Hun-Joong Kweon

Impacts of Urban High Temperature Events on Physiology of Apple Trees: A Case Study of `Fuji`/M.9 Apple Trees in Daegu, Korea

In this study, we examined the effect of high temperature of urban area on the physiological response of apple tree including the photosynthesis, shoot growth, and fruit quality of ‘Fuji’/M.9 apple trees planted at Daegu urban area (DUA) and Gunwi rural area (GRA) for 2 years (2009-2010). During the apple growing season (April-October), the average air temperature of DUA was about 3.0 o C higher than that of GRA and the total rainfall of DUA was 130 mm more than that of GRA. During fruit enlargement stage (June-August), the number of days that recorded daily mean temperature of over 30 o C were ten on DUA in 2010, but there was no day when such temperature was experienced in 2009. Average air temperature of DUA during the maturation stage (September-October) was 19.8 o C, which was 4.0 o C higher than that of GRA. The higher temperature of over 30 o C during fruit enlargement stage decreased the photosynthetic rate, shoot growth, fruit weight, and soluble solid content of ‘Fuji’/M.9 apple tree. The moderate temperature of about 20 o C during maturation stage increased the photosynthetic rate and soluble solid content of ‘Fuji’/M.9 apple tree, but decreased fruit red color. In regional comparison with GRA, photosynthetic rate of DUA was changed from lower before rainy season to higher after rainy season. Fruit weight was higher in DUA than that of GRA. However, fruit weight between DUA and GRA did not show the difference when accumulated days that recorded daily maximum temperature over 35 o C of DUA was increased. Compared to the GRA, soluble solid content of DUA was higher, but fruit red color of DUA was less. These results indicate that the poor red coloring is the most problematic in ‘Fuji’/M.9 apple tree by global warming and urbanization.

Influence of Low Temperature and Chilling Time on Freezing Hardness of Apple Dwarf-rootstocks and Main Cultivars in Korea

This study was conducted to find out the freezing hardness of apple tree as influenced by dwarfrootstocks, cultivars, and low temperature treatments. The dwarf-rootstocks used were M.9 and M.26, and three cultivars used were early-maturing `Tsugaru`, mid-maturing `Hongro`, and late-maturing `Fuji`. Chilling temperatures were applied from to . Checking points of apple tree for freezing hardness were rootstock, trunk, feather, floral bud and foliar bud. Investigations were evaluated by the measure of water loss, electrolyte leaching, and sprouting. The results did not show the differences in water loss, electrolyte leaching, and sprouting by dwarf-rootstocks. Water loss of `Fuji` was lower than that of `Tsugaru` and `Hongro`, but sprouting ratio of `Fuji` was higher than that of `Tsugaru` and `Hongro`. Water loss and electrolyte leaching increased as treated by lower temperature, while sprouting ratio decreased. In treatment, sprouting of rootstock and trunk part were higher than that of feather, while sprouting of floral bud was lower than that of foliar bud. Sprouting of bourse shoot at the accumulated low temperature in terms of per day was 100% in the 28 days, and sharply decreased about 50% in the 35 days. In conclusion, there were no differences in freezing hardness between M.9 and M.26, but freezing hardness of late-maturing cultivar was tended to stronger than that of early-maturing and mid-maturing cultivars. Freezing hardness of floral bud was extremely weak .

Effect of RED and FAR-RED LEDs on the Fruit Quality of 'Hongro'/M.26 Apple

Abstract BACKGROUND: As improved LEDs (Light Emitting Diode) industry and decreased the price of LEDs in Korea, some farmers try to using the RED LEDs in green house and open field to increase the production of crop under bad weather condition. The aim of this study is to find out the effect of RED and FAR-RED LEDs lighting on the fruit quality of twelve-year old ‘Hongro’/M.26 apple during night after sunset. METHODS AND RESULTS : FAR-RED (730nm, 2 and 4 hour) and RED (620nm, 2 and 4 hour) with 20 LED/PCB were treated in orchard for 16 weeks from June 10 to October 10 in 2009 and 2010 with control as an comparison. In our experiments, leaf weight was significantly higher in RED LEDs than control, tended to be decreased as times of FAR-RED lighting increased. Fruit weight was increased more in RED LEDs than control in 2009 and 2010, but decreased in FAR-RED lighting compared to control in 2010. Firmness and Hunter’s a value of fruit were increased in FAR-RED lighting with 2 and 4 h than control. Soluble solid contents were higher in 2 h RED and 2, 4 h FAR-RED LEDs compared to control in 2009, there was no significant difference in 2010. Acid contents were no difference among the treatments.

