시설재배 不知火의 수체생장과 과실품질에 미치는 대목 및 온도의 영향

Abstract

In order to develop the cultural practices for sustainable production and improvement of fruit quality of 'Shiranuhi' [(Citrus unshiu × C. sinensis) × C. reticulata] in plastic film house, several experiments on the effect of rootstock and temperature on the tree growth and fruit quality during the early growth stage and maturing stage, and on the composition of sugar and acid and related-enzyme activities were conducted from 2001 to 2005. The results of the experiments obtained are summarized as follows; 1. Effect of stock on tree growth and fruit quality. Two treatments were compared from October 2002 to January 2003 such as topworking of 'Shiranuhi'/'Miyagawa Wase' satsuma mandarin/trifoliate orange (interstock) and common grafting of 'Shiranuhi'/trifoliate orange (control) in three areas. And five rootstocks were compared in 2004 to 2005 namely, trifoliate orange (Poncirus trifoliata), 'Swingle' citrumelo (C. paradisi × P. trifoliata), shiikuwasha (C. depressa Hayata), yuzu (C. junos Sieb.), and natsudaidai (C. natsudaidai). 1.1. Fruit width, fruit weight, peel colour and flesh rate of 'Shiranuhi' were not different in two treatments. 1.2. The total soluble solid content in terms of juice Brix was also not different in two treatments. Titratable acidity in interstock increased significantly by 0.3% compared with the control throughout all growth stages. The sugar-acid ratio in interstock was 8.6 at maturing period, which was 2.4 lower than that in the control. 1.3. The free sugar showed increasing trend in both interstock and control and there was no significant difference between the two treatments. The concentration of sucrose tended to decrease while glucose and fructose generally increased in interstock. 1.4. The trunk diameter, spring shoot length, and the height, and width of the tree were significantly higher in 'Swingle' citrumelo and shiikuwasha than the other rootstocks in 2004 and 2005. 1.5. The fruit widths were not significantly different in five rootstocks. The fruit height of 'Swingle' citrumelo was the highest compared with other rootstocks, indicating a decrease in fruit shape index. The number of fruits and the yield per tree in 'Swingle' citrumelo were significantly highest among the rootstocks studied in 2004 and 2005. 1.6. The sugar content and titratable acidity in 'Swingle' citrumelo and shiikuwasha were significantly lower than those of trifoliate orange. 1.7. The concentration of total sugar and glucose in 'Swingle' citrumelo and shiikuwasha rootstock was lower than those of other rootstocks, but the concentration of sucrose in 'Swingle' citrumelo increased with 55% of total sugar, which was higher than other rootstocks. In 'Swingle' citrumelo, concentration of citric acid was lower and malic acid was higher than trifoliate orange. 1.8. The activity of sucrose synthase (SS) in trifoliate orange was higher than in the other cultivars. 2. Effect of air temperature on the tree growth and fruit quality. Three treatments were compared such as combinations of minimum night temperature of 15℃ and maximum day temperature of 25℃ (15-25℃), 18℃ and 28℃ (18-28℃), and ambient and 20℃ (control) during the early growth stage from February 20 to May 30, 2002. And three treatments were compared in 2003 to 2004 such as combinations of minimum night temperature of 5℃ and maximum day temperature of 15℃ (5-15℃), 10℃ and 20℃ (10-20℃), and ambient and 10℃ (control) during the maturing stage from December 2003 to January 2004, in cultivars 'Shiranuhi', 'Kiyomi' (C. unshiu × C. sinensis), and 'Tsunogaori' [(C. unshiu × C. sinensis) × C. unshiu Marc.)]. 2.1. The number of spring shoots decreased, the leaf area was broadened, and the length of spring shoot increased in all the cultivars tested as air temperature during the early growth stage increases. 2.2. The apparent photosynthetic rate in 'Shiranuhi' increased as air temperature during the early growth stage increases, showing that apparent photosynthetic rate in 18-28℃ was 16.7 μ㏖ CO₂?m^(-2). s^(-1), which was 1.5 times higher than that in the control. 2.3. The date of full bloom in the control was April 22, which was 24 days and 44 days later than that in 15-25℃ and 18-28℃ in 'Shiranuhi', respectively. The flower-leaf ratio had a decreasing trend as air temperature during the early growth stage increases in all cultivars. The increment of leaf-fruit ratio in 18-28℃ was caused by the reduction in number of flower inspite of the increased fruiting rate in 'Shiranuhi', which on the other hand, was caused by lower fruiting rate in 'Kiyomi' and 'Tsunogaori' 2.4. The fruit size in all cultivars increased as air temperature during the early growth stage increases. The fruit shape index in 'Shiranuhi' was especially lowered by increasing fruit height. 2.5. The increasing trend of sugar content in 'Shiranuhi' fruit during the maturing stage was similar in both control and 15-25℃, but slower in 18-28℃. The sugar content in fruits at harvest reduced due to the advanced harvest as air temperature during the early growth stage increases. 2.6. The titratable acidity in all cultivars decreased as air temperature during the early growth stage increases. 2.7. The results of this study suggest that the appropriate heating temperature during the early growth stage in 'Shiranuhi' was about 15℃ in the night. 2.8. The relative humidity in plastic film house tended to increase as air temperature during the maturing stage increases, indicating about 70% in control and 90% in 10-20℃. The relative humidity during the day in three treatments did not change, except for a decrease in 3?5 PM readings in all the treatments. 2.9. The sugar content was not affected by temperature during the maturing stage. However, the concentration and percentage of glucose and fructose to total sugar decreased, but those of sucrose increased as air temperature increases. 2.10. The titratable acidity and total organic acid had a decreasing tendency as air temperature during the maturing stage increases. The concentration of organic acid decreased significantly with high temperature, indicating that the concentration and percentage of citric acid to total organic acid decreased, but those of malic acid increased as air temperature during the maturing stage increases. 2.11. The rate of rotted fruit increased significantly, with decreasing Hunter b* value as air temperature during the maturing stage increases. 3. Changes in sugar and organic acid composition and activities of related enzymes during fruit maturation. Changes in the free sugar and organic acid composition and activities of related enzymes during fruit maturation in 'Shiranuhi' were compared with sour orange (C. aurantium L.), sucarri (C. sinensis L.) and 'Okitsu Wase' (C. unshiu Marc.) grown in plastic film house. 3.1. The juice Brix of 'Shiranuhi' fruit was the highest throughout all stages in four cultivars. The titratable acidity was highest in sour orange fruit and the lowest in succari. 3.2. The concentration of total sugar in 'Shiranuhi' was lower than that of sucarri, in spite of the highest juice Brix reading in 'Shiranuhi'. Moreover, sucarri fruit had the highest free sugar concentration, particularly the glucose and fructose concentration among the four cultivars evaluated and this tendency persisted throughout fruit maturation. The concentrations of sucrose in 'Shiranuhi' and 'Okitsu Wase' were high throughout all stages. 3.3. The concentration of total organic acid in 'Shiranuhi' fruit was in between the levels of succari and sour orange, but malic acid was higher than in sour orange in December. 3.4. The activities of sucrose synthase (SS) and sucrose-phosphate phosphatase (SPP) tended to increase as total sugar content increases and citric acid content decreases. SS activity in 'Shiranuhi' was higher than in 'Okitsu Wase' and sour orange, but was not different with succari. SPP activity in 'Shiranuhi' was similar to 'Okitsu Wase' and in between the levels of succari and sour orange.