• Horticultural Science & Technology
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• v.30 no.6
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• pp.757-763
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• 2012

To acquaint correct information about the fertilizability and analyze S-allele based genetic diversity among Korean apples, we investigated self-incompatibility genotypes by PCR and cross-pollination tests in field. As a consequence, S-genotypes of Korean apples were distributed within narrow genetic diversity as $S_1S_3$ for 'Hongro' and 'Saenara'; $S_1S_9$ for 'Gamhong' and 'Manbok'; $S_3S_5$ for 'Seokwang'; $S_3S_9$ for 'Sunhong', 'Seohong', 'Chukwang', and 'Hwahong'. Coupled with cross-pollination experiments in field, our results provide support for the view that apples are fully compatible when both of their S-loci differ and semi-compatible when they carry one different and one identical S-locus. Furthermore, the results of this study indicate that S-alleles have to be extended to various genotypes for Korean apple breeding.

• Journal of Plant Biotechnology
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• v.37 no.4
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• pp.408-413
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• 2010

The paper reviewed research status and outlook of genetic transformation in fruit trees in Korea. Genetic transformation has been long considered as an alternative technique overcoming limitation of conventional breeding and conducted since early 1990's. An efficient genetic transformation was established with major cultivars of apple, even in Fuji and Gamhong, and some transgenic apple plants have been transferred into the greenhouse for further analysis of gene expression. A few successes of genetic transformation have been reported and application to a variety of cultivars tried in citrus and kiwifruit. Successful genetic transformation has not been reported in the other fruit trees including grapevine, yet and it is considered being at the level of research. Those factors including replacement of antibiotics as a selective agent, use of transgenic rootstocks and manipulation of gene expression at proper parts and developmental stages have been prerequisites for the rapid commercialization of transgenic fruit plants.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.5
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• pp.637-643
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• 2010

For enhancement of apple productivity, the calcium fertilizers to increase the calcium content of fruit, and reduce the incidence of bitter pit in apples are applied. Crushed oyster shell contains a plenty of calcium carbonate, and a very small amount of boron, ferrous, and manganese. A field study was conducted to determine the optimum level of crushed oyster shell for soil nutrient management, and its effect on the induction of bitter pit in cultivar 'Gamhong' apple. The application of crushed oyster shell increased organic matter, available phosphate, and exchangeable cation concentration in soil. We found a significant positive correlation between soil pH, and application level of crushed oyster shell in both top, and subsoils. The incidence of bitter pit in apple fruit at the harvest stage was significantly higher in non treatment and calciummagnesium carbonate treatment than on over applications 4 Mg $ha^{-1}$ for crushed oyster shell. However, the optimum level of crushed oyster shell was 2 Mg $ha^{-1}$, especially considering the soil Ca content, soil pH, fruits weight, and yield. Our results show that the crushed oyster shell can be effective in restoring the soil nutrient balance, and inducing the bitter pit in apple fruit.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.655-658
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• 2011

A new cultivar 'Hongan' was originated from an artificial cross between 'Fuji' and 'Jonathan' carried out at National Institute of Horticultural & Herbal Science in 1993. The cultivar was preliminarily selected among the elite siblings for its high fruit quality in 2002. After regional adaptability test at five districts for subsequent four years as 'Wonkyo Ga-32', it was finally selected in 2006. 'Hongan' is characterized by the following. Optimum harvest time is late September. Shape of the mature fruit at 309 g on mean weight is globosity with a light red skin on a greenish yellow ground and yellowish white flesh. The fruit contains favorable total soluble solids at $13.7^{\circ}Brix$ and an acidity at 0.28%. Safe storage period for the fruit is 3 weeks at room temperature. It is resistant to Bitter rot. 'Hongan' also reveals a physiological cross compatibility with leading cultivars such as 'Gamhong' and 'Tsugaru' in addition to its maternal parent 'Fuji'. Tree topology is semi-spreading with vigorous growth habit.

• Journal of Bio-Environment Control
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• v.25 no.3
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• pp.184-192
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• 2016

This study was carried out to investigate the effect of temperature ($15{\sim}40^{\circ}C$) and the spraying plant growth regulators ($GA_{4+7}+BA$ and prohexadione-calcium) during full blooming on pollen germination and pollen tube growth of the commercial apple cultivars ('Fuji' and 'Tsugaru') and apple cultivars bred in Korea ('Chukwang', 'Gamhong', 'Hongan', 'Honggeum', 'Hongro', 'Hwahong', 'Hongso', 'Summer dream' and 'Sunhong'). Pollen germination and pollen tube growth were increased with increasing temperature from 15 to $25^{\circ}C$, but high temperature over $30^{\circ}C$ inhibit those. The apple cultivar bred in Korea that shows the highest value on pollen germination and pollen tube growth at over $30^{\circ}C$ was 'Sunhong'. The spraying $GA_{4+7}+BA$ increased pollen germination and pollen tube growth than control, but that effect was not show at $40^{\circ}C$. The spraying prohexadione-calcium was not affect to pollen germination and pollen tube growth. In conclusion, if the air temperature during full bloom of apple tree rises about $30{\sim}35^{\circ}C$, the spraying $GA_{4+7}+BA$ after artificial pollination will be good to increasing fruit set.

