Identification of two loci for resistance to clubroot (Plasmodiophora brassicae Woronin) in Brassica rapa L.

Abstract

In an analysis of 114 F(2) individuals from a cross between clubroot-resistant and susceptible lines of Brassica rapa L., 'G004' and 'Hakusai Chukanbohon Nou 7' (A9709), respectively, we identified two loci, Crr1 and Crr2, for clubroot (caused by Plasmodiophora brassicae Woronin) resistance. Each locus segregated independently among the F(2) population, indicating that the loci reside on a different region of chromosomes or on different chromosomes. Genetic analysis showed that each locus had little effect on clubroot resistance by itself, indicating that these two loci are complementary for clubroot resistance. The resistance to clubroot was much stronger when both loci were homozygous for resistant alleles than when they were heterozygous. These results indicate that clubroot resistance in B. rapa is under oligogenic control and at least two loci are necessary for resistance.

Accumulation of Three Clubroot Resistance Genes through Marker-assisted Selection in Chinese Cabbage (Brassica rapa ssp. pekinensis).

“…Respective genes, as a whole, worked complementarily and their coexistence resulted in elevated resistance. This contrasts with the results of Suwabe et al (2003) who found a synergetic effect between 2 CR loci, Crr1 and Crr2; high resistance occurred only when resistance alleles at both loci homozygously coexisted.…”

“…DNA markers for clubroot resistance have been developed in major Brassica crops. Seven major CR loci, CRa, CRb, CRk, CRc, Crr1, Crr2, and Crr3, have been identified for Chinese cabbage using various types of markers (Hirai et al, 2004;Matsumoto et al, 1998;Piao et al, 2004;Sakamoto et al, 2008;Suwabe et al, 2003), though mutual relations among them are somewhat ambiguous, because different resistant materials and pathogenic isolates are employed for detecting the loci. The complexity of the clubroot pathogen in particular makes an exact evaluation of resistance genes difficult.…”

Identification and evaluation of clubroot resistance of radish chromosome using a Brassica napus-Raphanus sativus monosomic addition line

“…In addition, the clubroot resistance of B. rapa was much stronger when the two loci for clubroot resistance (Crr1 and Crr2) were homozygous for resistance alleles compared with when they were heterozygous (Suwabe et al 2003). Because the c-type MAL might be hemizygous for the resistance allele (s), disomic addition lines (DALs, 2n = 40) with a pair of c-chromosomes and homozygous for the resistance allele (s) could also clarify the mechanism of clubroot resistance of radish.…”

“…Moreover, synthetic amphidiploid Raphanobrassica, which was developed by the hybridization of Raphanus and Brassica, also have high levels of clubroot resistance (McNaughton 1973, Yoshikawa 1981. However, the CR gene(s) of radish has not been investigated in comparison with that of Brassica crops such as B. rapa (2n = 20, AA), B. oleracea (2n = 18, CC), and B. napus (Kuginuki et al 1997, Moriguchi et al 1999, Manzanares-Dauleux et al 2000, Suwabe et al 2003, 2006, Hirai et al 2004, Nomura et al 2005. Although QTL analysis was conducted previously by Kamei et al (2007), the clubroot resistance of radish has not been investigated at the chromosomal level.…”

Chinese cabbage (Brassica rapa ssp. pekinensis) – a valuable source of resistance to clubroot (Plasmodiophora brassicae)

“…However, expression of resistance is often quantitative and the genetic basis of the resistance to clubroot in B. rapa is not clear. Moreover, breakdown of disease resistance resulting from genetic variability of the pathogen has been reported (Suwabe et al 2003;Strelkov et al 2016). Previous experience in other countries has shown that genetic resistance can quickly break down, because the pathotype composition can shift rapidly in response to selection pressure.…”