Accumulation of quantitative trait loci conferring broad-spectrum clubroot resistance in Brassica oleracea
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Accumulation of quantitative trait loci conferring broadspectrum clubroot resistance in Brassica oleracea Hiroya Tomita • Motoki Shimizu • Md. Asad-ud Doullah • Ryo Fujimoto Keiichi Okazaki
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Received: 19 March 2013 / Accepted: 2 July 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract Throughout the world, clubroot disease is one of the most damaging diseases affecting Brassica oleracea. To develop marker-assisted selection (MAS) that could assist the incorporation of durable clubroot resistance (CR) into cultivars, previous genetic analyses have identified several CR quantitative trait loci (CR–QTL). However, the independent and cumulative effects of each CR locus against various isolates have rarely been tested. Previously, we identified one major CR–QTL and four minor CR–QTL in the F2 plants from broccoli doubled haploid (DH) line 9 cabbage DH line of B. oleracea. In the present study, to clarify their effectiveness for controlling disease involving various isolates, inoculation testing was conducted in genotypes with various combinations of the CR genes, which were selected using the DNA markers closely associated with each CR–QTL. In exploring the overall disease incidence, it was apparent that a single involvement of the major Electronic supplementary material The online version of this article (doi:10.1007/s11032-013-9918-9) contains supplementary material, which is available to authorized users. H. Tomita M. Shimizu Md. Asad-ud Doullah R. Fujimoto K. Okazaki (&) Graduate School of Science and Technology, Niigata University, Niigata, Japan e-mail: [email protected] Md. Asad-ud Doullah Faculty of Agriculture, Sylhet Agricultural University (SAU), Sylhet, Bangladesh
CR gene located in the PbBo(Anju)1 locus, or accumulation of CR genes in the minor CR–QTL, is not enough to confer sufficient resistance. One major CR gene in the QTL PbBo(Anju)1 locus plus two to three minor CR genes conferred moderate resistance. The genotype in which all of the CR genes locating in the five QTL including PbBo(Anju)1 were accumulated showed the highest resistance, and it was broadly resistant against six isolates. Accumulation of several CR genes by MAS is necessary to conduct CR breeding in B. oleracea. Our developed DNA markers can be used efficiently to make selections of required loci for the acquisition of resistance, and use of these markers will be a powerful tool for CR breeding in B. oleracea. Keywords Brassica oleracea Clubroot resistance MAS (marker-assisted selection) Plasmodiophora brassicae QTL (quantitative trait locus)
Introduction Clubroot disease, caused by a soil-borne obligate biotroph, Plasmodiophora brassicae, is the most destructive disease in Brassica crops (Dixon 2009a). Nutrient absorption and growth in infected plants are inhibited by the formation of clubs on roots which, in the end, leads to substantial decrease in crop quality and yield. Resting spores are released into soil by the decay of infected plants, and they can survive for
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