• Korean Journal of Plant Taxonomy
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• v.50 no.3
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• pp.361-367
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• 2020

We report meiotic chromosome numbers of three taxa in Carex sect. Mitratae in Korea: Carex breviculmis R. Br. (n = 32_II, 33_II, 34_II), C. polyschoena H. Lév. & Vaniot (n = 37_II, 38_II), and C. sabynensis Less. ex Kunth (n = 27_II). Section Mitratae is one of the most species-rich Asian groups in Carex, comprising approximately 45-80 taxa. Twenty-seven of these occur in Korea, and they are some of the most challenging taxa to identify due to their obscure and inconspicuous diagnostic characters. Including the counts reported here, half of the native Korean sect. Mitratae chromosome numbers have been documented. Their haploid chromosome numbers range from n = 10 to n = 40, and many exhibit variations in the numbers counted within a taxon. These variations, along with the overall significant variation in sect. Mitratae, suggest that dynamic chromosome activity may be related to the high species diversity of Carex.

• Current Research on Agriculture and Life Sciences
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• v.31 no.2
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• pp.75-82
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• 2013

Haploids are plants with a gametophytic number of chromosomes in their sporophytes. Androgenesis occurs from asymmetric division of pollen grains into generative cells and vegetative cells, followed by re-entry of the vegetative cell during S-phase, which causes microspores progress into G2/M transition in culture. One of the most interesting features of haploids is the possibility to produce doubled haploid (DH) individuals. Doubled haploidy is extremely useful to plant breeders because it enables shortened breeding periods and efficiency in selection of useful recessive agronomic traits. Doubled-haploid technology is not only applicable to breeding, but also to transformation programs of desired genes. In addition to practical breeding programs, DH lines provide useful materials of fundamental genetics including exploitation of QTLs and genes conferred with various agronomic traits by establishing DH populations. This paper provides historical overviews on androgenesis and describes several mechanisms associated with pollen embryogenesis, including mode of actions in pollen embryogenesis, mechanisms of chromosome doubling and factors affecting androgenesis. We also discuss recent progress in application of haploids to breeding, genes associated with in vitro response and drawbacks to anther culture for application of doubled haploids in crop breeding.

• Korean Journal of Plant Tissue Culture
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• v.28 no.4
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• pp.179-184
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• 2001

We evaluated a possibility of the use of chloroplast number per guard cell pairs as a measure for ploidy level in the different ploidy levels of tobacco plant (Nicotiana tabacum L. cv. BY-4) . The guard-cell chloroplast numbers of leaves of haploid plant were a half of wild-type plant. Furthermore, the number of chloroplast per guard cell pairs of the leaves of doubled-haploid plant increased in two times compared with that of haploid plant. In addition, the chloroplast number was not changed in the F$_1$ progenies. The change of the chloroplast number by leaf stage was not observed. The results indicate that there is a strong relationship between ploidy level (2x and 4x) and chloroplast number per guard cell pairs. This relationship was also, observed in both in vitro and pot cultured plants. It was determined that the measurement of chloroplast number in guard cells of leaf epidermis is simple to use and less labour intensive, and hence can be considered a practical alternative to the chromosome counting methods or flow cytometry in the tobacco plant.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.1
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• pp.74-78
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• 1991

This experiment was conducted to know the effects of mutagen treatments on callus induction, plant regeneration and their ploidy in the anther culture of wheat. The winter wheat cultivars, 'apos;and 'apos;Wonkwang'apos;, were treated at the mid or late-uninucreate stage under 4 different doses (100, 200, 500 and 1,000 rad.) of X-ray and 3 different levels(0.1, 0.2 and 0.3 mole) of Ethyl Methane Sulphonate. The anthers treated were set on the C$\_$17/medium for callus induction, and callus induced was transfered to 1/2 MS medium for plant regeneration. The mutagen treatments inhibited the callus induction but increased the plant regeneration in the callus which were induced from the anther set on the medium for the long time of 60 to 80 days. Also, the chromosome number to the regenerated plant varied largely by increasing of haploid plants(n=3x=21) and by occurring of aneuploidy having n=20 and n=22 of chromosome number.aried largely by increasing of haploid plants(n=3x=21) and by occurring of aneuploidy having n=20 and n=22 of chromosome number.