Influence of Elevated CO 2 and Air Temperature on Photosynthesis, Shoot Growth, and Fruit Quality of `Fuji`/M.9 Apple Tree

This study was conducted to find out the influence of elevated atmospheric CO2 concentrations and air temperature on photosynthesis and fruit quality of ‘Fuji’/M.9 apple trees and to investigate these to the effects of climate change during the last four years (2009-2012). The treatments employed were: ‘Ambient’ (ambient temperature + ambient CO2 concentration); ‘High CO2’ (ambient temperature + elevated CO2 concentration); ‘High Temp.’ (elevated temperature + ambient CO2 concentration); and ‘High CO2 + High Temp.’ (elevated temperature + elevated CO2 concentration). The elevated temperature plots were maintained at 4 o C higher than ambient air temperature, while the elevated CO2 plots were maintained at 700 µmol·mol �1 . Annual treatment period was applied from end of April to beginning of November for four years. Results showed that elevated CO2 decreased stomatal conductance and leaf SPAD value, but increased photosynthetic rate, intercellular CO2 concentration (Ci), and starch content of mesophyll tissue. In the vegetative growth, elevated temperature increased total number of shoot and total shoot growth per tree, but elevated CO2 decreased average shoot length. In the fruit quality, elevated CO2 increased soluble solid content, fruit red color, and ethylene production. In conclusion, elevated CO2 increased photosynthetic rate of apples during the early growth, but effect of increased photosynthetic rate due to elevated CO2 was decreased during latter growth stage. Elevated temperature, on the other hand, tended to decrease photosynthetic rate of apples during the early growth, but that tended to increase during latter growth stage. Both elevated CO2 and temperature tended to decrease the degree of decreased photosynthetic rate due to each factor.

Effect of Exposed Length of Rootstocks on the Occurrence of Bitter Pit and Tree Vigor of ‘Gamhong’/M.26 Apple Cultivar

‘Gamhong’ apple cultivar which was bred by National Institute of Horticultural and Herbal Science, has high sugar contents, large types of fruit and mid-season types of cultivar. However, ‘Gamhong’ apple tree is very sensitive cultivar to bitter pit. Therefore, many farms have not solved the problems on bitter pit to cultivate ‘Gamhong’ apple tree. This study was carried out to find out the exposed length of rootstocks on the occurrence of bitter pit and fruit quality of ‘Gamhong’/M.26 apple tree and seek the ideal cultivation strategy to decrease bitter pit to cultivate it. For this research, ten-years-old ‘Gamhong’/M.26 apple trees were used. The difference among the treatments of the exposure of rootstock of RL (5 cm), RM (15 cm) and RH (20 cm) from the soil surface was observed with 4 repetition from 2010 to 2011. Decreased exposure of rootstocks resulted in more vigorous growth, taller height, and greater number of shoots. N and K/Ca of RH was tend to be lower than RM and RL, whereas as the exposure of rootstock decreased, fruit weight and bitter pit increased. Therefore, occurrence of bitter pit in RH was significantly lower than that of RM and RL treatment and fruit weight also decreased. There was no difference on nutrient contents of leaf and the fruit quality by the exposed of rootstock in ‘Gamhong’ M.26 apple tree. To reduce the occurrence of bitter pit, it may be helpful to keep the optimum exposure of rootstock within 20 cm from the soil surface.

Effect of Flower and Fruit Thinner on Fruit Set and Fruit Quality of ‘Gamhong’ Apples

