580-014-0079-5 · 0.49 Impact Factor
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ABSTRACT: Clubroot resistance (CR) is an important trait for Chinese cabbage (Brassca rapa L. ssp. pekinensis). Since no CR genes had been found throughout Chinese cabbage lines originally, they were introduced from CR European turnips. Distribution of CR genes in the commercial cultivar is important information for CR breeding, but it has been scarcely known at molecular level. In this work, CR of 47 Chinese cabbage cultivars were analyzed phenotypically and genotypically. More than 80% of them exhibited high resistance phenotype, and all of the cultivars with high resistance were found to have CRa, one of the genes controlling CR. Majority of these cultivars were heterozygote for resistance, which is reasonable because CRa controls the resistance single-dominantly. This is the first work reporting the distribution of CR gene in Chinese cabbage cultivars and provides important and practical information for breeders and farmers. Further applications of CR genes are also discussed.Plant Biotechnology 01/2013; 30(4):393-397. DOI:10.5511/plantbiotechnology.13.0110a · 1.06 Impact Factor