• Horticultural Science & Technology
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• v.31 no.6
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• pp.666-676
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• 2013

The study was carried out to examine the initial point of dormancy, breaking time of internal dormancy, and to find out the accumulated hours of low temperature (under $7.2^{\circ}C$ from $0.0^{\circ}C$ to $7.2^{\circ}C$) for bud-breaking. Over-all, the chilling requirement for breaking of internal dormancy in the commercial apple cultivars ('Fuji' and 'Tsugaru') and apple cultivars bred in Korea ('Hongro', 'Sunhong', 'Honggeum', 'Hongan', 'Hongso', 'Gamhong', 'Summer dream') at the Gunwi region for 4 years (from 2009 to 2012) was investigated. Also, the breaking time of internal dormancy in the field at the Gunwi region and the breaking time of dormancy if air temperature of Gunwi region rises $4^{\circ}C$ higher than the current one were investigated using the same data. The initial point of dormancy was set at the time when the lateral bud breaking did not occurred (when heading back cutting was done in the middle of terminal shoots). The occurrence of the breaking of internal dormancy was decided if the breaking of the terminal bud of bourse shoot occurred within 15 days or not in growth chamber. About 100 bourse shoots were collected by cultivar classification in early December every year and were stored at $5.0^{\circ}C$, and they were placed in growth chamber at one week interval. The chilling requirement of cultivars was expressed in accumulated hours in the field and in the growth chamber under $7.2^{\circ}C$ and $0.0-7.2^{\circ}C$ from the initial point of dormancy to the breaking time of internal dormancy. The results showed that the initial point of dormancy in selected cultivars could occur at the end of September. The breaking time of internal dormancy could occur from the end of January to the early of February. The accumulated hours under $7.2^{\circ}C$ for breaking of internal dormancy were 1,600-2,000 hours, while those of $0.0-7.2^{\circ}C$ were 1,300-1,800 hours. In comparing the different apple cultivars, the chilling requirement of the early flowering cultivars seemed lower than that of the late-flowering cultivars. Based on these results, if the air temperature of Gunwi region rises about $4.0^{\circ}C$ higher than the current one, the breaking time of internal dormancy will be delayed by 2-4 weeks.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.4
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• pp.252-269
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• 2017

This study was carried out to examine the base temperature to flowering and the average days to flowering by accumulated hours of low temperature ($5.0^{\circ}C$) or changing temperature after bud breaking. Over-all, the prediction of flowering time in the commercial apple cultivars ('Fuji' and 'Tsugaru') and apple cultivars ('Chukwang', 'Gamhong', 'Hongan', 'Honggeum', 'Hongro', 'Hongso', 'Hwahong', 'Summer dream', 'Sunhong') bred in Korea at the Gunwi region for 4 years (from 2009 to 2012) was investigated. Also, this study estimated the flowering time when the air temperature of Gunwi region rises at $5.0^{\circ}C$ was investigated using the same data. The range of accumulated hours of low temperature (chilling requirement) was from 0 hour to 1,671 hours, and the range of high temperature (heat requirements) to flowering after low temperature treatment was from $5.0^{\circ}C$ to $29.0^{\circ}C$. The treatments of changing temperature after bud breaking were classified as constant temperature treatment (control) and $5.0{\sim}10.0^{\circ}C$ elevation or descent treatments. The results show that the average days to flowering was longer with shorter accumulated hours of low temperature, and the average days from bud breaking to flowering of 0 hour treatment was longer about 2~4 weeks than that of 1,335~1,503 hours treatments. In comparing to apple cultivars, the all cultivars were not flowered under $10.0^{\circ}C$ after bud breaking, and the cultivars with low chilling requirements needed low heat requirements for flowering. The average days to flowering of treatments that the air temperature after bud breaking was controlled about $15.0^{\circ}C$ was shorter about 1~3 weeks than that of treatments was controlled about $10.0^{\circ}C$. In the treatment of changing temperature after bud breaking, the average days from bud breaking to flowering of temperature elevation treatment was shorter than that of constant temperature treatment. By use of these results, the base temperature to flowering of main apple cultivars in Korea was seemed to $10.0^{\circ}C$, and if the air temperature of Gunwi region rises about $5.0^{\circ}C$ than that of current, the flowering time was estimated to be delayed by 1 week.

• Korean Journal of Breeding Science
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• v.42 no.5
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• pp.525-533
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• 2010

In this study, random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) analyses were utilized for evaluation of genetic diversity of 34 Korean bred and introduced apple cultivars. Thirty-seven RAPD primers detected a total of 193 polymorphic bands (36.2%) with an average of 5.6. Twenty-six SSR markers generated a total of 112 alleles with an average 4.3 alleles per locus. Genetic diversity of 34 cultivars estimated by polymorphic information content (PIC) value ranged from 0.536 (CH03d12) to 0.952 (CH04c06) with an average of 0.843. By UPGMA (unweighted pair-group method arithmetic average) cluster analysis with 305 polymorphic bands, the apple cultivars were classified four groups by similarity index of 0.640. The 'Seokwang' was included in group I. Group II consisted of 12 cultivars which have 'Golden Delicious' in their pedigree, with the exception of 'Spur Earliblaze' and 'Jonathan'. Group III included 13 cultivars which have usually 'Fuji' in their ancestry and bud sport of 'Fuji' cultivars. Group IV consisted of 8 cultivars with 'Hongro', 'Gamhong', and 'Saenara'. Similarity values among the tested apple cultivars ranged from 0.529 to 0.987, and the average similarity value was 0.647. The similarity index was the highest (0.987) between 'Hwarang' and 'Danhong', and the lowest (0.529) between 'Seokwang' and 'Hwarang'. The genetic relationships among the 34 studied apple cultivars were basically consistent with the known pedigree.