• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.4
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• pp.353-358
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• 1994

Grain yields of errect-leaved corn hybrids were reported to be increased as planting density(PD) increased compared to those of horizontal leaf type hybrids. This trial was conducted to investigate the difference between errect and horizontal-leaved hybrids in response to different PD. Grain yields of both type hybrids were decreased at the highest PD, however, that of horizontal-leaved hybrid, Ga209 ${\times}$ Ki14A, was decreased more than errect-leaved hybrids which indicated varietal difference in response to PD. Responses to PD for days to tasseling, plant height, ear height, and leaf angle were not significant, also, PD ${\times}$ hybrid interactions were not observed. Yield components were decreased as PD increased and there were no PD ${\times}$ hybrid interactions for these characters. Leaf angle was negatively correlated with grain yield and yield components except for kernel weight.

• Journal of Korean Society of Forest Science
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• v.89 no.1
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• pp.18-23
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• 2000

Leaves of various, 3 to 5-year-old Quercus hybrids were intermediate in size between their parental species. The petiole length was the smallest in the hybrids of Q. dentata ${\times}$ Q. crispula $F_1$ and was intermediate in the hybrids of Q. aliena ${\times}$ Q. serrata $F_1$ and Q. dentata ${\times}$ Q. aliena $F_1$ between their parents. The number of serration in hybrids was close to their mother tree's in most of crossing combinations. The serration depth and the ratio between longitudinal and transverse length of leaves were intermediate between the values of their parental species.

• International Journal of Industrial Entomology and Biomaterials
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• v.5 no.1
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• pp.59-65
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• 2002

Parthenogenetic development, hybrid vigour and cocoon shape variability were studied in bivoltine F1 hybrids of the silkworm, Bombyx mori L. Considerable breed differences were observed in parthenogenetic ability. Among the parental breeds, CSR18 exhibited maximum parthenogenetic development (79.65%) followed by CSR4 (67.90%). Among bivoltine F1 hybrids, CSR18 ${\times}$ CSR4 showed highest parthenogenetic development (73.32%) followed by CSR2 ${\times}$ CSR4 (55.43%). Study on hybrid vigour demonstrated that CSR18 ${\times}$ CSR19 expressed maximum significant hybrid vigour for all the seven economic characters over Mid Parent Value (MPV) followed by CSR2 ${\times}$ CSR4 and CSR18 ${\times}$ CSR4 exhibiting significant heterosis for six characters. Cocoon shape measurement study revealed that among ten bivoltine F1 hybrids, cocoons of three hybrids were found comparatively uniform. Importance of this study to know the level of paythenogenetic development, hybrid vigour and cocoon shape variability in different bivoltine F1 hybrids have been discussed.

• The Korean Journal of Zoology
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• v.13 no.4
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• pp.112-126
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• 1970

This paper deals with cytogenetical and cytochemical studies of the carp (Cyprinus carpio), the funa (Carassius carassius) and their hybrids. When kept under a confined condition, the carp and the funa mate andcan produce hybrids. Reciprocal crosses are also possible with similar results. The hybrids grow regularly with no observed abnormalities in the course of their development. They rank intermediate between the parent species in several characters. The hybrid males are completely sterile, while a hybrid female laid eggs in backcrossing. The spermatogenetic activity in hybrid testes is greatly disturbed. The chromosomes as observed in spermatogonial devision of hybrids are 100 in number, being the total sum of the haploid numbers of the parents, 50 for the carp and 50 for the funa. Meiosis in the hybrid testes is highly disturbed being arrested at early stages of the meiotic prophase. Most of the germ-cells undergo pycnotic degeneration during the period from late leptotene, and no spermatozoa are produced. In some hybrid specimens, the gonads show mosaic structures composed of testicular and ovarian elements, anevidence suggesting that sterility is associated with intersexuality caused by genetic unbalance between the parent species. The DNA amount in spermatogonial nuclei of thehybrids is approximately the same as that of liver nuclei, showing the 2n value. The DNA amount in the pachytene nuclei of the hybrids is less than the 4n value, while the parent species have the reduced amount of DNA in their pachytene nuclei. A consideration was made that the reduced amount of DNA in the hybrid cells may cause the disturbance of cellular activity leading to the subsequent degeneration of cells. Some aspects of enzymatic pattern in the carp, funa and their hybrids are. going on.

