• Korean Journal of Environmental Agriculture
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• v.41 no.3
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• pp.199-205
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• 2022

BACKGROUND: The freezing injury by pruning can be reduced by suspending pruning work when severe cold weather (-23 to -49℃) is forecast. Minimum air temperature of the study area, Gunwi region at February 3, 2012 was -21.9℃, and the subzero temperature continued until April 8, 2012. This study was conducted in two years to investigate the effect of delaying winter pruning until full bloom on shoot growth and fruit quality of 'Fuji'/M.9 apple trees. METHODS AND RESULTS: The time of pruning were March 26 for dormant, April 3 for bud break, and May 2 for full bloom. The winter pruning at full bloom significantly reduced fruit weight for two years compared with the control (winter pruning at dormant), and shoot growth was reduced only in the following year. There was no significant effect of delaying winter pruning at bud break on soluble solid content, fruit red color, return bloom, and pruning weight for two years compared with the control. CONCLUSION(S): These results indicated the delaying winter pruning at bud break of 'Fuji'/M.9 apple tree did not offer any disadvantage over comparable dormant pruning, since the fruit quality was not affected. The delayed pruning at full bloom resulted in decreased fruit weight, though shoot growth, fruit quality, and return bloom were not affected by the delayed pruning. So, the delayed pruning should be considered carefully only for the fruit tree orchards in diseases.

• Korean Journal of Environmental Agriculture
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• v.38 no.3
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• pp.145-153
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• 2019

BACKGROUND: The 'Gamhong' cultivar, middle season apple with big fruit size and high soluble solid content, has been bred in Korea. However, it was hard to cultivate the cultivar in Korea by serious bitter pit. The relationships between shoot growth, fruit size, and bitter pit may be affected by crop load. This study was conducted for 2 years (7~8 years after planting) to investigate vegetative growth, fruit quality, bitter pit incidence, return bloom, and gross income for optimum crop load of 'Gamhong'/M.9 adult apple tree. METHODS AND RESULTS: The crop load was assigned to 4 different object ranges as follow: 45~64, 65~84, 85~104, and 105~124 fruits per tree. The vegetative growth, average fruit weight, percentage of fruits heavier than 375 g, soluble solid content, and return bloom increased significantly at the crop load range of 45~64 fruits. However, the lowest total gross income per tree may have been caused by the highest bitter pit incidence and the lowest yield per tree in any other crop load range. The total gross income and yield per tree increased significantly at the crop load range of 105~124 fruits and return bloom dropped to 40%, and hence it was possible to occur biennial bearing. It was 85~104 fruits that biennial bearing did not occur and total gross income was as high as the crop load range of 105~124 fruits. Also, the yield of high grade fruits per tree, with fruit weight of 400~499 g and none bitter pit on fruit surface, was highest at the crop load range of 85~104 fruits, compared to other crop load range. CONCLUSION: In considering fruit size, bitter pit incidence, return bloom, and gross income, the optimum crop load range of 'Gamhong'/M.9 adult apple tree in high density orchard was 85~104 fruits per tree.

• Journal of Bio-Environment Control
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• v.30 no.4
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• pp.342-350
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• 2021

This study was conducted to investigate the effect of time of hand-thinning on vegetative growth, bitter pit incidence, fruit quality, and return bloom in 'Gamhong'/M.9 apple trees. The time of hand-thinning were 3, 5, 7 and 9 weeks after full bloom, and the primary thinning (leaving only the king fruit on cluster) and secondary thinning (adjusting crop load) were conducted at the same time. The time of hand-thinning was correlated to the vegetative growth, average fruit wight, yield, soluble solids content, bitter pit incidence, and return bloom, negatively, and to the yield of middle grade fruits (fruit weight was 250-299g and none pit on fruit surface) per tree, calcium contents of leaves, and fruit red color, positively. There was no significant effect of time of hand-thinning on fruit firmness, titratable acidity, and total incomes per tree. In conclusion, if the time of hand-thinning of 'Gamhong'/M.9 apple tree was completed at 9 weeks after full bloom, it could produce about 300g of high-quality fruit without bitter pit.

