• Journal of Korean Society of Forest Science
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• v.105 no.3
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• pp.309-314
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• 2016

A locally adapted plant population under harsh environmental changes might survive for a long generation through maintaining proper level of genetic diversity. When it happens losing the genetic diversity too much fast, the population could be declining and probably become extinct. An isolated small population of Populus davidiana was investigated to study out the genetic diversity and the fine-scale spatial genetic structure. The estimated number of adult trees in the population of Mt. Worak, South Korea, was 350 in the total area of $14,000m^2$. The number of adults in a study plot ($70m{\times}70m$) was 123. The average age was 16-year-old and a 32-year-old tree was the oldest. The distribution of individuals was slightly aggregated in the plot. Sixty-one among the 123 individuals were randomly sampled to estimate genetic variation using AFLP markers. One hundred fifty-one (77%) of total 196 amplicons were polymorphic from six AFLP primer combinations. The average number of loci per primer combination was 32.7 (S.D.=7.2). Expected heterozygosity ($H_e$) and Shannon's diversity index (S.I.) were 0.154 and 0.254, respectively. These values were extremely lower than those of other P. davidiana populations in South Korea. Genetic patchiness was showed within 21 meters by spatial autocorrelation analysis and the isolated small size of population might be mainly attributed to the formation of such small patch size.

• Animal cells and systems
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• v.5 no.4
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• pp.309-312
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• 2001

Allozyme studies have been widely used to estimate genetic variation and to describe genetic structure in natural populations. In many cases, the genetic diversity of recently established populations is generally lower than that of central populations. In addition, the genetic composition of an invasive species is influenced by its History of introduction as well as its ecological characters. Ageratina altissima (L.) R. King & H. Robinson (white snakeroot) is a perennial herb native to the eastern United States and Canada, and is currently receiving much attention for its rapid invasion of the Korean forests. Starch gel electrophoresis was used to assess the genetic variability at 11 putative loci in seven introduced populations of A. altissima in Seoul. Populations of A. altissima maintained lower levels of allozyme diversity (expected heterozygosity = 0.063) than those reported for other taxa with similar ecological traits. The degree of differentiation observed among A. altissima populations was considerably low. It is suggested that the populations were recently established from only a few founders via dispersal by human activities, resulting in the loss of genetic variation.

• Korean Journal of Plant Resources
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• v.32 no.3
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• pp.244-253
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• 2019

In crop breeding program, information about genetic dissimilarity on breeding resources is very important to corroborate genealogical relationships and to predict the most heterozygotic hybrid combinations and inbred breeding. This study aimed to evaluate the genetic variation in Kenyan sunflower breeding lines based on simple sequence repeat (SSR). A total of 83 alleles were detected at 32 SSR loci. The allele number per locus ranged from 2 to 7 with an average of 2.7 alleles per locus detected from the 24 sunflower accessions and the average value of polymorphic information contents (PIC) were 0.384. A cluster analysis based on the genetic similarity coefficients was conducted and the 24 sunflower breeding resources were classified into three groups. The principal coordinates (PCoA) revealed 34% and 13.38% respectively, and 47.38% of total variation. It was found that the genetic diversity within the Kenyan sunflower breeding resources was narrower than that in other sunflower germplasm resources, suggesting the importance and feasibility of introducing elite genotypes from different origins for selection of breeding lines with broader genetic base in Kenyan sunflower breeding program.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.54 no.4
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• pp.441-451
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• 2009

In this study, 29 simple sequence repeat (SSR) markers were used to analyze the genetic diversity and population structure of 125 rice accessions from 40 different origins in Africa, Asia, Europe, South America, and Oceania. A total of 333 alleles were detected, with an average of 11.5 per locus. The mean values of major allele frequency, expected heterozygosity, and polymorphism information content (PIC) for each SSR locus were 0.39, 0.73, and 0.70, respectively. The highest mean PIC was 0.71 for Asia, followed by 0.66 for Africa, 0.59 for South America, 0.53 for Europe, and 0.47 for Oceania. Model-based structure analysis revealed the presence of five subpopulations, which was basically consistent with clustering based on genetic distance. Some accessions were clearly assigned to a single population in which >70% of their inferred ancestry was derived from one of the model-based populations. In addition, 12 accessions (9.6%) were categorized as having admixed ancestry. The results could be used to understanding the genetic structure of rice cultivars from these regions and to support effective breeding programs to broaden the genetic basis of rice varieties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.1-11
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• 2008

Stiffness estimation of a shear building due to local damages is usually achieved though structural analysis based on the assumed material properties and idealized numerical modeling of structure. Conventional numerical modeling, however, frequently causes an inevitable error in the structural response and this makes it difficult to exactly predict the damage state in structure. To solve this problem, this paper introduces a damage detection technique for shear building using genetic algorithm. The introduced algorithm evaluates the damage in structure using a flexibility matrix since the flexibility matrix can exactly be obtained from the field test in spite of using a few lower dynamic modes of structure. The introduced algorithm is expected to be more effectively used in damage detection of structures rather than conventional method using the stiffness matrix. Moreover, even in cases when an accurate measurement of structural stiffness cannot be expected, the proposed technique makes it possible to estimate the absolute change in stiffness of the structure on the basis of genetic algorithm. The validity of the proposed technique is demonstrated though numerical analysis using OPENSEES.