• Development and Reproduction
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• v.23 no.3
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• pp.239-253
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• 2019

We investigated the physiological responses of the river puffer, Takifugu obscurus, the tiger puffer, T. rubripes, a hybrids of the two (river puffer${\times}$tiger puffer) and a hybrid triploids to acute changes of salinity from 30 psu to 0 psu and from 0 psu to 30 psu. The blood and plasma factors of each species were elevated for 48, 72, or 96 hrs, and thereafter decreased due to hyper-osmoregulation and hypo-osmoregulation. In hyper-osmoregulation and hypo-osmoregulation, the cortisol concentration of river puffer, hybrids, hybrid triploids and tiger puffer increased for 12 or 48 hrs, and decreased thereafter. Chloride cells in the gill filaments of each species increased with increasing salinity, and melano-macrophages in the kidney tissue of each species increased with decreasing salinity. In conclusion, the hematological and stress responses of the hybrids were between those of the river puffer and tiger puffer, and the hematological responses of the hybrid triploids were higher than those of the other groups. The stress response of the hybrids was more sensitive than that of the hybrid triploids. In all groups, the histological responses of kidney in hyper-osmoregulation were more sensitive than those in hypo-osmoregulation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.1
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• pp.109-115
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• 2023

Interspecific hybridization is a beneficial strategy in aquaculture. In this study, diploid hybrids were produced through interspecies hybridization of flounder Platichthys bicoloratus ♀ × starry flounder P. stellatus ♂, which became commercial within a year. These hybrids exhibited an advantage in growth ability, with female hybrids growing twice as large as males at 11 months. Furthermore, hybrid flounders exhibited faster growth rates than starry flounders and reciprocal hybrids. The average growth rate of hybrids was 1.37 and 1.18 times greater than that of starry flounder and reciprocal hybrids at 5.5 months, respectively; Additionally, feed efficiency was 1.21 and 1.10 times higher than that of the experimental groups. The experiments were conducted at five temperatures to determine the optimal fry production method. Six weeks of culture resulted in a significant temperature effect, with maximum growth at 27℃. However, over 90% of the males occurred in the groups at temperatures above 24℃. Therefore, the optimum temperatures for survival, growth, condition factor and frequency of the best-sized fingerling at 13 weeks of age were estimated at 21℃. Thus, hybrid flounders are of great potential for use in the flounder aquaculture industry.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.5
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• pp.708-715
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• 2023

Hybridization is a major production method used to combine beneficial traits from two different species to obtain a potentially dominant trait. In China, Takifugu obscurus and T. rubripes were artificially crossed, and the resulting hybrids had an average body weight 38.06-8.93% higher than that of the parental species, which enabled the hybrids to be grown in freshwater. This study aimed to provide the basic data necessary for the classification of T. obscurus♀×T. rubripes♂ hybrids in terms of economic value and market potential. Morphological comparing the morphology of hybrids and parental species, we discovered that the hybrids had intermediate traits of the parental species. In morphometrics, the hybrid index (HI) value of head length against standard length was close to the trait of T. rubripes, and the HI values of preanal length and predorsal length were close to those of T. obscurus; however, the HI values of nasal length, snout length, length of anal fin, length of pectoral fin, caudal peduncle depth and caudal peduncle length were found to be unique characteristics of the hybrids. Regarding molecular analysis, a 99.8% nucleotide sequence similarity was found between the hybrid and T. obscurus.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.4
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• pp.476-482
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• 2013

The present study makes an investigation into expression of genes related to cardiac development in chicken, quail and chicken-quail hybrids during the early stage of embryogenesis. Real-time PCR was used to detect mRNA expressions of Nkx2-5, GATA4 and TBX5 in the heart of chicken, quail and chicken-quail hybrids embryos during the 3rd to 7th days of incubation. Results showed that NKX2-5 mRNA displayed a similar expression trend in chicken, quail and chicken-quail hybrids. The initial and highest expression of Nkx2-5 was focused on the 3rd day of incubation, then it declined till 5th day of incubation, thereafter, it fluctuated. Expression of Nkx2-5 gene in quail was significantly higher than in chicken and chicken-quail hybrids, and no significant difference was observed between the two latter species. GATA4 mRNA showed a similar expression trend between chicken and quail, which displayed a steady increase from 3rd to 6th d, then, the expression level decreased. However, GATA4 mRNA expression in chicken-quail hybrids was significantly higher than that in chicken and quail from 3rd to 5th d (p<0.01), but significantly lower than that in chicken and quail during the later stage of the experiment (p<0.05), due to the dramatic drop from 5th d onwards (p<0.01). TBX5 mRNA expression in chicken and quail showed the same trend as GATA4 expressed in the two species. Furthermore, TBX5 expression in chicken-quail hybrids was significantly higher than that in chicken and quail during the whole course of experiment, although relatively lower TBX5 expression was detected in the early stage. In conclusion, Nkx2-5, GATA4 and TBX5 genes showed dynamic changes during the process of cardiac development in chicken, quail and their hybrids embryos. In addition, the expression trend in chicken was similar to that in quail, and there was no significant difference for gene expression level, except NKX2-5. However, expression of these genes in chicken-quail hybrids was significantly different from their parents, the difference mechanism needs to be further explored.

