Seung-Dal Song

Analysis of somaclonal variation through tissue culture and chromosomal localization of rDNA sites by fluorescent in situ hybridization in wild Allium tuberosum and a regenerated variant

The effects of basal media and growth regulators on callus initiation and shoot regeneration have been investigated in wild Allium tuberosum (2n = 4x = 32). Callus initiation was greatest from flower bud explants cultured on MS medium supplemented with 2,4-D and BA at 1 mg l−1 each. Maximum number of shoots was obtained from callus grown on MS medium supplemented with NAA and BA at 0.2 and 2 mg l−1, respectively. The chromosome analysis of regenerants derived from callus revealed variation in ploidy, such as 2n = 28, 29, 30, 31, 33 as well as normal tetraploid. During the culture period for two generations, one aneuploid regenerant with 2n = 30 (named At30) showed better viability and growth than tetraploid plants and other aneuploid variants. In a karyotypic analysis of At30, the chromosomal positions of 5S and 18S-5.8S-26S rDNA were physically mapped by fluorescent in situ hybridization and compared to chromosomes of wild type A. tuberosum. Both wild type A. tuberosum and At30 exhibited two sets of 5S rDNA sites, one on the proximal position of the short arm of chromosome 3, and the other on the intercalary region on the long arm of chromosome 6. There was one 18S-5.8S-26S rDNA site in the secondary constriction including flanking short chromosomal segments of satellite and terminal regions on the short arm of chromosome 8 in wild type A. tuberosum. However, At30 showed only three labelled chromosome 8 indicating that this was one of the lost chromosomes of At30.

Karyotypes of three somaclonal variants and wild plants ofAllium tuberosum by bicolor FISH

Using the fluorescence in situ hybridization (FISH) technique, we conducted karyotype analyses to identify the lost chromosomes in three somaclonal variants obtained from tissue culture of wildAllium tuberosum (2n = 4X = 32). The three lost chromosomes of the At29 variant (2n = 29) were all chromosome 2, the two for At30 (2n = 30) were chromosomes 7 and 8, and At31 was missing chromosome 2. Chromosome compositions of these variants were confirmed as being fixed lines during two years of greenhouse cultivation. The bicolor FISH technique, involving both 5S and 18S–5.8S–26S ribosomal RNA genes as probes, was used to assign chromosomal locations and to confirm whether the lost chromosomes contained any rRNA markers. The 5S rRNA gene signals in all variants as well as the wild type were detected as two sets, one on the intercalary region of the short arm of chromosome 3, the other on the intercalary region of the long arm of chromosome 6. One 18S–5.8S–26S rRNA gene site on the secondary constriction included a flanking satellite and terminal region on the short arm of chromosome 8. Signals of the 18S–5.8S–26S rRNA gene in At30 showpd in only three chromosomes, indicating that one of the lost chromosomes was chromosome 8. Overall, three marker chromosomes were established by FISH, using rRNA multigene families.

Chromosome analysis by fluorescence in situ hybridization of callus-derived regenerants in Allium cyaneum R.

Abstract Investigations were performed to confirm the optimal in vitro culture condition for callus induction and plant regeneration, to observe if somoclonal variation occurs among regenerated plants at the ploidy level and to analyse the chromosomal location of 5S and 18S-26S rRNA gene families using fluorescence in situ hybridization in callus-derived plants of Allium cyaneum. High-est callus initiation was achieved with bulb explants cultured on MS medium supplemented with 2,4-D and BAP at 1 mg l–1 each. A total of 195 plants was obtained when using MS medium supplemented with 1 mg l–1 NAA and 5 mg l–1 BAP; about 92% were diploid having 2n=16; 8% showed a variation in ploidy level. Using digoxigenin-labelled 5S rRNA and biotin-labelled 18S-26S rRNA gene probes, we compared the fluorescence in situ hybridization patterns of autotetraploid plants with the A. cyaneum wild type. The 5S rRNA gene sites were detected on the interstitial region in the short arm of chromosome 4 and on the interstitial region in both arms of chromosome 7. The 18S-26S rRNA gene sites were detected on the terminal region of the short arm, including the satellite of chromosome 5, as well as on a part of chromosome B. The chromosomal location of both rRNA genes in regenerated autotetraploid plants corresponded to those of the wild species.

Effects of salinity on growth and patterns of ions and organic solutes in five sedges (Carex spp.) with different ecological demands

Summary The present study examines whether halophilous Carex distans , which is adapted to saline habitats, excludes salt ions under controlled conditions and whether the salt exclusion is also effective in non-halophilous Carex species from oligo- ( C. limosa, C. rostrata ), meso- ( c. pilosa ) and eutrophic ( c. acutiformis ) habitats. For C. limosa and C. rostrata , especially from oligotrophic sites, salt is never an ecological factor; therefore, this comparison is regarded rather as a heuristic model to characterize the solute pattern of genus Carex . The five species were grown in 2 different concentrations of Na-salt (control, 10mM and 40mM). Salt-tolerant C. distans exhibited no visible injury symptoms, but non-halophilous species showed reduced growth, especially at 40mM salt, and less NaCl excluding capacity. In conclusion, in moderate salinity (40 mM) the investigated Carex species showed considerable salt resistance associated with the ability to exclude Na + (esp. C. distans ) and to maintain high leaf K + levels. Particularly, proline, betaines and sugar alcohols, known to act as ‘compatible solutes’, were not synthesized as a response to salinity. Although nonhalophilous Carex species showed less salt exclusion capacity than C. distans, the investigated Carex species generally belong to the ‘monocot physiotype’, characterized by high K + contents, high exclusion capacity for soil ballast ions such as Na + , Ca 2+ and heavy metals and an effective overall regulation of ion absorption.

Influence of light regime on nitrate reductase activity and organic and inorganic solute composition of four sedges (carex spp.)

A survey was conducted on the inorganic and organic solute patterns of plants in connection with nitrate metabolism according to different light regimes (1.9, 16.0, 91.5 Wm‐2). Besides measuring in vivo NRA, we also quantitatively analyzed water‐soluble inorganic ions, organic acids, low molecular weight carbohydrates, amino acids and total N (% DW). Among 4 Carex species, C. pilosa is known as a shade‐adapted species and the others as half (C. gracilis) to full (C. rostrata & C. distans) light‐adapted specjes. Compared to species adapted to high light intensity, shade‐adapted C. pilosa showed reduced productivity under the highest light intensity. In general, nitrate and amino acid levels decreased at higher light intensity, while sugar and organic acid concentrations increased. In C. pilosa osmolality tended to rise with increasing light intensity, while in the other species it tended to fall. Under low light intensity, the drop in soluble carbohydrate contents is osmotically compensated for by an enhan...

Effects of Environmental Stresses on the Growth and Nitrogen Fixation of Melilotus suaveolens

The effects of environmental stresses on the growth and nitrogen fixation of Melilotus suaveolens, a biennial leguminous plant growing on the disturbed area in Korea, were examined in the field and growth chamber. The formation and activity of nitrogen fixing nodules are closely related with the nitrogen demand of host plant and the nitrogen content in the soil. Photosynthate provides carbon compounds to be used as energy sources for dinitrogen fixation. The major factors affecting seasonal variations of nitrogenase activity are temperature and photoperiod controlling photosynthesis.