Identification and Mapping of the Clubroot Resistance Gene CRd in Chinese Cabbage (Brassica rapa ssp. pekinensis)

Abstract

The rapid spread of clubroot disease, which is caused by Plasmodiophora brassicae, threatens Brassicaceae crop production worldwide. Breeding plants that have broad-spectrum disease resistance is one of the best ways to prevent clubroot. In the present study, eight Chinese cabbage germplasms were screened using published clubroot-resistant (CR) loci-/gene-linked markers. A CR gene Crr3 potential carrier “85-74” was detected which linked to marker BRSTS61; however, “85-74” shows different responses to local pathogens “LAB-19,” “LNND-2,” and “LAB-10” from “CR-73” which harbors Crr3. We used a next-generation sequencing-based bulked segregant analysis approach combined with genetic mapping to detect CR genes in an F2 segregant population generated from a cross between the Chinese cabbage inbred lines “85-74” (CR) and “BJN3-1” (clubroot susceptible). The “85-74” line showed resistance to a local pathogen “LAB-19” which was identified as race 4; a genetic analysis revealed that the resistance was conferred by a single dominant gene. The CR gene which we named CRd was mapped to a 60 kb (1 cM) region between markers yau389 and yau376 on chromosome A03. CRd is located upstream of Crr3 which was confirmed based on the physical positions of Crr3 linked markers. The identification of CRd linked markers can be applied to marker-assisted selection in the breeding of new CR cultivars of Chinese cabbage and other Brassica crops.

Transcriptome Arofile of Brassica rapa L. Reveals the Involvement of Jasmonic Acid, Ethylene, and Brassinosteroid Signaling Pathways in Clubroot Resistance

“…Clubroot disease jeopardizes crop cultivation and yield by causing the development of large galls on the roots that reduce the plant's ability to absorb water and nutrients from the soil. Although clubroot resistance (CR) genes have been identified, mainly in Brassica rapa [16][17][18][19][20][21][22][23], the detailed mechanism of CR remains unclear. However, the suppression of clubroot by exogenous SA was also reported in broccoli (Brassica oleracea) [24].…”

“…It was also shown that Botrytis cinerea regulates both pathways to enable infection of tomato [26]. A novel CR gene (CRd) conferring complete resistance to a specific pathotype of P. brassicae was recently identified in B. rapa [23]. However, the mechanism of action of the CRd gene product and its association with phytohormone signaling at different developmental stages of P. brassicae has yet to be elucidated, and we suspect that the hormonal signal transduction pathway involved in clubroot disease resistance may be distinct due to the different CR genes.…”

“…P. brassicae is an obligate biotrophic pathogen, and it is unclear that the mechanism of SA, JA, and other hormone signal pathways participating in clubroot resistance was different when avirulent and virulent pathotype of P. brassicae infected CR plants at different development stages. In this study, a Chinese cabbage inbred line harboring the CRd gene [23] was inoculated with either an avirulent or virulent pathotype of P. brassicae to investigate the involvement of plant hormone signaling in CR and identify relevant genes by whole-genome transcriptional analysis.…”

An update on the arsenal: mining resistance genes for disease management of Brassica crops in the genomic era

“…Huang et al 149 adopted KASP markers and BSR-seq strategies to finely map Rcr2 to a 0.4 cM interval, identifying two TIR-NBS-LRRs as candidates. Using BSA-seq, Pang et al 150 identified the new locus CRd in a 60 kb region on chromosome A03, which is located upstream of Crr3.…”

Genome-wide identification and expression analysis of the cytokinin gene family in Brassica oleracea L. reveals its role in clubroot resistance

“…The secondary resting zoospores in turn infect cortical cells and form secondary plasmodia, which are the key cause of swollen roots (Rolfe et al 2016). The clubroot hinders the absorption and transport of water and nutrients in plants (Pang et al 2018), causing crop yield reduction.…”