• Journal of Sericultural and Entomological Science
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• v.4
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• pp.51-55
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• 1965

The aim of this work was to investigate the rate of hybrid vigor among the $F_1$ hybrids. The results obtained are as follows; 1. The rate of hybrid vigor in outbreedings(E$\times$J, ＆ J$\times$C) was higher than that in inbreedings in all the metric characters, especially in moulting laval weight. 2. In outbreedings, the $F_1$ between Europe and Chinese strain showed considerably higher rate of hybrid vigor than that of Japanese and Chinese. 3. The hybrid vigor rate of moulting larvel weight gave rise to be significant differences among the strains due to the maternal effects from newly hatched larvae to pupae.

• Journal of Sericultural and Entomological Science
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• v.10
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• pp.67-72
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• 1969

In order to analyse the correlation between the parents and their hybrids in the silkworm, which were reared in spring, the author has surveyed the various quantitative characters which are significant in genetics, and the hybrid vigor rate. The duration of larvae life is shorter in F1 Value an in the mid parents value, cocoon size biffer, pupa rate, cocoon crop from ten thousand silkworms just molted in the fourth instar, total cocoon weight and cocoon layer weight increases in comparison with the mid parents value. Although cocoon layer ratio only shows increasing by 0.3％ or so, it is too little to admit the effect. F1 value is nearly equal to parent value and there is no correlation between F1 hybrids value and their mid parents value.

• Korean Journal of Medicinal Crop Science
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• v.14 no.2
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• pp.107-112
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• 2006

Two Atractylodes species, A. japonica Koidz. ex Kitam. (AJ) and A. macrocephala Koidz (AM) were used in this study. AJ population had higher amounts of Sesquiterpenoids and stronger tolerance to root rot but less vigor of root growth than AM population. Two populations (AJ and AM) were crossed to make interspecific hybrid population. A total of 98 lines propagated clonally were selected from a cross of AJ and AM, and evaluated for contents of sesquiterpenoids, atractylon (ATLN) and atractylenolide III (AT3) using high performance liquid chromatography (HPLC), and growth characters such as plant height, stem number and root weight. HPLC profiles of the hybrids were compared with those of parent plants, and it demonstrated the production of introgression hybrid by crossing between AJ and AM. Of 98 clonal lines,10 lines were selected by 10% level based on the growth vigor and tolerance to root rot, and AJM2102-51 line showed the heaviest root weight (117.1 g/plant) among them. A total of 98 hybrid lines contained on average $0.16\;{\pm}\;0.10\;mg/g$ of $AT3,\;2.00\;{\pm}\;1.37\;mg/g$ of ATLN, and $2.16\;{\pm}\;1.40\;mg/g$ of total sesquiterpenoids, showing high coefficients of variation (above 65%). Ten lines having high contents of sesquiterpenoids were selected, and AJM2101-15 had the highest amount (9.83 mg/g) of ATLN, and showed 40.8 g/plant of root weight similar to mean value (39.9 g/plant) of hybrid lines. The result showed that the introgression of both characters of vigorous growth from AM and high sesquiterpenoids content from AJ could be possible to make new hybrid lines by crossing between AJ and AM.

• Journal of the Korean Society of Tobacco Science
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• v.15 no.2
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• pp.123-129
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• 1993

Mesophyll protoplasts derived from young leaves of Nicotiana rustica and N. tabacum cv Burley 21 were fused with the aid of polyethylene glycol(PEG). Cytological examination of protoplasts after PEG treatment revealed 12.8 % heterokaryocytes. After 7 weeks culture, the hybrid calli showing greenish white with a compact appearance were selected in contrast to parental type calli tinged with white or green color. The somatic hybrid plants were verified by morphological, biochemical and cyclological analysis. A heterosis effect for plant vigor and height was observed but the shape of leaves and flower characteristics were intermediate between N. tabacum and N. rutstica. The isozyme banding patterns for peroxidase of somatic hybrid lines were compared with the parent species. A number of isozyme bands derived from both parental species were found in the hybrids. Somatic hybrid plants have been successfully backcrossed to the parental N. tabacum particularly with somatic hybrid plants as female parents. These hybrid plants yielded small seeds, only few which were germinable.

• Korean Journal of Plant Tissue Culture
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• v.24 no.4
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• pp.239-256
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• 1997

Plants belonging to the category of 2n apomixis or agamospermy form embryos and seeds without the processes of normal meiosis and syngamy. Seeds produced in this way have identical genotype of their maternal parent. Three different types of agamospermy are recognized: diplospory, apospory, and adventitious (adventive) embryony. $F_1$ hybrid cultivars cannot be used as seed sources in the next ($F_2$) generation because this generation would be extremely variable as a result of genetic segregation. Hybrid vigor is also reduced in the $F_2$ generation. Therefore, parental stocks for hybrid seed production need to be maintained and cross must be continuously repeated. Agamospermic 2n apomixis would make it possible to fix the genotype of a superior variety so that clonal seeds faithfully representing that genotype could be continuously and cheaply produced independent of pollination. That is, $F_1$ hybrid seeds could be produced for many generations without loss of vigor or genotype alteration. Production of apomictic $F_1$ hybrid seed would be simplified because line isolation would not be necessary to produce seed or to maintain parental lines, and the use of male-sterile lines could be avoided. Overall, apomixis would enable a significant reduction in hybrid seed production costs. Additionally, the production of clonal seed is not only important for seed propagated crops, but also for the propagation of heterozygous fruit trees and timbers. Clonal seed would help avoid costly and time-consuming vegetative propagating methods that are currently used to ensure the large-scale production of these plants. Apomixis is scattered throughout the plant kingdom, but few important agricultural crops possess this trait Therefore, most research to date has centered on introgressing the trait of apomixis into agricultural crops such as wheat, maize, and some forage grasses from wild distant relatives by traditional cross breeding. The classical breeding approach, however is slow and often impeded by many breeding barriers. These problems could be surmounted by taking mutagenesis or molecular approach. Arabidopsis thaliana is a tiny sexually reproducing plant and is convenient in constructing and screening in molecular researches. Male-sterile mutants of Arabidopsis are particularly suitable genetic background for mutagenesis and screening for apomictic mutants. Molecular approaches towards isolating the genes controlling the apomictic process are feasible. Direct isolation of genes conferring apomixis development would greatly facilitate the transfer of this trait to wide variety of crops. Such studies are now in progress.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.4
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• pp.391-395
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• 1999