• Journal of Bio-Environment Control
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• v.25 no.2
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• pp.133-137
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• 2016

'Sinano Sweet' apple trees were defoliated at intervals of a month from May to October to simulate damage occured by hail and typhoon in Korea, accordingly fruit yield, reserve accumulations and return bloom were investigated. As the more severe defoliation degree was and earlier defoliation time was, fruit weight and fruit yields were more decreased. Fruit weight and yields of 30% defoliated trees, regardless of the defoliation time, showed no significant difference with those of control. Because carbohydrate contents of the 2-year old branches defoliated before August were even lower than those of branches defoliated after September, it was considered that defoliation time is more effective on the carbohydrate content than defoliation degree. Among the trees defoliated before August, 50% defoliated trees at August contained the lowest carbohydrate by 50% of control. Time and degree of defoliation had an effect on the number of flower buds following year. The number of return bloom in trees defoliated from May to July was decreased by delay of defoliation time and was the lowest in trees defoliated at July. On the other hand, it was not have a significant different between control and trees defoliated since August. Relationship between the number of return bloom and carbohydrate reserves showed positive correlation. As a result, it is considered that fruit thinning, when defoliation occurred in the growing season, needs for strengthening the sink function of remained individual fruit effect on fruit enlargement and for increaseing the carbohydrate reserve effect on return bloom.

• Horticultural Science & Technology
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• v.31 no.1
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• pp.38-49
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• 2013

Prohexadione-calcium (Pro-Ca), ethephon and transient water stress were evaluated in a factorial design, as potential inhibitors of early-season shoot growth of high density orchard management of apple (Malus domestica Borkh.) trees. In the experiment, water stress was imposed to one-half of the 7-year-old 'Golden Delicious'/M.9 apple trees in each of 5 blocks, by stopping irrigation for 3 weeks between 35 and 56 days after full bloom (AFB). Within each whole unit, the following Pro-Ca and ethephon treatments were randomly allocated at $2{\times}2$ factorial: a) 0 or 250 $mg{\cdot}L^{-1}$ a.i. Pro-Ca applied at 28 days AFB and b) 0 or 300 $mg{\cdot}L^{-1}$ a.i. ethephon applied twice (35 and 71 days AFB). All trees were hand thinned to king flowers prior to treatments. Vegetative shoot growth was markedly reduced by Pro-Ca, with its effect being obvious within 14 days after application, while ethephon and water stress treatments were less effective. Pro-Ca had no effect on fruit set and yield but slightly increased fruit size. Ethephon substantially reduced the fruit size and yield but had no effect on fruit set. Water stress reduced fruit set, fruit size and yield. With regard to fruit quality, Pro-Ca did not influence fruit shape, flesh firmness and soluble solids contents (SSC) but slightly reduced titratable acidity. Ethephon had no effect on fruit shape but increased firmness, SSC and acidity, while water stress did not influence these fruit quality attributes. Dry weight of dormant spur buds was reduced by both Pro-Ca and water stress, while increased by ethephon. The larger dormant buds led to the larger spur flowers at the tight cluster stage the following spring. Return flowering was promoted only by ethephon, especially on previous season's shoots. There were no significant interactions between Pro-Ca and ethephon or water stress on most variables observed in this study.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.328-334
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• 2022

BACKGROUND: The low temperature at flowering period break the balance between vegetative and reproductive growth of apple tree. Summer pruning has been used to control vegetative growth. So, this study was conducted to investigate the effect of summer pruning time on shoot growth and fruit quality of 'Fuji'/M.9 apple trees damaged by the low temperature at flowering period. METHODS AND RESULTS: The following treatments were applied to tree : a) control (no summer pruning), b) pruned 26 June, c) pruned 30 July, d) pruned 28 August, and e) pruned 26 September. The summer pruning significantly increased light penetration and fruit red color by reducing the total shoot growth compared with control. And the summer pruning control the outbreak of apple valsa canker. But the summer pruning at the end of June increased regrowth of shoot and pruning weight compared with the summer pruning at the end of August. The summer pruning at 30 July had the highest fruit weight, but return bloom was the highest in the summer pruning at 28 August. CONCLUSION(S): These results indicated the optimum summer pruning time of 'Fuji'/M.9 apple trees damaged by the low temperature at flowering period were the end of August.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.531-538
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• 2011

