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.

Chinese Cabbage Clubroot Pathogen, Plasmodiophora brassicae, Is Genetically Stable

Single spore isolates of Plasmodiophora brassicae e4 and e9 obtained from diseased Chinese cabbage were identified as race 4 and race 9, respectively, by the Williams' differential variety set. To confirm the possibility of variation in same generation and progeny of a single spore isolate of P. brassicae, random amplified polymorphic DNA (RAPD) analysis was conducted using the URP 3, 6 and OPA 7 primers. There was no difference in band type at each part of the gall of Chinese cabbage obtained by inoculation of e4 and e9 and amplification using the URP 3 and 6 primers when the same generation was analyzed. In addition, the progeny analysis, which was expanded to the third generation and conducted using the URP 3 and OPA 7 primers, revealed no differences in the band type of the e4 isolate. Based on these results, the single spore isolate of P. brassicae was genetically stable.

Effect of Isometric Muscle Contraction on the Somatosensory Evoked Potentials

OBJECTIVE: To investigate the association of the muscle contraction with gating of the sensory input at central and peripheral levels according to the intensity of muscle contraction and location of the muscles, somatosensory evoked potentials (SSEPs) studies were evaluated at different levels of isometric contraction in the different muscles. METHOD: Median nerve SSEPs were recorded at Erb's point and scalp in the ten healthy adult subjects with isometric contraction of ipsilateral abductor pollicis brevis (APB), ipsilateral abductor digiti minimi (ADM) and contralateral APB. Median nerve SSEPs were recorded in each of these conditions during precontraction, weak contraction, strong contraction and 4 minutes after contraction. RESULTS: 1) N9 amplitudes of median SSEPs recorded at Erb's point were augumented during weak contraction and these amplitude augumentations were statistically significant in the ipsilateral APB contraction (p<0.05). 2) N20 amplitudes recorded at scalp were inhibited during strong isometric contraction and these amplitude inhibitions were statistically significant in the ipsilateral APB contraction (p<0.05). 3) The latencies of N9 and N20 potentials were not significantly changed during isometric contraction. CONCLUSION: Therefore peripheral nervous system as well as central nervous system is responsible for gating, so the subject should be asked for the best relaxation possible for higher reliability of SSEPs.