Barnyardgrass had relatively higher growth vigor at the earlier growth stage than inbred rice did, showing the 2 fold higher $\alpha$-amylase activity during the periods of germination and large leaf area Expansion with high net photosynthetic rate at the earlier autotrophic stage, but it performed weak growth at the late growth stage. However, the hlybrid rice Shanyou 63 had significantly higher $\alpha$-amylase activity and net photosynthetic rate than that of barnyardgrass, exhibiting heterosis for two physiologica1 traits during the germination (6~12 days) and autotrophic phase, respectively. Accordingly, hybrid rice, Shanyou 63, exhibited heterotic effect at the early growing stage when were presented with barnyardgrass. Shanyou 63 exhibited stronger tillering ability, faster leaf area expansion and higher net photosynthetic rate than those of barnyardgrass.

• Journal of Sericultural and Entomological Science
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• v.1
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• pp.5-8
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• 1960

가잠에 있어 교잡제1대가 실용상 유리한것은 1841년 Robinert씨가 처음 실험한 보고가 있었고 일본에 있어서는 1906년 외출구태랑씨가 구주관후 귀국즉시 일대잡종이 경제상 유리한 점을 주장하면서 일방으로는 국립잠업시험장에서 우선 시험하여 장려해온 결과 1912 년경부터 점차보급되어 기후 1920년경에는 사견의 전부가 일대잡종으로 전환되었다. 1917년 일본잠업시험장 보고에 의하면(총괄적보고) 1. 일반으로 사육일수는 원종의 어느편보다 또는 기평균식보다 단축한다. (중략)

• Journal of The Korean Society of Grassland and Forage Science
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• v.14 no.4
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• pp.288-294
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• 1994

Seedling vigor of introgressive hybrids between birdsfoot refoil 'MO-20"(Lotus corniculatus) used as the maternal parent and tetraploid(2n=4x=24)accession PI302921 narrowleaf trefoil(Lotus corniculatus L.), and parents were compared in terms of dry matter accumulation , net photosynthetic rate, dark respiration rate, and growth analysis. The hybrids showed better seedling vigor than PI302921 as they had lower dark respiration rate and higher relative growth rate (RGR) than PI302921. Hybrids grew faster than MO-20, but there was not significant difference between them. Net photosynthesis per unit area increased during three weeks after emergence without difference among the entries, then decreased sharply with leaf age and shading marking much differences among entries Dark respiration rate was very high just after emergence, after which it decreased rapidly until it reached a stable level at 1 week through 3 weeks of age, and then dropped again. In general, dark respiration, photosynthesis, and seedling growth of the hybrid was similar to those if MO-20. Although there are some reports about interspecific hybrids of Lotus species, it still remains as a new area for genetic improvement of seedling vigor of L. corniculatus.atus.

• Korean Journal of Plant Resources
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• v.20 no.5
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• pp.442-445
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• 2007

Seedlings height of hybrids varied depending on mating combinations. Among the progenies from the mating combination, P. thunbergii(CN4)$\times$P. densiflora(KW29) showed the best plant growth. The mean height of this combination was 521 cm at the age of 8 years(yrs), which was 9% higher than rest of the crosses. Seedlings height of progenies using P. thunbergii(JN37) as mother tree showed 28%, 33%, and 29% higher than those of open-pollinated progenies of the mother tree at the ages of 4yrs, 6yrs, and 8yrs, respectively. On the other hand, using P. densiflora (KB5) as father tree showed 45%, 48%, and 32% higher than those of open-pollinated progenies of the father tree. This result may be caused by hybrid vigor.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.1
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• pp.103-114
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• 1994

Pearl millet is a $C_4$ plant and summer crop originated from west Africa, and the sixth most important cereal in the world and the most widely cultivated millet in the semi-arid tropics as a major staple food crop. Its grain of higher quality protein is used to make unleavened bread chapatis and prepared as gruel, dumplings, couscous and beer. It is also used as animal feed and forage in both temperate and tropical regions because it has a capability to grow well not only in the fertile soil, but also in the poor and dry soil. Most of the current breeding procedures used in pearl millet are aimed at maximum exploitation of hybrid vigor for both grain and forage yields in Korea. Pearl millet is ideally suited for exploitation of heterosis using cytoplasmic male sterile lines as seed parent, and fertile inbred lines and open-pollinated cultivars as pollen parent. Pearl millet hybrids developed in Korea produced 3 to 7 tons of grain and 100 to 150 tons of green fodder per hectare.