• Korean journal of applied entomology
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• v.28 no.4
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• pp.237-243
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• 1989

These studies were conducted to investigate the development of chemical resistance in two-spotted spider mite (Tetranychus urticae Koch) through alternate selection for a given period of time with four acaricides including ethion of organophophours compound, dicofol of organo-chlorine compound, cyhexatin of organo-tin compound, and biphenthrin of synthetic pyrethroid compound; and to examine multiple-resistance among the acaricides to the selected populations. The development levels of chemical resistance in the two-spotted spider mite were greatly varied under alternate selection with the different chemical-group combination of four acaricides. Resistant levels of the ethion/dicofol-selected population at 13th-13th generation showed 49.4-fold resistance to ethion and 18.1-fold to dicofol; the ethion/cyhexatin-selected population at 9th-9th generation exhibited 28.1-fold to ethion and 5-fold to cyhexatin; the ethion/biphenthrin-selectd population at 10th-10th generation revealed 39.8-fold to ethion and 19.2-fold to biphenthrin. However, the dicofol/cyhexatin-selected population at 9th-9th generation showed 11.3-fold to dicofol and 4.9-fold to cyhexatin, and the dicofol/biphenthrin-selected population at 12th-12th generation exhibited 11.2-fold to dicofol and 9.4- fold to biphenthrin, while the cyhexatin/biphenthrin-selected population at 9th-9th generation revealed 3.7-fold to cyhexatin and 7.7-fold to biphenthrin. In case of alternate selection, the ehtion/dicofol-selected population revealed moderate multiple-resistance level to biphenthrin. The ethion/cyhexatin-selected and the ethion/biphenthrin-selected populations showed low mutiple-resistance level to biphenthrin and dicofol, respectively. However, the dicofol/cyhexatin-selected, the dicofol/biphenthrin-selected and the cyhexatin/biphenthrin-selected populations exhibited high multiple-resistance level to ethion.

• Korean journal of applied entomology
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• v.43 no.1
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• pp.43-48
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• 2004

Development of 3,700 folds resistance to etoxazole was found in the population of twospotted spider mite, Tetranychus urticae, collected from rose greenhouses in Buyo, Chungnam Provience in August 2000. This population was selected for 3yr with etoxazole to get 5,000,000 folds increase in resistance as compared to susceptible (S) strain. The etoxazole resistance was stablized for 16 months under the condition of no acaricide application. Inheritance and cross resistance in etoxazole to some acaricides of the etoxazole resistance strain (R) were investigated. There were differences of susceptibility in the etoxazole concentration-mortality relationships between $F_1$, $F_2$ progenies obtained from reciprocal cross with the S and R strains (R$_{♂}$${\times}$S$_{♂}$${\times}$R$_{♂}$). Degrees of dominance were 0.98 and 0.98 in $F_1$ and $F_2$ progenies of R$_{♂}$${\times}$S$_{♂}$, and -0.97 and -0.68 in $F_1$ and $F_2$ progenies of S$_{♀}$${\times}$R$_{♂}$ respectively. Inheritance in $F_1$ and $F_2$ progenies of R$_{♀}$${\times}$S$_{♂}$ were complete dominant. However $F_1$ and $F_2$ progenies of S$_{♀}$${\times}$R$_{♂}$ were incomplete recessive. These results suggest that inheritance of etoxazole resistance is controlled by a complete dominance. The R strain exhibited cross resistance to acequinocyl and emamectin benzoates in adult females, and milbemectin, amitraz and pyridaben in eggs. However they showed negatively correlated cross-resistance to bifenazate, a carbazate acaricide. These results may indicate bifenazate could be useful for the control of etoxazole resistant T. urticae population.

• Journal of Korean Society of Forest Science
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• v.14 no.1
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• pp.1-20
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• 1972

The trend and achievements of forest genetics research in abroad were investigated through observation tours and reference work and following facts were found to be important aspects which should be adopted in the forest genetics research program in Korea. Because of world wide recognization on the urgency of taking a measure to reserve some areas of the representative forest type on the globe before the extingtion of such forest type as the results of continuous exploitations of the natural forests to meet the timber demand all over the world, it is urgently needed to take a measure to reserve certain areas of natural stand of Pinus koraiensis, Pinus parviflora, Pinus densiflora f. erectra, Abies koreana, Quercus sp., Populus sp., etc. as gene pool to be used for the future program of forest tree improvement. And the genetic studies of those natural forest of economic tree species are also to be performed. 1. Increase of the number of selected tree for breeding purpose. Because of the fact that the number of plus tree at present is too small to carry out selection program for tree improvement, particularly for the formation of source population for recurrent selection of parent trees of the 2nd generation seed orchard it is to be strongly emphasized to increase the number of plus tree by alleviating selection criteria in order to enlarge the population size of plus trees to make the selection program more efficient. 2. Progeny testing More stress should be placed on carrying out progeny testing of selected trees with open pollinated seeds. And particular efforts are to be made for conducting studies on adult/juvenile correlation of important traits with a view to enable to predict adult performances with some traits revealed in juvenile age thus to save time for progeny testing. 3. Genotype-environment interaction Studies on genotype and environment interaction should be conducted in order to elucidate whether the plus trees selected on the good site express their superiority on the poor site or not and how the environment affect the genotype. And the justification of present classification of seed distribution area should be examined. 4. Seed orchard of broad leaf tree species. Due to the difficulty of accurate comparison of growth rate of neighbouring trees of broad leaf tree species in natural stand, it is recommended that for the improvement of broad leaf trees a seedling seed orchard is to be made by roguing the progeny test plantation planted densely with control pollinated seedlings of selected trees. 5. Breeding for insect resistant varieties. In the light of the fact that the resistant characteristics against insect such as pine gall midge (Thiecodiplosis japonensis U. et I.) and pine bark beetle (Myelophilus pinipera L.) are highly correlated with the amount and quality of resin which are known as gene controlled characteristics, breeding for insect resistance should be carried out. 6. Breeding for timber properties. With the tree species for pulp wood in particular, emphasis should be placed upon breeding for high specific gravity of timber. 7. Introduction of Cryptomeria and Japanese Cypress In the light of the fact that the major clones of Cryptomeria are originated from Yoshino source and are being planted up to considerably north and high elevation in Japan, those species should be examined on their cold resistance in Korea by planting them in further northern part of the country.