This study investigated the effects of flower and fruit thinning agents on fruit set and harvested fruit quality attributes in ‘Gamhong’ apples. Lime sulfur, MaxCel (1.9% BA), and Fruitone (3.5% NAA) were applied either at post-bloom or fruitlet stages to mature ‘Gamhong/M.9’ trees. In 2011, the numbers of fruits per cluster in terminal flowers were 1.74, 0.82, and 1.15 for the control, lime sulfur, and Maxcel (applied at 10-mm fruit stage) treatments, respectively. The percentages of single fruit per cluster were 36.0, 47.9, and 48.7% for the control, lime sulfur, and Maxcel (10 mm) treatments, respectively, while the percentages of clusters with three fruits per cluster were 22.9, 1.4, and 5.8%. In lateral flowers, fruit numbers per cluster were 1.20, 0.36, and 0.50 for the control, lime sulfur, and Maxcel (10 mm) treatments, respectively. In 2012, all the thinning treatments showed a positive effect on flower and fruit thinning, compared with the control. Moreover, the treatment with thinning agents did not affect fruit quality. Overall, the results suggest that a single application of flower or fruit thinning agents would be sufficient, rather than the mixed application of thinning agents, based on the observed decrease in fruit setting. Additional key words: benzyladenine, fruit set ratio, lateral flowers, lime sulfur, naphthaleneacetic acid, terminal flowers Received: August 5, 2015 Revised: October 13, 2015 Accepted: January 25, 2016 Copyrightc2016 Korean Society for Horticultural Science. 본 연구는 농촌진흥청 공동연구사업(PJ01048102) 의 지원에 의해 수행되었음. Korean J. Hortic. Sci. Technol. 34(1):24-31, 2016 http://dx.doi.org/10.12972/kjhst.20160006 pISSN : 1226-8763 eISSN : 2465-8588 적화제 및 적과제가 ‘감홍’ 사과의 착과와 과실 품질에 미치는 영향 Korean Journal of Horticultural Science & Technology 25 서 언 ‘감홍’ 사과(Malus×domestica Borkh.)는 국립원예특작과학원에서 1981년에 ‘Spur EarliBlaze’에 ‘Spur Golden Delicious’ 를 교배하여 1992년에 육성된 중만생종 품종이다(Shin et al., 1993). ‘감홍’ 과실의 특성을 보면 과실의 크기는 400-450g으로 대과종이고, 수확기는 10월 초ᆞ중순이며, 과즙의 당도는 15°Brix 이상, 산도는 0.40% 정도로 식미가 매우 우수한 품종으로 평 가받고 있다(Shin et al., 1993). 따라서 최근 국내 소비시장에서 인기가 높아지면서 재배면적이 점차 확대되고 있는 실정이다. 사과의 경우 격년결실 방지와 적정 착과 및 과실 비대 촉진을 위하여 적과작업을 필수적으로 실시하고 있다(Childer et al., 1995; Dennis, 2000; Kim and Guak, 2010; Kook et al., 2009; Yoo et al., 2014). 그러나 최근 국내 농촌에는 고령화에 따른 노 동력 부족현상이 심화되고 있고 그에 따른 인건비 상승이 심각한 문제로 대두되고 있다. 우리나라의 경우 사과원 경영에 있어 노동력 투입비율을 보면 적과 작업이 총 노동투입의 12-16%를 차지하고 있으며(Park et al., 1998, Yoo et al., 2014), 일본의 경 우 우리나라보다 높은 24%에 달한다고 한다(Koike and One, 1998). 그러므로 인력 적과를 대체할 수 있는 약제를 이용한 적화 및 적과 기술개발이 필요하다(Jang et al., 1998). 지금까지 사용되어온 적과제인 Carbaryl은 적과 효과가 있지만(Batjer and Billingsley, 1964) 화분 매개곤충, 특히 꿀벌을 죽 이는 부작용으로 사용에 제한을 받고 있어 이를 대체할 적과제의 필요성이 대두되고 있다(Dennis, 2000). 최근 호주, 미국, 한 국 등에서 사과나무의 적화제로 석회유황합제(Lime sulfur)와 ammonium thiosulfate(ATS)를, 적과제로 6-benzyladenine(BA) 와 naphthaleneacetic acid(NAA)를 이용하고 있다(Bound et al., 1997; Greene and Autio, 1989; Greene et al., 1992; Guak et al., 2002; Kim and Guak, 2010; Robinson et al., 1998; Stover et al., 2001; Wismer et al., 1995). 국내에서는 ‘후지’와 ‘홍로’ 사 과에서 ATS, BA, NAA 등이 적과제로서 효과가 있고, 익년 개화율에도 영향이 없는 것으로 보고되어 있다(Guak et al., 2002; Kim and Guak, 2010; Yoo et al., 2014). 그러나 ‘감홍’ 사과에 대한 적화제 및 적과제의 효과에 대한 연구는 없는 실정이다. 따라서 본 연구는 ‘감홍’ 품종을 대상으로 화학적 약제 적용이 과실의 착과에 미치는 영향을 구명함으로써 노동력을 절감할 수 있는 적화제 및 적과제의 실용화 가능성을 검토하고자 실시되었다.

Influence of Dormancy Level and Carbon Concentration on Freezing Hardiness in Bourse Shoot of `Fuji` Apple Tree

This study was conducted to find out influence of dormancy level and carbon concentration on freezing hardiness in bourse shoot of ‘Fuji’ apple tree. Bourse shoot of ‘Fuji’ adult apple tree grafted on M.26 and M.9 rootstocks were used as experimental materials. Dormancy levels of bourse shoot were categorized according to the periods as follows the internal dormancy (late January), the early days after internal dormancy breaking (early February), the late days after internal dormancy breaking (late February), the bud break (late March), and the full bloom (late April). Chilling temperatures with bourse shoot were ranged from 0 to –40oC. Also, the freezing hardiness according to carbon concentrations were investigated on ‘Fuji’/M.9 apple tree that defoliated severely by Marssonina blotch (defoliation) and that of below the average 20 cm in shoot length through heavy crop load (weakness). Results showed that freezing hardiness of bourse shoot may become weaker after internal dormancy breaking. There was no differences in the carbon concentration of bourse shoot of ‘Fuji’ apple tree grafted on M.9 and M.26, so may be resulted in no difference in freezing hardiness both of bourse shoot grafted on M.9 and M.26 rootstock. Carbon concentration in bourse shoots with weakness and C/N ratio in bourse shoots with defoliation were lower than that of healthy. It may be shown that the freezing hardiness of defoliation and weakness were weaker than that of healthy.