This study was carried out to investigate the influence of defoliation by Marssonina blotch (Diplocarpon mali Harada et Sawamura) on vegetative growth and fruit quality in 'Fuji'/M.9 apple tree. Soluble solid contents decreased when the defoliation percentage by Marssonina blotch was over 10% before the end of September, and fruit weight decreased when percentage of defoliation was over 30%. Fruit red color and starch contents tend to decrease as percentage of defoliation near the fruit increased. Return bloom, fruit weight, and shoot growth the following year tend to decrease as percentage of defoliation increased. Photosynthetic rate of healthy leaves in bourse shoot during the end of September was maintained about $10{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, effects in increasing fruit growth and soluble solid contents after the end of September. Photosynthetic rates for the damaged leaf, damaged area was over 50% on the leaf surface, while 30% of the photosynthetic rates of healthy leaf are without damage applied with Marssonina blotch at the end of September. The results show that the decrease of fruit quality in defoliation treatments may be caused by the decrease of starch contents in fruit, and that was caused by the photosynthetic rates of leaves near fruit was decreased by Marssonina blotch in the wake of August.

• Horticultural Science & Technology
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• v.33 no.1
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• pp.1-10
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• 2015

This study was conducted in three years (7-9 years after planting) to investigate vegetative growth, yield, fruit quality, and return bloom for optimum crop load based on different planting densities of adult 'Fuji'/M.9 apple trees. As plant materials, 'Fuji'/M.9 apple trees planted at $3.5{\times}1.5m$ (190 trees per 10 a), $3.5{\times}1.2m$ (238 trees per 10 a), and $3.2{\times}1.2m$ (260 trees per 10 a) spacing and trained as slender spindles were used. The crop load was assigned to five different object ranges as follows: 55-64, 65-74, 75-84, 85-94, and 95-104 fruit per tree. TCA increment, total shoot growth, return bloom, yield per tree, and yield efficiency tended to increase as planting density decreased, and fruit weight and soluble solid content tended to increase as the object range of crop load decreased. Fruit red color tended to increase as shoot growth decreased. For apple trees planted with 238 trees and 260 trees per 10a, biennial bearing occurred when the crop load was over 85-94 and 75-84 fruits, respectively. However, biennial bearing did not occur when the crop load was 95-104 fruits in apple trees planted with 190 trees per 10a. Accumulated yield tended to increase as planting density and crop load increased, but that of biennial bearing did not show such a difference. Based on our results, optimum crop load recommendations are to set 95-104 fruits per tree in 'Fuji'/M.9 mature apple trees planted at 190 trees per 10a, 75-84 fruits per tree at 238 trees per 10a, and 65-74 fruits per tree at 260 trees per 10a.

• Horticultural Science & Technology
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• v.28 no.4
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• pp.552-560
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• 2010

$GA_{4+7}$+BA, a plant growth regulator for induction of feathering in young apple tree and increasing fruit size, was applied by various methods on 'Gala'/M.9 apple trees in high density orchard for 4 years to investigate its effect on fruit and shoot growth. $GA_{4+7}$+BA($80-300mg{\cdot}L^{-1}$) increased fruit length, fruit weight, and L/D ratio regardless of application methods, but it did not affect soluble solid content, acidity, leaf area, and chlorophyll. Seed number was not affected by $GA_{4+7}$+BA application, however, more immature seeds was observed in treated 'Gala' fruit. Shoot growth was increased when spraying $GA_{4+7}$+BA at tree crown but not affected when spraying at fruit directly. More significant fruit growth was observed when $GA_{4+7}$+BA was applied on the fruits between late of May and early of June when fruit cell division ended; however, high concentration of $GA_{4+7}$+BA resulted in lower fruit storability because of lower firmness. Hence, more attention should be paid when applying high concentration of $GA_{4+7}$+BA to small sized fruit cultivars like 'Gala'.