Genetic Diversity and Pathogenicity of Cylindrocarpon destructans Isolates Obtained from Korean Panax ginseng

We analyzed the genetic diversity of Cylindrocarpon destructans isolates obtained from Korean ginseng (i.e., Panax ginseng) roots by performing virulence tests and nuclear ribosomal gene internal transcribed spacer (ITS) and mitochondrial small subunit (mt SSU) rDNA sequence analysis. The phylogenetic relationship analysis performed using ITS DNA sequences and isolates from other hosts helped confirm that all the Korean C. destructans isolates belonged to Nectria/Neonectria radicicola complex. The results of in vivo and ex vivo virulence tests showed that the C. destructans isolates could be divided into two groups according to their distinctive difference in virulence and the genetic diversity. The highly virulent Korean isolates in pathogenicity group II (PG II), together with foreign isolates from P. ginseng and P. quinquefolius, formed a single group. The weakly virulent isolates in pathogenicity group I, together with the foreign isolates from other host plants, formed another group and exhibited a greater genetic diversity than the isolates of PG II, as confirmed by the mt SSU rDNA sequence analysis. In addition, as the weakly virulent Korean isolates were genetically very similar to the foreign isolates from other hosts, they were likely to originate from hosts other than the ginseng plants.

Direct Detection of Cylindrocarpon destructans, Root Rot Pathogen of Ginseng by Nested PCR from Soil Samples

We have successfully applied the nested PCR to detect Cylindrocarpon destructans, a major pathogen causing root rot disease from ginseng seedlings in our former study. The PCR assay, in this study, was used to detect the pathogen from soils. The nested PCR using internal transcribed spacer (ITS) 1, 4 primer set and Dest 1, 4 primer set maintained the specificity in soils containing various microorganisms. For a soil DNA extraction method targeting chlamydospores, when several cell wall disrupting methods were tested, the combination of lyophilization and grinding with glass beads, which broke almost all the chlamydospores, was the strongest. The DNA extraction method which was completed based on the above was simple and time-saving because of exclusion of unnecessary stages, and efficient to apply in soils. As three ginseng fields whose histories were known were analyzed, the PCR assay resulted as our expectation derived from the field information. The direct PCR method will be utilized as a reliable and rapid tool for detecting and monitoring C. destructans in ginseng fields.