• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.2
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• pp.136-151
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• 1984

The purpose of this study is to find out the linkage relationship of the resistance genes Wbph1 and Wbph2 which are known to be present in the rice cultivar N22 and ARC 10239 respectively, with the genetic markers which are identified as the specific linkage tester. Crosses were made between the resistant parents and the genetic marker stocks and their F$_2$ populations were grown out in the field. The genetic segregations of the marker character were studied and the seeds were harvested individual plant base. These F$_3$ seeds were grown into plant-line base in the greenhouse and their responses to the whitebacked planthopper were tested. Then the linkage relationship between the F$_2$ plant marker character and the F$_3$ resistance responses to the whitebacked planthopper were examined. In the F$_2$ generation of the crosses between the resistant parent N22 and the genetic marker stocks, the genetic markers, such as lg, d-t, g, la, bl and gl, showed the segregation of 3 dominance to 1 recessiveness, and the Bh marker segregated into 9:7 ratio. Another 4 marker genes, such as Cl, gh, Lh and bc, did not show the good fittness to the expected value. In the F$_2$ generation of the crosses between the resistant parent ARC 10239 and the genetic marker stocks, the genetic markers, such as Cl, lg, Pn, g, la, bl and gl, showed the segregation of 3 dominance to 1 recessiveness, and the Bh gene segregation fitted well to the 9:7. The rest 4 genetic markers, such as gh, Lh, nl and be, did not show the good fitness to the expected ratio. The resistance genes Wbphl of N22 and the Wbph2 of ARC 10239 appeared to be single dominant gene each. The Wbphl gene was linked with the marker gene, liguleless (lg) of linkage group II with the recombination value of 36.8%, and with the black hull (Bh) with the value of 35.9%. The Wbph2 gene appeared to be independent of all the markers tested here, such as Cl, lg, Pn, g, Lh, la, nl, bl, bc, gl, Bh, of linkage gtoup I, II, III, IV, VI, VII, VIII, IX, X, XI, and XII respectively. That the Wbph2 linkage relations were not investigated was regarded as the causes that the tested marker genes on the chromosome were located with the resistance gene at the distant loci, and of the phenctypic properties of the marker characters. The Wbph2 linkage relations should be reexamined in the cross combinations of linkage group Ⅶ, Ⅷ, Ⅹ and XII including linkage group V which was not tested in this experiment.

• Journal of the Economic Geographical Society of Korea
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• v.25 no.1
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• pp.109-130
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• 2022

The Vietnamese government has proposed contract farming through a new type of cooperative as an institutional innovation which aims to restructure the agricultural sector. However, policy changes often impact farmers, who bear the primary effects of the transition process. Understanding households' strategies for land use and livelihood is crucial for policymaking in the agricultural development field. This study was conducted in the rural Binh Dao commune in Central Vietnam. We analyzed household members' labor force changes and their livelihood behaviors after their participation in a contract farming scheme using qualitative analysis methods combined with geographic information system (GIS) support, based on secondary data and in-depth interviews of 190 farmers. Simultaneously, we created a digital map of the cooperative's production area to investigate changes in land use and production activities. The findings show that contract farming shaped the vertical coordination of the value chain from the farmers to the cooperative and agricultural product trading companies. Subsequently, it encouraged land use and labor efficiency due to mechanical support. In addition, it also increased productivity and protected farmers from market risks. However, despite its positive effects on agricultural productivity in this case, the contract farming scheme could not achieve the restructuring of the rural labor force toward non-agricultural sectors. Ironically, farmers in the Binh Dao commune tended to increase cultivable land during the agricultural restructuring program, rather than switching their labor forces to non-agricultural sectors. The lack of stable non-farming job opportunities in rural Vietnam results in challenges to the efficiency of agricultural restructuring programs. Consequently, farmers in the Binh Dao commune are still smallholder farmers, depending on the family labor force.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.3
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• pp.264-274
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• 1993

This study was carried out to assess the agronomic characters and physicochemical properties of floury and chalky-endosperm mutant lines induced by chemical mutagen treatment to rice varieties, Hwacheongbyeo and IR24. Linkage analysis of a floury-endosperm gene was carried out using linkage testers. The grain size of brown rice of the mutants was smaller than that of the original varieties. The l, 000-grain and 1$\ell$ weight were lighter in the mutants compared with those in the original varieties. The compound starch granules in the endosperm cell of the mutants showed a loosely-packed crystalline structure. Amylose contents in mutants ranged from 16.9 to 28.5%. Crude protein contents of the mutants were not significantly different from the original rice variety, Hwacheongbyeo, but white core mutant(line 47106) derived from IR24 showed higher protein(l1.32%) compared with IR24(8.30%). The mutants showed slightly harder gel characteristics, and much lower viscosity in Amylograph than original varieties. Steamed rice-cakes from mutant lines showed greater volume than those from original varieties. During the process of alcohol fermentation, Brix in the mutants(especially floury mutants) decreased faster and the alcohol production after 10-day fermentation was much greater in the mutants than in the original varieties. Three different gene loci for floury endosperm characteristics were identified from the allelism test among mutant lines, and the genes were tentatively symbolized as flo-a, flo-b and flo-c, respectively. A floury gene, flo-a, was linked with lg(liguleless) gene in the linkage group N, with R.V. 5.76$\pm$1.72%.