• Parasites, Hosts and Diseases
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• v.21 no.1
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• pp.118-124
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• 1983

The distribution, external morphology, radula, chromosome numbers of Planorbidae snails were studied. 1. The specimens were collected at four stations in Nonsangun, Kongjugun, and Daedukgun which are located around Geum river. Three genera and three species of Planorbidae, Hippeutis cantorir Segmentina hemisphaerula and Gyraulus cenvexiusculus, were collected. H. cantori was the most abundant species among the three species. G. convexiusculus was the least abundant one. 2. Each species could be identified on the basis of its external characteristic, since the periphery of each species has a peculiar shape. H. cantori was the largest one among the three species. 3. The radula formula of each species was very similar to other species. The size of radula was proportional to the size of shell. The radula formulae of H. cantori, S. hemisphaerula, and G. convexiusculus were 29 : 1 : 29, 23 : 1 : 23, and 16 : 1 : 16 respectively. The difference of radula formula could be found in the total numbers of laternal and marginal teeth. 4. The haploid chromosome number of H. cantori was eighteen (n=18), S. hemisphaerula and G. convesiusculus were assumed to be same in their chromosome numbers (n: 18).

• Journal of Plant Biotechnology
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• v.2 no.2
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• pp.109-113
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• 2000

Somatic hybrids were produced by electrofusion between embryogenic callus protoplasts of 'Syougun' mandarin and leaf protoplasts of grapefruit. Hybridity of the two plants was confirmed by leaf morphological characteristics and random amplified polymorphic DNA (RAPD) analysis. The cpDNA analysis using PCR-RFLP could not distinguish those of both parents. These plants showed normal growth and had chromosome number of 27. These unexpected triploid somatic hybrids might be derived from fused cells between diaploid protoplast of embryogenic calli and diploid protoplast of leaf, because polysomaty, a mixture of haploid cells and diploid cells was observed in the lactose medium-pretreated embryogenic calli of 'Syougun' by flow cytomehy analysis.

• The Korean Journal of Malacology
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• v.9 no.2
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• pp.30-43
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• 1993

The number of chronosomes and karyotypes in eight species of the family Bradybaenidae were analyzed by air-drying method using gonad. The mitotic haploid chromosome numbers of Acusta despecta sieboldiana were 29 and conisisted of 12 pairs metacentric, 17 pairs submetacentric chromosomes. The mitotic haploid chromosomes were 29 and 11 pairs metacentric and 17 pairs submetacentric and 1 pair telocentric chromosomes in Koreanohadra kurodana; 29 and 10 pairs metacentric chromosomes in K. koreana' 29 and 10 pairs metacentric and 18 pairs submetacentric, and 1 pair acrocentric chromosomes in Karaftohelix adamsi; 28and 10 pairs metacentric, and 18 pairs submetacintric chromosomes in Aegista chosenica; 28 and 14 pairs metacentric and 14 pairs submetacentric chromosomes in A.(Plectotropis) diversa; 28 and 15 pairs metacentric, 10 pairs submetacentric and 3 pairs acrocentric chromosomes in A. (p.)quelpartinsis; 29 and 12 pairs metacentric and 9 pairs submetacentric and 2 pairs telocentric chromosomes in Nesiohelix samarangae.

