Fine Mapping a Clubroot Resistance Locus in Chinese Cabbage

Abstract

<jats:p>There are various clubroot pathogen (<jats:italic>Plasmodiophora brassicae</jats:italic>) resistance genes within <jats:italic>Brassica</jats:italic> species with european turnip (<jats:italic>B. rapa</jats:italic> ssp. <jats:italic>rapifera</jats:italic>) being identified as potentially the best source of resistance for the development of clubroot-resistant cultivars in chinese cabbage (<jats:italic>B. rapa</jats:italic> ssp. <jats:italic>pekinensis</jats:italic>). 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 (<jats:italic>B. rapa</jats:italic> and <jats:italic>B. napus</jats:italic>) breeding programs.</jats:p>

Mapping of clubroot (Plasmodiophora brassicae) resistance in canola (Brassica napus)

“…The QTLs PbBa3.1, 3.2 and 3.3 from ECD 04 conferred resistance to pathotypes 2, 10 and 7, respectively (Chen et al ., ). A CR locus (Gao et al ., ) that conferred resistance to a field isolate from Edmonton, Canada, originated from a Chinese cabbage commercial hybrid; however, the resistance of most Chinese cabbage inbred lines originated from turnip (Zhang et al ., ), so it was predicted that this CR locus was also from turnip. In B. napus , QTLs conferring resistance to isolates 01:60, k, 01.07 and 1 were mapped to chromosome N3 (Werner et al ., ).…”

“…The CR locus found in this study is CRa or a CRa‐ linked gene, which could also be aligned to Arabidopsis chromosome 4. Another CR locus confers resistance to a field isolate from Edmonton and was also mapped to the same area at the bottom of N3 (Gao et al ., ), suggesting that they are linked. However, the resistant parent 12‐3 is highly resistant to pathotypes 2, 3, 5, 6 and 8, suggesting a different resistance spectrum from that of CRa , CRb , CRb kato , RCr1 or the CR locus aligned to Arabidopsis chromosome 4.…”

“…Primer pairs for 15 markers that have been linked to CR genes were synthesized and screened between the parents and between the two bulks. The sequences of the primers, as well as the detailed information on the corresponding markers, are listed in Table S1 (Hirai et al ., ; Piao et al ., ; Saito et al ., ; Suwabe et al ., ; Hayashida et al ., ; Sakamoto et al ., ; Ueno et al ., ; Gao et al ., ). Primers specific to the CRa gene were designed based on the sequence of CRa (GenBank accession no.…”

QTL mapping for tuberous stem formation of kohlrabi (Brassica oleracea var. gongylodes L.)

“…The BC1 population showed ample variation for stem swelling trait, and the segregation pattern fits well to a normal continuous distribution which was suitable for a QTL study (Table 1, Supplementary figure 1, Supplementary figure 2). It can be noted that BC1 populations have been used in previously reported genetic analyses for the fine mapping of the club root resistance QTL in Chinese cabbage (Gao et al 2014) and the fine mapping of a major locus controlling plant height in B. napus (Wang et al 2016). Lou et al (2007) also identified QTLs for tuberous root formation using BC1 population in turnip.…”

Introgression of clubroot resistance into an elite pak choi inbred line through marker‐assisted introgression breeding

“…Numerous studies have aimed to improve CR in Chinese cabbage, turnip, rapeseed and lettuce by introgression breeding combined with MAS (Diederichsen and Sacristan 1996, Piao et al 2007, Kutcher et al 2010, Tomita et al 2013, Gao et al 2014, Zhang et al 2015; however, few studies have focused on pak choi. In this study, we aimed to (i) analyse the inheritance of CR in pak choi and develop sequence-characterized amplified region (SCAR) markers that can practically distinguish clubroot-resistant genotypes from susceptible genotypes in a large number of individuals and (ii) improve resistance of pak choi to clubroot by introgression of the CR gene from Chinese cabbage using MAS.…”