Background : Cylindrocarpon root rot, caused by Cylindrocarpon destructans and Fusarium solani, is a major disease which lead to replanting failure in ginseng garden. Chlamydospores of C. destructans, generated by poor environmental condition, can survived more than ten years in soil without host plant, ginseng. Density of soil pathogens gradually decreased as the progress of time since ginseng was harvested. Methods and Results : Soil chemical properties was analyzed from soil samples of 43 regions in farmer’s ginseng garden to study the variation of content and the correlation among inorganic contents. Soil samples of 24 regions was also analyzed to study correlation between progressed-year after ginseng harvest and soil chemical properties. Variation of soil chemical properties in descending order was Fe, Zn, P2O4, NO3, Mn. The content of Fe and Zn were great variation among inorganic chemicals of soil of farmer’s field. Electrical conductivity to induce physiological demage in excessive concentration showed highly significant positive correlation with the content of NO3 and K. As the progress of year after ginseng harvest, the content of organic matter and zinc was increased, while pH and Na were decreased in farmer’s field to cultivate ginseng. There were highly significant positive correlation between the progress of year after ginseng harvest and zinc content in farmer’s field to cultivate ginseng. Ratio of root rot of 2-year-old ginseng showed significant positive correlation with K content, and negative correlation in experimental field cultured by six rotation crops for one year. Conclusion : Root rot by soil pathogens was closely related with the content of potassium and zinc in soil chemical properties.

Background : Root diseases caused by Cylindrocarpon destructans and Fusarium solani decrease the yield and quality of ginseng. Cylindrocarpon root rot is a major disease caused by replanting failure in ginseng garden. Methods and Results : Solarization was done in the infested soil of the greenhouse for summer season (from July 24 to Autumn 31, 2014) after putting green manure (Sudan grass) and calcium cyanamide (CC) into the soil. Mycelium and conidia of C. destructans died at 4 0℃ after 15 hours, and 45℃ after 5 h, but it did not die at 35℃ after 15 h. Those of C. destructans died after keeping it for 2 hours daily at 40℃ for 9 days, and 45℃ for 8 days, but did not die at 38℃ for 9 days. Maximum soil temperature was 55.4℃ in 5 cm depth, 48.7℃ in 10 cm, 44.7℃ in 15 cm, 42.5℃ in 20 cm, and 31.9℃ in 30 cm by putting green manure into the soil and solarization. Reduction of sudan grass increased electrical conductivity (EC), organic matter, P2O5, K, and Mg, while decreased pH, NO3-N, and Na. Addition of calcium cyanamide and urea gave a negative effect on the growth of ginseng because EC and NO3-N were increased excessively than the optimal range. Solarization using green manure mixed with CC was the most effective in decreasing soil-borne pathogens of 2-year-old ginseng. But the root disease that occurred between single treatment of sudan grass and the treatment mixed with calcium cyanamide showed not a significant different. Addition of calcium cyanamide showed the decrease of root weight because leaves were dead early by a excessive increase of EC and NO3-N. Conclusion: Soil disinfection using green manure and solarization in greenhouse was effective in inhibiting root rot, however, it did not completely kill the soil-borne pathogens.

Ionizing radiation directly and indirectly affects gene expression within the plant genome. To access the physiological response of rice to different types of ionizing radiation, rice seeds were exposed to gamma-ray and ion beam radiation. Exposure to ionizing radiation dramatically decreased the shoot length compared with non-irradiated plants. Fluorescence-activated-cell-sorting (FACs) was used to measure DNA contents. There were significant correlations of dose-dependent between irradiated plant and non-irradiated plant. The radicals induced by the ionizing radiation in the plant could be observed by electron spin resonance (ESR). It was confirmed that the number of free radicals in cell was greatly increased all irradiated plants than non-irradiated plant. A significant positive correlation was shown between ionizing radiation dose and signal intensity. In order to determine the Genetic diversity, AFLP analysis was conducted with the irradiated plant and non-irradiated plant. Based on band patterns, the cluster analysis was conducted to evaluate the genetic variation by using the UPGMA (Unweighted Pair Grouping Method of Averages). Genetic diversity of irradiated plants by low dose ion beam was the closest non-irradiated plant and irradiated by high dose gamma-ray was the furthest from non-irradiated. We describe the detailed methods of ionizing irradiation and discuss its applications in genetic research as well as plant breeding.

