Young-Eel Moon

Plant growth and fruit quality as affected by canopy locations in ‘Shiranuhi’ mandarin

Fruit quality (soluble solids and acidity) and growth properties of fruiting branches in different canopy positions (upper, middle, and lower) of ‘Shiranuhi’ mandarin [(C. unshiu × C. sinensis) × C. reticulate] trees were determined during fruit maturation. Length, diameter, and number of leaves per fruiting branch increased in order from the upper, through the middle, to the lower parts of the canopy. Fruit diameter, fruit weight, pulp weight and pulp thickness were also highest in the upper part. Transverse sections of stem end protrusions in fruit from the upper, middle, and lower parts of the tree canopy were 37.3 ± 2.3 mm, 33.2 ± 0.2 mm and 32.1 ± 0.4 mm, respectively. Soluble solid content increased during fruit maturation at all locations within the canopy and was highest in the upper part. Likewise, acid content decreased with fruit maturity and was lowest in the lower part. These results suggested that harvesting be staggered starting with fruit from the upper part of the canopy as part of crop management in ‘Shiranuhi’ mandarin for direct effect on fruit quality.

Effect of Scion Root Occurrence on the Flowering, Fruit Quality and Yield of 'Shiranuhi' Mandarin Hybrid in Plastic Film House

As most of citrus, shiranuhi mandarin ((Citrus unshiu × C. sinensis) × C. reticulata) mainly use the trifoliate orange (Poncirus trifoliata) as its rootstock which has dwarf and cold hardness in Korea. However, recently, scion root was observed in ‘Shiranuhi’ mandarin tree grafted onto the trifoliate orange. This study was carried out to find out effects of scion root occurrence on the fruit quality, flowering and yield of shiranuhi mandarin. For the experiment, we selected six farmers who have outbreak of scion root in their Shiranuhi mandarin orchards and surveyed the difference of fruit quality of shiranuhi mandarin hybrid between scion root and control (trifoliate orange root). In the results, flowering was severely decreased in scion root trees compared to control. As a result of survey of 174 Shiranuhi mandarins, 160 trees were proved to be scion root, and had less flowering. Fruiting of scion root also severely dropped compared to control and thus, yields of scion root (6.4kg) reduced by 24% compared to control (26.7 kg). The fruit size, weight and soluble solid contents of scion root were significantly reduced, but there were no differences in acid contents and coloring of fruit. From the results, we concluded that scion root had negative influence on flowering, fruit size and the yields of Shrinanuhi mandarin hybrid.

Effect of Foliar Application of GA 3 on the Flower Bud Formation and Fruit Quality of Satsuma Mandarine (C. unshiu Marc. cv. Miyagawa)

Effect of Foliar Application of GA3 on the Flower Bud Formation and Fruit Quality of Satsuma Mandarine (C. unshiu Marc. cv. Miyagawa) Seok-Beom Kang, Young-Eel Moon, Seung-Gab Han, Yong-Ho Kim, Chi-Won Chae and Young-Hun Choi (Citrus Research Station, National Institute of Horticultural and Herbal Science, RDA, Seogwipo, 699-946, Korea, Agricultural Research Center for Climate Change, National Institute of Horticultural and Herbal Science, RDA, Jeju, 690-150, Korea)

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 Foliar Application of Gibberellic Acid and Machine Oil Emulsion Mixture on Flowering and Fruit Quality of Satsuma Mandarin (C. unshiu Marc. cv. Miyagawa) Cultivated on Open Fields

In satsuma mandarin (C. unshiu Marc. cv. Miyagawa), alternate bearing is frequently occurred. It is very difficult to control and maintain the optimum production because satsuma mandarin is a very sensitive citrus cultivar. We carried out the experiment to find out the effects of foliar application of gibberellic acid (GA₃) and machine oil emulsion mixture on flowering and fruit quality of satsuma mandarin grown on open field. The treatments were composed of control (no application), GA₃ (25, 50 and 100 mg?L -1 ), machine oil emulsion 100 times and mixture of GA₃ (25 and 50 mg?L -1 ) with machine oil emulsion 100 times on 16 year-old ‘Miyagawa’ satsuma mandarin on December 30, 2012. Foliar application of GA₃ during winter season led to a reduction of the flowering in the following year. GA₃ decreased flowering in dose dependant manner. However, application of GA₃ and machine oil emulsion (100 times-diluted mixture) inhibited effectively the flowering compared to GA₃ only. Also, flower-leaf ratio was significantly decreased by the application of GA₃3 25 (0.54) and 50 (0.41) mg?L -1 with machine oil emulsion mixture in comparison to GA₃ 25 (0.86) and 50 (0.60) mg?L -1 only. The number of leaves per fruit increased in application of GA₃ and machine oil emulsion mixture as concentration of GA₃ increased. Fruit weight and sugar-acid ratio also increased in comparison to the control whereas fruit size, soluble solid content and acidity remained unchanged. From the results, it was suggested that GA₃ application can reduce the number of flowers on the alternate bearing of satsuma mandarin. Moreover, application of GA₃ (25 and 50 mg?L -1 ) with machine oil emulsion 100 times mixture can reduce the flowering effectively without altering fruit maturity and soluble solid contents. Therefore, it can be concluded that the application of GA₃ 25 and 50 mg?L -1 with machine oil emulsion 100 times might be useful in controlling alternate bearing in satsuma mandarin.