Moo-Yong Park

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.

Influence of Air Temperature during Midsummer on Fruit Sunburn Occurrence in 'Fuji'/M.9 Apple Tree

This study was carried out to investigate the effects of air temperature during midsummer on sunburn occurrence that had some problems recently on `Fuji`/M.9 planting system in Korea. There was a positive relationship between sunburn incidence and accumulated days with high air temperature over , or accumulated total quantum per day. `Fuji`/M.9 apple trees with relatively open canopies, compared to `Fuji`/M.26, were more susceptible to sunburn injury because the fruit was more exposed to sunlight. In `Fuji`/M.9 apple trees, those that were poor in vigor or with short bourse shoot length were more susceptible to sunburn injury. Sunburn incidence was affected by neither regions nor row orientations. Sunburn was observed most often on the fruits on the south and west sides of the trees. The reason was due to high skin temperature of the fruits reaching under full sunlight.

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.

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.

Effects of Microspraying of Water and Coating by White Materials on Fruit Sunburn Occurrence for `Fuji`/M.9 Apple Tree

This study was carried out to compare and analyze control methods of the sunburn occurrence that affected `Fuji`/M.9 planting systems in Korea from 2001 to 2003. It is very important to control temperature of the surface of fruits, because sunburn may occur when the temperature of fruit surfaces reaches due to high air temperature and sunlight during growing periods. As control methods of the sunburn occurrence, white coating materials such as or kaolin were applied four times at two-week intervals from late June, and microspraying of water was conducted when air temperature was over from late July to mid-August. Both methods were effective for preventing the sunburn occurrence and improving fruit quality by decreasing peel`s temperature of fruits and increasing photosynthesis.

Influence of Air Temperature during the Growing Period on Water Core Occurrence in `Hongro` Apple Cultivar and the Mitigation Technique

`Hongro` is one of the important mid-season apple cultivars bred in Korea. The recent occurrence of water core in Hongro and the consequent problems motivated this study. The objectives of our study were to investigate the influence of air temperature during the growing period on water core occurrence in Hongro and to provide methods to mitigate its impact. Based on our field experiments for three years, the results indicated that the occurrence of water core disorder was due to the prolonged exposure to high temperature () of > during the ripening period. The rates of occurrence of water core disorder were higher in the fruit whose weight was more than 300g or those located outside the tree canopy and thus exposed to stronger solar radiation. In terms of mitigating the water core occurrence, the application of spraying four times from late July to August was effective. Furthermore, between 1 and 15 August when the rate of occurrence was high with (from 3:00 to 5:00 p.m.) >, the micro-water sprinkling for 30 minutes starting at 6:00 p.m. with a supplementary spray conducted two hours after the first application drastically reduced the water core occurrence.