• Journal of Life Science
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• v.7 no.4
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• pp.347-354
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• 1997

Some attempts were made to investigate the gentic characteristics of the brown planthopper(BPH), Nilaparvata lugens Sta${\aa}$l, biotypes. In terms of egg and nymphal periods, egg hatcgability, emergence ratio, and population change of BPH and plant damage of rice cultivars by the infestation of BPH biotypes and their hybrid progenies in field conditions. The egg and nymphal periods of the three of BPH biotypes and their hybrid progenies on Dongjinbyeo with no resistance gene were shorter than on rice cultivars with resistance gene. But the periods of biotype-2(♀) X 2(♂) (E) on Samgangbyeo with Bph-1 gene and biotype-3(♀) X 3(♂)(I) on Mirying 63 with bph-2 gene were as short as on Dongjinbyeo. The egg hatchability and emergence ratio of the three Bph biotypes and their hybrid progenies on Dongjinbyeo were higher than on the other rice cultivars, and those of E on Samgangbyeo and I on Miryang 63 were as high as on Dongjinbyeo. In rice paddy field, biotype-1(♀) X 1(♂)(A)$\sim$I infested on Dongjinbyeo, E onSamgangbyeo, and I on Miryang 63 were increased their population densities remarkably in next generation. Dongjinbyeo infested by A$\sim$I, and Myryang 63 infested by I were hopperburned at 60 days after infestation and had a damage rating of 0.9. But Samgangbyeo infested by E was no hopperburn(damage rating: 7.3) though it showed high BPH population at 60 days after infestation.

• Korean journal of applied entomology
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• v.22 no.2 s.55
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• pp.52-66
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• 1983

The brown planthopper, N. lugens (Stal), has become a serious pest of rice in tropical Asia during the last decade. At high pest density, its feeding damage causes 'hopperburn' or complete wilting and drying of the rice plant. It also transmits grassy and ragged stunt virus diseases. The estimated losses caused by the pest in tropical Asia exceed $US\$300$ millions. While cultivation of resistant rice varieties has proved to be highly effective against the pest, their long-term stability is threatened because of the evolution of prolific biotypes which can destroy these varieties. At present, identification of biotypes is based principally on the differential reactions of host rice varieties to the pest and on host-mediated behavioral and physiological responses of the pest. Recent findings of morphological differences in adult rostrum, legs, and antennae, body parts that possess receptors for host plant location and discrimination, and cytological differences in N. lugens populations maintained as stock cultures strongly complement other biotype studies. So far, three N. lugens biotypes have been identified in the Philippines. Biotype I can survive on and damage varieties that do not carry and genes for resistance, while Biotype 2 survives on resistant varieties carrying Bph 1 gene and Biotype 3 on varieties carrying gene bph 2. However, none of these biotypes can survive on varieties with genes Bph 3 or bph 4. Several varieties which are resistant in the Philippines are susceptible in India and Sri Lanka as the South Asian biotypes of N. lugens are more virulent than Southeast Asian biotypes. To monitor the pest biotypes in different geographical regions and to identify new sources of resistance, an International Brown Planthopper Nursery has been established in many cooperating countries. The evolution of biotypes is an exceedingly complex process which is governed by the interactions of genetic and biological factors of the pest populations and the genetic makeup of the cultivated varieties. While the strategy for sequential release of varieties with major resistance genes has been fairly successful so far, the monegenic resistance of these varieties makes them vulnerable to the development of the pest biotypes. Therefore, present breeding endeavors envisage utilizing both major and minor resistance genes for effective control of the pest.

• Weed & Turfgrass Science
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• v.6 no.4
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• pp.350-354
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• 2017

Conyza canadensis is the weed species which most frequently develops resistance to glyphosate in many agricultural crop fields. The continuous use of glyphosate has resulted in the spontaneous occurrences of resistant biotypes. This research was conducted to investigate the response of suspected C. canadensis biotypes to glyphosate. Seeds of C. canadensis were collected from 18 sites in tangerine orchards in Jeju province of Korea. In the preliminary screening, 6 resistant and 12 susceptible biotypes were found at the recommended glyphosate rate ($3.28kga.i.ha^{-1}$). The susceptible biotypes were completely killed at the field application rate whereas the resistant biotypes were initially injured but recovered 14 days after glyphosate application. This is the first case of glyphosate resistance found in Korea despite the national ban on genetically modified glyphosate tolerant crops cultivation. Extended monitoring should be conducted to understand how widely spread the glyphosate resistant C. canadensis is and to estimate the severity of this weed problem in the tangerine orchards of Korea.

• The Korean Journal of Ecology
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• v.26 no.2
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• pp.82-86
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• 2003

We investigated the variation in adaptation to growth for four ecotypically-differentiated population of Taraxacum officinale found naturally in temporal environmental heterogeneity. Seeds collected from the four seasons were germinated in incubators and were grown for four months in greenhouse to test genetic variation among biotypes. Biotypes, segregated by seeds collected seasonally, were the part of natural population in Mokpo, South Korea. Each biotype was different in total dry weight of seeds, biomass, and leaf area, confirming previous finding. Differences between biotypes grown under a common environment indicated a genetic basis to their distinct demographic rates. Therefore, biotypes with similar annual rates of growth and contrasting seasonal rates should persist in the population. This differential response suggests that temporal variation in environment may be responsible, in part, for the maintenance of genetic variation within populations.

