長實金柑(Fortunella margarita Swingle) 果實發育及遮光與葉果比對其果實品質之影響

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Abstract Kumquat (Fortunella Swingle) is a small fruit-bearing tree in the genus Fortunella, family Rutaceae and subfamily Aurantoideae. Although kumquat was discovered for long time ago, related studies on kumquat are still limited. In order to investigate the biological characteristics of oval kumquat fruit from blooming to fruit ripe, and effects of the shading and fruit thinning on its quality, three dependently experiments were carried out at the Viticulture Research Station of National Chung Hsing University (NCHU), Wufeng, Taichung, Taiwan in 2006-2007. Three-years-old oval kumquat (Fortunella margarita Swingle) trees were used in these experiments. In the first experiment, fruits of six trees were harvested at different developmental stages 20, 30, 40, 50, 60, 70, 80, 90, 100 and 109 days after full bloom, and the fruit width, fruit length, fruit weight, fruit volume, component parts of fruit, total soluble solids (TSS) and titratable acid (TA) in juice and in whole fruit (fruit ripe) were measured. The developments of fruit and component parts in fruit were described by growth curves. The results showed that the fruit width and fruit length rapidly increased in early stage to 40 days and slowly increased to 100 days after full bloom, and then seem to no increase in 10 days before fruit ripe. Fruit weight and volume regularly increased from 20 to 100 days after full bloom then slightly increased until fruit ripe. An increase of TSS in juice was observed to about 10 days before fruit ripe, and then hardly increased during fruit ripe, whereas TA content of juice only increased in the early stage of fruit development until approximately 60 days after full bloom, and then decreased until fruit ripe. Simultaneously with the first experiment, two other experiments were carried out to test the effects of shading and leaf-to-fruit ratios on the quality of kumquat fruits. Sixteen oval kumquat trees with a tunnel form temporary nethouse were used to determine the effects of shading on fruit quality. Trees were covered with nets (50 % shading) from the 40th day after full bloom until fruit ripe. Results indicated that fruit size and fruit weight were higher (2.44 % in width, 1.85 % in height, 5.86 % in volume and 6.52 % in weight) in shaded treatments compared to control trees. TSS in fruit juice was decreased by shading, but there was not significantly different in TSS of peel and the ratio of TSS to acidity. The color of fruits was decreased by shading. For experiment 3, the effect of leaf-to-fruit ratios on kumquat fruits quality was tested. Twenty-four kumquat trees were selected and fruit thinning was conducted to provide 5, 10, 15 and 20 leaves per fruit of treatments. The results indicated that increasing the leaf-to-fruit ratio to 10 resulted in significantly 5.52 % heavier fruit and 0.38 oBrix higher compared to 5 leaves per fruit. Although increasing the leaf-to-fruit ratio to 15 resulted in significantly 4.19 % heavier fruit, there was not significantly different in TSS compared to 10 leaves per fruit. Increasing the leaf-to-fruit ratio to 20, there was not significantly difference in fruit weight and TSS compared to 15 leaves per fruit, but the fruit weight and TSS were significantly higher than the group of 10 leaves per fruit treatment (6.6 % and 0.22 oBrix, respectively). Increasing leaf-to-fruit ratio to 20 resulted in a darker red and yellow color of the fruit skin. It is clear that using fruit thinning with 15-20 leaves per fruit are feasible strategies to improve kumquat production.