• Journal of The Korean Society of Grassland and Forage Science
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• v.16 no.4
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• pp.327-337
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• 1996

A field experiment was conducted at SNU Experimental Livestock Farm, Suweon in 1995 to determine effect of planting date on forage performance of wm hybrids of four different maturity groups. A split-plot design replicated three times was used, with com hybrids representing four maturity groups (115, 118, 121 and 125 days) being the main plots and planting dates (3124, 415, 415, 425, 515 and 5/15) the sub-plots. 1. Days to emergence and percent emergence from the March 24 planting were, on the average, 36 days and 58%, respectively, but those from the April 5 to May 15 planting averaged 12 days and 92%, respectively. 2. Plant and ear heights increased gradually as the dates of planting were delayed except the May 15 planting, however, percent ear was decreased as the dates of planting were delayed. There was a trend for the mean lodging percentage of the hybrids to be higher as the planting date was delayed. 3. The 115-and 118-day mediumearly maturing hybrids harvested on August 18 produced silages with a dry matter content between 27 and 30% at all planting dates except the May 15 planting, while the 121-and 125-day medium-late maturing hybrids produced silages with a dry matter wntent less than 27% regardless of any planting dates. 4. There were no significant differences in mean dry matter yield among the hybrids, but significant mean TDN yield differences were found. The 115-, 118- and 125-day hybrids had significantly higher mean TDN yield than the 121-day hybrid. There were significant differences in mean dry matter and TDN yields among the planting dates. The mean dry matter and TDN yields from the April 5, 15 and 25 plantings were significantly higher than those of other plantings, however, there were no significant differences in mean TDN yield among the April 5, April 15 and April 25 plantings. No significant planting date $\times$ maturity interactions were found for both the dry matter and TDN yields. 5. Mean stover NDF and ADF contents of the 115- and 118day hybrids were higher than those of the 121- and 125-day hybrids, but the reverse was true for mean stover IVDMD and RFV. Mean stover NDF an ADF contents increased with earlier plantings, but mean stover IVDMD and RFV increased when planting was delayed. Results of this experiment indicate that for corn planting in central and northern areas of Korea, early to mid-April may be the right time with the 115-to 118-day maturity hybrids when silage making before August 20 is taken into consideration.

• Macromolecular Research
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• v.8 no.1
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• pp.44-52
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• 2000

Styrenic macromonomers with/without a silyloxy-functional group were synthesizedvia chain-end functionalization using 4-vinylbenzyl chloride as a terminating agent insec-butyllithium-initiated polymerization of styrene. The yields were 92 mol% for the silyloxy group and 88 mol% for the styrenic unit. Crystalline polystyrene-g-amorphous polystyrenes were synthesized by (η$^{5}$ -indenyl)-trichlorotitanium ((Ind)TiCl$_3$)-catalyzed copolymerizations of the macromonomers with styrene in the presence of methyl-aluminoxane (MAO) in toluene at 4$0^{\circ}C$. The macromonomer having $\alpha$, $\alpha$'-bis (4-[tert-butyldimethylsilyl-oxy]phenyl) group was also utilized for the preparation of a precursor of hydroxyl-functionalized syndio-tactic polystyrene. The obtained polymers were characterized by a combination of$^1$H, $^{13}$ C NMR spectroscopic, size exclusion chromatographic, and differential scanning calorimetric analysis. The (Ind)TiCl$_3$-catalyzed copolymerization of styrene with the macromonomer carrying the silyloxy functional group was found to be an efficient method to modify syndiotactic polystyrene without a great loss of physica] property by controlling the feud ratio of the macromonomer.