The hydrolytic products of glucosinolates in brassica crops are bioactive compounds. Some glucosinolate derivatives such as oxazolidine-2-thione from progoitrin in brassica oilseed meal are toxic and detrimental to animals, but some isothiocyanates such as sulforaphane are potent anti-carcinogens that have preventive effects on several human cancers. In most B. rapa, B. napus and B. juncea vegetables and oilseeds, there is no or only trace amount of glucoraphanin that is the precursor to sulforaphane. In this paper, RNA interference (RNAi) of the GSL-ALK gene family was used to down-regulate the expression of GSL-ALK genes in B. napus. The detrimental glucosinolate progoitrin was reduced by 65 %, and the beneficial glucosinolate glucoraphanin was increased to a relatively high concentration (42.6 μmol g(-1) seed) in seeds of B. napus transgenic plants through silencing of the GSL-ALK gene family. Therefore, there is potential application of the new germplasm with reduced detrimental glucosinolates and increased beneficial glucosinolates for producing improved brassica vegetables.

Clubroot disease is devastating to Brassica crop production when susceptible cultivars are planted in infected fields. European turnips are the most resistant sources and their resistance genes have been introduced into other crops such oilseed rape (Brassica napus L.), Chinese cabbage and other Brassica vegetables. The European clubroot differential (ECD) set contains four turnip accessions (ECD1–4). These ECD turnips exhibited high levels of resistance to clubroot when they were tested under controlled environmental conditions with Canadian field isolates. Gene mapping of the clubroot resistance genes in ECD1–4 were performed and three independent dominant resistance loci were identified. Two resistance loci were mapped on chromosome A03 and the third on chromosome A08. Each ECD turnip accession contained two of these three resistance loci. Some resistance loci were homozygous in ECD accessions while others showed heterozygosity based on the segregation of clubroot resistance in 20 BC1 families derived from ECD1 to 4. Molecular markers were developed linked to each clubroot resistance loci for the resistance gene introgression in different germplasm.

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There are various clubroot pathogen (Plasmodiophora brassicae) resistance genes within Brassica species with european turnip (B. rapa ssp. rapifera) being identified as potentially the best source of resistance for the development of clubroot-resistant cultivars in chinese cabbage (B. rapa ssp. pekinensis). To use clubroot resistance genes effectively, it is necessary to map these genes so that molecular markers inside or closely linked to these resistance genes can be developed. Using molecular marker-assisted selection, the clubroot resistance genes can be effectively transferred from cultivar to cultivar and from species to species. In this report, one clubroot resistance locus was mapped on linkage group A3 using five segregating populations developed from five chinese cabbage cultivars, suggesting that all the five cultivars shared the same clubroot resistance locus. Furthermore, one of these five chinese cabbage cultivars was used to develop a large segregating population to fine-map this clubroot resistance locus to a 187-kilobp chromosomal region. Molecular markers that are closely linked to the mapped clubroot resistance locus have been developed that can be used for marker-assisted selection in chinese cabbage and canola/rapeseed (B. rapa and B. napus) breeding programs.

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