Seasonal Variations in Fruit Characteristics and Relationships among Them in Keraji (Citrus keraji) Masashi YAMAMOTo1, Rumiko KouNo1, Keiko UENO1, Fumio HASHIMOTO1, Kenji KOBASHII, Ryoji MATSUMOTO2, Terutaka YOSHIoIc 3 and Shigeto TOMINAGAI1 1Faculty of Agriculture, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan 2Faculty of Agriculture, Saga University, Honjo-machi, Saga 840-8502, Japan 3Department of Citriculture Kuchinotsu, National Institute of Fruit Tree Science, Kuchinotsu, Nagasaki, 850-2501, Japan Abstract Seasonal variations in fruit characteristics and relationships among them in keraji (Citrus keraji), which is a local cultivar mainly grown on Kikai-jima island, Kagoshima prefecture were studied. Although the fruit of Keraji was inferior to that of satsuma mandarin (C.unshiu) in terms of coloration of skin, the titratable acidity of Keraji was almost the same as that of eokitsu wase f which is an early ripening clone of satsuma mandarin. The Brix value of Keraji which was slightly higher than that of eokitsu wase f, increased until early February. Sugars in the juice of Keraji consisted of fructose, glucose and sucrose. Sucrose was the predominant sugar component, followed by glucose and fructose in mature fruit, and this composition was similar to that of many citrus accessions. On the other hand, the juice of Keraji showed characteristic acid constituents. The content of citric acid in juice decreased rapidly during the growth period, while the content of malic acid increased gradually from October. Consequently, the malic acid content was approximately 40% of the citric acid content in January and February. The contents of polymethoxy flavones (PMFs) which are characteristic phytonutrients of citrus in the juice of Keraji was almost the same as those of Ponkan (C. reticulata), one of the species with the highest PMF contents. On the other hand, the PMF contents in the peel were lower than those of Ponkan and Shiikuwasha (C.depressa). A positive correlation was revealed between the number of leaves, diameter of the peduncle and rind texture, and fruit weight. Generally fruits with coarse rind and good coloration display a low and high Brix value, respectively. The fruit weight was negatively correlated with the titratable acidity, but not significantly with the Brix value. The correlation between the number of seeds per fruit and the fruit weight was not significant. Key words: Acid, Citrus, Phytonutrient, Polymethoxy flavone, Sugar
Fig. 1 Seasonal changes in fruit weight of Keraji and control cultivars in 2000. Keraji ( œ), Okitsu vase ( ), Juman unshiu ( ). Vertical Fig. 3 Seasonal changes in color index of Keraji and control cultivars in 2000. Keraji ( œ), Okitsu wase ( ), Juman unshiu ( ). Color bar indicates }SE. index, 0: completely green -10: completely colored. Vertical bar indicates }SE. Fig. 2 Seasonal changes in shape index of Keraji and control cultivars in 2000. Shape index (Fruit diameter ~100/fruit length): Keraji ( œ), Okitsu wase ( ), Juman unshiu ( ). Vertical Fig. 4 Seasonal changes in flesh percentage of Keraji and control cultivars in 2000. Keraji ( œ), Okitsu wase ( ), Juman unshiu ( ). Vertical bar indicates }SE. bar indicates }SE.
Fig. 5 Seasonal changes in Brix value of Keraji and control cultivars in 2000. Keraji ( œ), Okitsu wale ( ), Juman unshiu ( ). Vertical bar indicates }SE. Fig. 6 Seasonal changes in titratable acidity of Keraji and control cultivars in 2000. Keraji ( œ), Okitsu wase ( ), Juman unshiu ( ). Vertical bar indicates }SE. Table 1 Seasonal changes in fruit characteristics of Keraji and control cultivar in 2001-2002 *1 Fruit diameter ~100/fruit length. *2 0: completely green -10: completely colored.
Fig. 7 Seasonal changes in sugar contents of Keraji and control cultivar in two seasons. Fructose content of Keraji ( Ÿ), glucose content of Keraji ( ), sucrose content of Keraji ( œ), fructose content of Okitsu wase ( ž), glucose content of Okitsu wase ( ), sucrose content of Fig.8 Seasonal changes in organic acid contents of Keraji and control cultivar in two seasons. Citric content of Keraji ( œ), malic content of Keraji ( ), citric content of Okitsu wase ( ), malic content of Okitsu wase ( ). Vertica l bar indicates }SE. Okitsu wase ( ). Vertical bar indicates }SE.
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