xBrassicoraphanus, a new synthetic intergeneric hybrid between Brassica rapa L. ssp. pekinensis and Raphanus sativus L., also locally known as ‘Baemoochae’, is an interesting subject for studying polyploidy and genome plasticity in the family Brassicaceae, but very few genomic and cytogenetic information. Here, we analysed the chromosome complements and pairing of the most fertile lines, BB1 and BB5, using dual-color fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH) to check their chromosomal segregation stability. The somatic chromosome complement of B. rapa was confirmed to be 2n=20 (2.8~4.8μm), of R.sativus, 2n=18 (2.0~3.3μm), and of xBrassicoraphanus, 2n=38 (2.2~5.0μm). There were eight, eight, and seventeen metacentric pairs and two, one, and two submetacentric pairs in B. rapa, R. sativus, and xBrassicoraphanus, respectively. Additionally, three, two, and five pairs of 5S rDNA and five, three, and eight pairs of 45S rDNA were observed in B. rapa, R. sativus, and xBrassicoraphanus, respectively. This suggests that both B. rapa (AA) and R. sativus (RR) genomes, particularly the rDNA arrays, co-exist in xBrassicoraphanus (AARR) genome. In meiosis I, nineteen bivalents were most frequent, and GISH analysis showed ten bivalents from the A genome. This study would provide a useful information for further genomic study of xBrassicoraphanus and its improvement as a new promising breeding variety.

Compared to wide ranges of genetic variation of natural populations, very limited Miscanthus cultivar has been released. This study was the first report on the development of Miscanthus cultivar by means of radiation breeding. Seeds of M. sinensis were initially exposed to gamma rays of 250 Gy for 24 h, generated from a 60Co gamma-irradiator. The irradiated seeds were sown and then the highly tiller-producing mutants were selected for this study. Biomass-related parameters including tiller number, plant height, stem diameter, and leaf number were measured. Ploidy level and internal transcribed spacer (ITS) were investigated to characterize the mutants compared to wild type (WT) Miscanthus. Plant height and tiller number were negatively related, where multi-tillering mutants were relatively short after 4 month growth. However stem diameter and leaf number were greater in mutants. All the materials used in this study were diploid, implying that the mutants with greater tiller numbers and stem diameter were not likely related to polyploidization. Based on the sequence of ITS regions, the mutants demonstrated base changes from the gamma irradiation where G+C content (%) was decreased in the ITS1, but increased in ITS2 when compared to WT sequence. ITS2 region was more variable than in ITS1 in the mutants, which collectively allows identification of the mutants from WT. Those mutants having enhanced tillers and allelic variations might be used as breeding materials for enhanced biomass-producing Miscanthus cultivars.

Cytoplasmic male sterility (CMS) and fertility restoration have been utilized as valuable tools for F_1-hybrid seed production in many crops despite laborious breeding processes. Molecular markers for the selection of CMS-related genes help reduce the expenses and breeding times. A previously reported genomic region containing the Ppr-B gene, which is responsible for restoration of fertility and corresponds to the Rfo locus, was used to develop gene-based or so-called "functional" markers for allelic selection of the restorer-of-fertility gene (Rfo) in F_1-hybrid breeding of radish (Raphanus sativus L.) Polymorphic sequences among Rfo alleles of diverse breeding lines of radish were examined by sequencing the Ppr-B alleles. However, presence of Ppr-B homolog, designated as Ppr-D, interferes on specific PCR amplification of Ppr-B in certain breeding lines. The organization of Ppr-D, resolved by genome walking, revealed extended homology with Ppr-B even in the promoter region. Interestingly, PCR amplification of Ppr-D was repeatedly unsuccessful in certain breeding lines implying the lack of Ppr-D in these radishes. Ppr-B could only be successfully amplified for analysis through designing primers based on the sequences unique to Ppr-B that exclude interference from Ppr-D gene. Four variants of Rfo alleles were identified from 20 breeding lines. A combination of three molecular markers was developed in order to genotype the Rfo locus based on polymorphisms among four different variants. These markers will be useful in facilitating F_1-hybrid cultivar development in radish.