• Journal of Navigation and Port Research
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• v.33 no.9
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• pp.635-644
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• 2009

The optimum design of power yacht belongs to the nonlinear constrained optimization problems. The determination of scantlings for the bow structure is a very important issue with in the whole structural design process. The derived design results are obtained by the use of real-coded micro-genetic algorithm including evaluation from Lloyd's Register small craft guideline, so that the nominal limiting stress requirement can be satisfied. In this study, the minimum volume design of bow structure on the power yacht was carried out based on the finite element analysis. The target model for optimum design and local structural analysis is the bow structure of a power yacht. The volume of bow structure and the main dimensions of structural members are chosen as an objective function and design variable, respectively. During optimization procedure, finite element analysis was performed to determine the constraint parameters at each iteration step of the optimization loop. optimization results were compared with a pre-existing design and it was possible to reduce approximately 19 percents of the total steel volume of bow structure from the previous design for the power yacht.

• Journal of Korean Society of Forest Science
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• v.102 no.1
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• pp.122-128
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• 2013

Genetic diversity and population genetic structure were estimated in nine natural populations of Exochorda serratifolia in South Korea using ISSR marker system. Average of polymorphic loci per primer was 5.8 (S.D.=2.32) and percentage of polymorphic loci per population was 78.7% with total 35 loci from 6 ISSR primers. In AMOVA, 27.8% of total genetic variation came from genetic difference among populations and 72.2% was resulted from difference among individual trees within populations. Genetic differentiations by Bayesian inference were 0.249 of ${\theta}^{11}$ and 0.227 of $G_{ST}$. Inbreeding coefficient for total populations was 0.412. There was significant correlation between genetic distance and geographic distance among populations. On the results of Bayesian cluster analysis, nine populations were assigned into three groups. The first group included 5 populations, and the second and the third had two populations per group, respectively. These three regions could explain 10.0% of total genetic variation from hierarchical AMOVA, and the levels of among-population and among-individual were explained 19.7% and 70.3%, respectively. The geographic distribution of populations following the three Bayesian clusters could be explained with mountain range as Baekdudaegan which is the main chain of mountains in Korea. The mountains as the physical barrier might hamper gene flow in the pearlbush. So when protected areas are designated for conservation of this species, we should consider those three regions into considerations and would better to choose at least one population per region.

• Journal of Korean Society of Forest Science
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• v.98 no.1
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• pp.1-7
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• 2009

We investigated the genetic variation and structure in Korean Arborvitae (Thuja koraiensis Nak.), by 29 examining I-SSR polymorphic loci in 84 individuals distributed among four natural populations in Korea. The level of population genetic diversity ($A_e$=1.44, P=72.42, $H_e$=0.258, S.I.=0.385) was similar to or slightly higher than that of plants with similar ecological traits and life history (Cupressaceae). Most genetic diversity was allocated among individuals within populations (${\Phi}_{ST}$=0.13). The UPGMA dendrogram based on genetic distance failed in showing decisive geographic relationship. The Mt. Bangtae population had the lowest level of genetic diversity and was the most distinctive from the other populations. Mt. Jang population which is possessed of the highest level of genetic variation and Mt. Bangtae population which is consisted of heterogeneous was considered to be a prime candidate for the conservation studies.

• Journal of Korean Society of Forest Science
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• v.103 no.1
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• pp.59-64
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• 2014

This study describes analysis of genetic diversity and spatial genetic structure of Korean poplar (Populus koreana Rehder) in Mt. Odae using I-SSR markers. P. koreana is a deciduous broad-leaved tree species that primarily grows in the alpine valleys of China, Russia and North Korea. In South Korea, P. koreana is found limitedly in Gangwon province. Especially, the population in Mt. Odae is located on the southern limit line, its importance is emphasized from the genetic resource conservation perspective. The Shannon's diversity (I=0.230) and the expected heterozygosity (He=0.151) were relatively low as compared with those of other plant species. Spatial autocorrelation analysis using Tanimoto's distance showed that the genetic patch was founded within 400 m. It is suggested that individual trees for ex situ conservation should be sampled with a minimum distance of 400 m between trees.

• The Plant Pathology Journal
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• v.33 no.3
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• pp.296-306
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• 2017

Sugarcane mosaic virus (SCMV) is one of the most damaging viruses infecting sugarcane, maize and some other graminaceous species around the world. To investigate the genetic diversity of SCMV in Iran, the coat protein (CP) gene sequences of 23 SCMV isolates from different hosts were determined. The nucleotide sequence identity among Iranian isolates was more than 96%. They shared nucleotide identities of 75.5-99.9% with those of other SCMV isolates available in GenBank, the highest with the Egyptian isolate EGY7-1 (97.5-99.9%). The results of phylogenetic analysis suggested five divergent evolutionary lineages that did not completely reflect the geographical origin or host plant of the isolates. Population genetic analysis revealed greater between-group than within-group evolutionary divergence values, further supporting the results of the phylogenetic analysis. Our results indicated that natural selection might have contributed to the evolution of isolates belonging to the five identified SCMV groups, with infrequent genetic exchanges occurring between them. Phylogenetic analyses and the estimation of genetic distance indicated that Iranian isolates have low genetic diversity. No recombination was found in the CP cistron of Iranian isolates and the CP gene was under negative selection. These findings provide a comprehensive analysis of the population structure and driving forces for the evolution of SCMV with implications for global exchange of sugarcane germplasm. Gene flow, selection and somehow homologous recombination were found to be the important evolutionary factors shaping the genetic structure of SCMV populations.