Research Report키큰방추형 '후지'/M.9 사과나무의 영양생장, 생산성 및 과실품질 Abstract: Well-feathered (over 10 feathers) 'Fuji'/M.9 apple trees were planted at 3.0 × 1.0 m and trained to slender spindle with 2.5 m height or to tall spindle with 3.5 m height, and the vegetative growth, productivity, and fruit quality of two training systems were compared for 8 years. The canopy volume of the tall spindle trees surpassed that of the slender spindle trees 4 years after planting and was 25% larger than that of the slender spindle trees 5 years after planting. The accumulated yield over 8 years for the tall spindle system was 14% higher than that of the slender spindle system. Alternate bearing and incidence of marssonina blotch were observed in both treatments after 5 years of planting. There was often vegetative imbalance in the trees however, the degree of yield loss and vegetative imbalance of the tall spindle trees was lower than those of the slender spindle trees. Soluble solid content and fruit red color of the tall spindle trees were higher than that of the slender spindle trees in 5 year after planting, resulting from increased light penetration in the canopy due to even distribution of lateral branches and from fruit bearing in different height locations of the trees. In conclusion, increasing the tree height to about 3.5 m using slender spindle 'Fuji'/M.9 apple trees planted with over 333 trees per 10a led to better light penetration, yield and fruit quality compared to a conventional wide training system with the slender spindle.Additional key words: accumulated yield, canopy volume, feather location in canopy, Malus domestica Borkh., slender spindle *Corresponding author: tmyoon@knu.ac.kr † These authors contributed equally to this work.※

Abstract. This study investigated the influence of seasonal incidence and defoliation degree caused by Marssonina blotch (Diplocarpon mali Harada et Sawamura) on shoot growth and fruit quality of 'Fuji'/M.9 apple tree. The occurrence of marssonina blotch in Gunwi region was observed from the mid of July 2009, and percentage of defoliation was about 10% in the end of October. In 2010, that started in the early of June. By the end of September, percentage of defoliation was 20% and it reached 50% in late October. Secondary growth of terminal shoot in 2010 was three times as much as that in 2009. In 2009, the soluble solid contents and the red color (hunter a value) during fruit maturation increased to 13.8 °Brix and 16.2, respectively. In 2010, the soluble solid content during fruit maturation remained in the 12.1-12.6 °Brix range after early October, and the red color began to increase after the end of September when the percentage of defoliation was 20%. As for fruit quality by defoliation degree, the red color decreased when defoliation percentage of bourse shoot at the end of October was more than 30%. Fruit weight and soluble solids also decreased when defoliation percentage was more than 50%. Fruit length and diameter of over 30% defoliation treatments begun to decrease after the middle of August, compared with those of under 30% defoliation treatment. Photosynthetic rate of the leaves that was located at the secondary growth of bourse shoot was similar to that of leaves which was located at the middle of bourse shoot. However, the size and the soluble solid content of fruit were not affected by photosynthesis activities of bourse shoot leaves which was develop in the secondary shoot growth.

Nutrient content assessment of plant tissues is widely performed by farmers to determine the appropriate amount of fertilization to use for their crops. A nondestructive leaf chlorophyll meter is one of the most commonly used devices for performing field assessments of the nutrient status of leaves. However, it is challenging to use a chlorophyll meter to assess the nutritional status of perennial plants, such as the apple (Malus ×domestica) tree, because of the difficulty estimating nitrogen (N) during the entire growing period. We compared the chlorophyll meter readings with leaf nutrient profiles collected from young ‘Arisoo’/M.9 apple trees throughout the growing period. A significant positive correlation between the chlorophyll meter readings and leaf N content was found from May to August during the midseason. Regression analysis indicated that the best sampling time for predicting the foliar N content of apple tress is from late June to late July. This result suggests that a reliable leaf N assessment can be performed in a rapid, nondestructive way in apple orchards.

This study was conducted to elucidate the influence of prohexadione-calcium (Pro-Ca) application on shoot growth and fruit quality in 'Fuji'/M.9 mature apple trees. Pro-Ca was applied at concentrations ranging from 100 to 400 mg･L -1 one time at petal fall (PF; 5-10 cm terminal shoot growth) to the whole canopy of the tree, or at 100, 125, 150 mg･L -1 concentrations two times, at PF and then 4-8 weeks after PF. Pro-Ca treatment generally reduced mean shoot growth, with its effect being proportional to the application rate. Pro-Ca at 400 mg･L -1 significantly reduced the shoot growth by 15-22% compared to the control, while its effect was not significantly different from Pro-Ca 200 mg･L -1

Abstract. 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°C from 0.0°C to 7.2°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°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°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°C and 0.0-7.2°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°C for breaking of internal dormancy were 1,600-2,000 hours, while those of 0.0-7.2°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°C higher than the current one, the breaking time of internal dormancy will be delayed by 2-4 weeks.