• Parasites, Hosts and Diseases
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• v.24 no.1
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• pp.42-48
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• 1986

As a series of systematic classification of paramphistomes, in the first step, paramphistomes in the lumen and reticulum were collected on 170 Korean catties (2∼3 years age, male) slaughtered at Jeonju abattoir from July, 1984 to September, 1985 and were classified by means of morphology of the worms. Afterwards, the karyotype of Paramphistomum explanatum (Creplin, 1849) which is the common in Korean cattle was detected by means of modified air-drying method from testis cells of the worm. The following is a brief summary of the leading facts gained through the experiment. 1. Most of the cattle slaughtered at the abattoir were infected with paramphistomes. The 5 species of the worms were detected on 170 Korean cattle and the worm burden per head was from 2 to 784(on the average 170) worms, 120(70.59%) heads out of them involving 2∼100 worms. In 28,900 individuals of paramphistomes obtained on 170 Korean cattle, appearance rates of various worms were as follows : 49.74% in P. explanatum, 48.08% in P. cervi, 0.98% in Orthocoelium orthocoelium, 0.89% in Fischoederius cobboldi and 0.14% in Cotylophoron cotylcphorum. 2. The chromosome number of 620 P. explanatum in the haploid and diploid cells was n=9 and 2n=18, and abundant cells in meiotic division were observed; 1,420 haploid and 38 diploid cells were reliable. Nine pairs of mitotic chromosomes were homologous and the chromosomes were composed of aye medium-sized metacentrics(m), subtelocentrics(st) or submetacentrics(sm) and four smallsized subtelocentrics(st) or submetacentrics(am), while meiotic metaphase chromosomes were composed of five medium and four small-sized. 3. The haploid of the testis cells showed C-band in the centromeric region from 8 of them, whereas the remaining chromosome No. 5 included heterochromatin on the tip region, and chromosomes No. 3 and No. 7 showed a remarkable C-band distinguished from other chromosomes.

• Korean Journal of Environmental Biology
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• v.20 no.1
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• pp.35-39
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• 2002

The significance of cell ploidy and repair ability for the radioprotective efficiency of cysteamine was studied in DNA repair - proficient and repair - deficient yeast cells irradiated $^{60}C0\;\gamma-rays.$ Results have been obtained for the cell survival of two groups of yeasts-diplont and haplont cells, both in haploid and diploid states. For diploid Saccharomyces cerevisiae yeast cells, the correlation between the radio-protective action of cysteamine and the cell repair capacity was demonstrated. Such a correlation was not clearly expressed for haploid yeast cells. In addition, evidence was obtained indicating that the degree of the radioprotective action was independent of the number of chromosome sets in haplont yeast Pichia guilliermondii cells and in some radiosensitive mutants defective in the diploid-specific recovery. It is concluded on this basis that the radioprotective action may involve the cellular recovery process, which may be mediated by a recombination-like mechanism, for which the diploid state is required. The results obtained clearly show that the radioprotective effect was dependent on DNA repair status and indicate that the mechanism of the radioprotective action may be realized on the level of primary radiation damage production as well as on the level of postradiation recovery from potentially lethal radiation damage.

• The Korean Journal of Zoology
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• v.13 no.2
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• pp.35-43
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• 1970

사람은 물론 모든 생물의 體細胞는 여러 타입의 染色體를 이중으로 지니고 있어서 倍數(diploid number)라하고 生殖細胞는 그의 한쪽만을 갖어서 半數(haploid number)라 한다. 1956년에 이르기까지도 사람의 染色體의 倍數는 48로 알려지고 性染色體 구성은 확실하지 못한 상태에 있었다. 1956년 이래 體細胞 染色體 硏究에 관한 기술 방법의 비약적인 발전으로 인하여 사람의 정상인 核型은 물론 異常形質을 나타내는 個體의 染色體에 관해서도 정확한 데타를 얻을 수 있게 되었다. 染色體硏究에 있어 개선된 기술방벙의 가장 큰 것은 組織培養의 도입이다. 종래의 切片作成法(section method)을 지양하고, 사람 몸에서 지극히 적은 분량의 組織을 얻어가지고 生體에서와 거의 비슷한 환경을 주어 인공적으로 단층의 細胞를 이루어 증식시키는 방법이다. 1956년 사람의 染色體를 정확히 파악하여 倍數로 46개이며, 남자는 XY, 여자는 XX 의 性染色體를 지닌다는 점을 밝힌 Tjio 및 Levan도 사람의 胎兒의 肺組織을 培養한 것을 재료로 삼았던 것이다.