• Korean journal of applied entomology
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• v.26 no.2 s.71
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• pp.63-69
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• 1987

This study was performed to evaluate the resistance of three different rice cultivars to the BPH biotypes 1, 2, 3 and their hybrid progenies, Nilaparvata lugens STAL. The rice cultivars tested were Chucheongbyeo, Cheongcheongbyeo and Milyang 63. The following characteristics of hybrid progenies were compared with these of their parents: Seedling response, Host preference, feeding amount, Esterase polymorphism of the brown rice. According to the responses of rice seedlings to the three BPH biotypes and their crosses progenies nymph, Chucheongbyeo was shown highly susceptible to their nymphs. The Cheongcheongbyeo was susceptible to the biotypes 2 and the Milyang 63 was susceptible to the biotype 3. The Cheongchengbyeo and the Milyang 63 were moderate to the biotypes 2(female)${\times}$3(male) and 3(female)${\times}$2(male). The preference in feeding and oviposition of three BPH biotypes and their hybrid progenies to Chucheongbyeo were shown higher than to another cultivars. The two preference were not only shown highly in Cheongcheongbyeo by the biotypes 2,2(female)${\times}$3(male) and 3(female)${\times}$2(male) but also in Milyang 63 by the biotypes 3,2(female)${\times}$3(male) and 3(femlae)${\times}$2(male). The feeding amount of female adult was much on three BPH biotypes and their hybrid progenies in Chucheongbyeo and on the biotypes 2 and 3(female)${\times}$2(male) in Cheongcheongbyeo, On the biotypes 3 and 3(female)${\times}$2(male) in Milyang 63 were as same as the above. The esterase bands of Est ${\alpha}-1,\;{\beta}-4,\;{\beta}-5\;and\;{\beta}-I$ were detected on brown rice of all the tested cultivars. The bands of Est ${\beta}-2\;and\;{\alpha}-I$ were detected on Cheongcheongbyeo (Bph 1 gene for resistance) and Milyang 63 (bph 2 gene for resistance). The Est ${\beta}-3\;and\;{\beta}-1$ of esterase bands were detected on Chucheongbyeo.

• Korean journal of applied entomology
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• v.32 no.1
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• pp.68-75
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• 1993

Morphometric investigations of the leg characters of both sexes of brachypterous Korean N. lugens biotypes were made. Simple and multivariate statistical analyses revealed that the three N. lugens biotypes differed from one another. The amount of variation and segregation between and among the three biotype populations were approximated by the scatter plot diagrams based on the computed discriminant scores. The variables of leg characters provided the most significant segregations of three biotype populations, thus, categorizing the three biotypes as distinct intraspecific populations of N. lugens.

• Korean journal of applied entomology
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• v.53 no.4
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• pp.465-472
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• 2014

The tobacco whitefly, Bemisia tabaci, infest the Oriental melon and give significant economic damage along with its virus-vectoring activity. Various biotypes of B. tabaci have been well known and are classified depending on the severity of crop damage and insecticide susceptibility. In this study, B. tabaci adults were collected in the melon fields located in Poongchun-myeon, Andong, Korea and diagnosed on their biotypes using PCR molecular markers. From the all the 11 greenhouses, B. tabaci biotype Q was identified. In addition, biotype B adults were also found from the 4 greenhouses. These results report the first occurrence of B. tabaci at the Oriental melon farms in Gyeongbuk province with mixed infection by the two biotypes in the area.

• Korean Journal of Veterinary Research
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• v.30 no.2
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• pp.193-201
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• 1990

An attempt was made to isolate Salmonella(S) organisms from a total of 4,587 fecal samples of birds during the period from May 1987 to March 1988, and serotype and biotypes of the isolates were also investigated. One hundred and sixty-six Salmonella strains were isolated from 151(3.3%) of 4,587 fecal samples of birds, and their serotype was all identified as S typhimurium var copenhagen. The positive samples of S typhimurium var copenhagen were 149 samples(5.1%) in pigeons and 2 samples (0.8%) in aquatic birds. No Salmonella was obtained from ducks, pheasant, and other birds. The isolation frequencies of S typhimurium var copenhagen from pigeons varied from 1.1 to 12.8% at 5 parks, it was higher in September and November. Biotypes of 166 S typhimurium var copenhagen strains isolated from pigeons and aquatic birds were all biotype 10 according to Brandis' method, and were biotype 25hi (78.3%), 27 hi (14.5%), 25 fhi (3.6%), 25 bhi (1.8%), 27 bhi (0.6%), 27 hiz (0.6%), and 9 hi (0.6%) according to Duguid's scheme. Appearance of different biotypes indicated the occurrence of exotic infection sources on the parks.

• Korean journal of applied entomology
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• v.31 no.4
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• pp.366-370
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• 1992

Salient chromosomal variations during the first meiotic division in primary spermatocyLes of the three brown planthopper, Nilaparvata lugens (Stal) , biotypes were observed. The meiotic index was highest in biotype 3 (58.6), followed by biotype 1 (39.4) and biotype 2 (23.6). Total chromosomal aberration including agmatoploidy, aneuploidy, loose pairings of sex chromosomes, and cytoplasmic shrinkage was found high in the order of biotype 1 (60.6%),2 (47.9 %), and 3 (38.1 %). However, percent agmatoploidy was highest in biotype 2 (19.6%) whereas in biotypes 3 and 1, it was 9.5% and 2.5%, respectively. The number of cells with isolated sex chrosomomes was observed highest in biotype 2.

• Korean journal of applied entomology
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• v.32 no.3
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• pp.317-322
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• 1993

Morphological investigations of the abdominal lateral lobes in females and the unguitractor p plates in the tarsi of legs in male and female N. lugens among the three Korean N. lugeηs bio-types revealed that the three biotypes varied from one another. The presence of a distinct ‘cut’ on the lateral lobes in brachypterous females distinguished Biotype 2 from Biotypes 1 and 3. The highest frequency of inserted unguitractor plates in fore-and mid-tarsal segments was exhibited by Biotype 2 in both sexes of each morphs.