Specific genes and sequence variation in pathotype 7 of the clubroot pathogen Plasmodiophora brassicae

Abstract

Plasmodiophora brassicae is a biotrophic pathogen and causes clubroot of cruciferous crops. Our study was conducted to find genetic markers for differentiating the pathotype 7. Three molecular markers were obtained, PBRA_000303 presented exclusively in pathotype 7 among the tested pathotypes (P2, P4, P5, P7, P9, P10, P11), PBRA_006533 and PBRA_009559 presented in pathotype 7 and a genotype of pathotype 4 (P4*). The similar results were obtained by clustering analysis based on SRAP and the small subunit (SSU) of P. brassicae rDNA sequence: P7 and P4* were clustered a clade, most of P4 was clustered into another clade. A 380 bp fragment in SSU was existent in P7 and P4* but scarce in most P4. Virulence analysis discovered that pathotype 7 had similar pathogenicity to P4* but lower pathogenicity than most pathotype 4. Although the genetic information had similarity among different pathotype, it is noteworthy that this study is the first to establish a specific molecular identification system for pathotype 7 by PCR analysis, and provides a promising tool to conveniently monitor the distribution of P7.