Search

The muscat flavor of table grapes often decreases after harvest, but the contributions of post-harvest temperature to the flavor loss were unknown. In the present study, the effect of different postharvest temperatures on muscat flavor and the content of aroma volatiles was investigated at 0, 2, 5, and 10 °C for 12 weeks in the berries of ‘Shine Muscat’ ( Vitis labruscana Baily × Vitis vinifera Vitis vinifera L.), which has a strong muscat flavor. Furthermore, after 2, 4, and 8 weeks of storage at 0 °C, the grapes were subjected to post-storage conditioning at 10 °C for 14 more days, and changes in the aroma volatile content were investigated. A sensory test showed that after 4 weeks of storage, the muscat flavor obviously decreased at 0 °C, but at 10 °C, the muscat flavor was maintained. Gas chromatography analysis of aroma volatiles showed that the content of linalool, which is one of the causative agents of muscat flavor, dramatically decreased at low temperatures (0, 2, and 5 °C) in comparison with that at 10 °C. During storage, the linalool content was much lower at 0 °C than at 10 °C in both the skin and the flesh. Interestingly, the linalool content, as well as muscat flavor, which decreased during storage at 0 °C, increased after the grapes were subjected to post-storage conditioning at 10 °C. The linalool content of the grape conditioned at 10 °C for 1–14 more days was higher than that of the grape continuously stored at 0 °C. These results indicated that muscat flavor is strongly influenced by postharvest temperature and that low-temperature storage enhances the loss of muscat flavor and the decrease in linalool content, but storage at 10 °C delayed and minimized them. Moreover, these results showed that post-storage conditioning at an increased temperature before consumption would be effective to increase the muscat flavor even after flavor loss during low-temperature storage at 0 °C.

The effects of ethylene and red light-emitting diode (LED) light (660 nm) on the accumulation of carotenoid and expression of genes related to carotenoid biosynthesis were investigated in the flavedo of Satsuma mandarin. The results showed that the contents of β-cryptoxanthin, all- trans -violaxanthin, 9- cis -violaxanthin and lutein were simultaneously increased along with the total carotenoid accumulation by the red LED light. With the ethylene treatment, the contents of β-carotene and β-cryptoxanthin were increased, while the content of lutein was decreased in the flavedo. The suppression of lutein accumulation by ethylene was inhibited when the ethylene treatment was performed under the red LED light. With the combination of ethylene and red LED light treatments, the contents of β-cryptoxanthin and lutein were simultaneously increased. Gene expression results showed that simultaneous increases in the expression of CitPSY , CitPDS , CitZDS , CitCRTISO , CitLCYb1 , CitLCYb2 , CitLCYe , CitHYb , and CitZEP contributed to the accumulation of β-cryptoxanthin and lutein in the treatment of ethylene combined with red LED light. The results presented might provide new strategies to enhance the commercial and nutritional value of citrus fruit.

We developed 708 gene-based markers for citrus genome analysis. Sequence-tagged site (STS) primers were designed that were located in conserved exon regions and whose PCR products spanned genomic introns. Of these, 79.7 % comprised cleaved amplified polymorphic sequence markers. The gene-based markers and their annotation and position on Clementine scaffolds ver. 1.0 permitted comparison of the genetic map and the Clementine genome sequence. The 708 gene-based markers were used to construct a genetic map using the 87 progenies (AG population) from the cross between ‘Okitsu 46 gou’ (‘Sweet Spring’ (‘Ueda unshiu’ (Citrus unshiu) × Hassaku (Citrus hassaku Hort. ex Tanaka)) × ‘Trovita’ orange) × ‘Kankitsu Chukanbohon Nou 5 gou’ (‘Lee’ (Citrus clementina × tangelo) × Citrus kinokuni). The markers were integrated using common STSs on different phase maps in cross-pollination mode. The integrated map (AGI map) comprised 706 loci, including two morphological traits, and spanned 990.9 centimorgans (cM) with an average marker distance of 1.40 cM. These markers formed nine linkage groups (LGs) (corresponding to citrus physical chromosomes): LG-01 to LG-09 corresponded to Scaffold_01, Scaffold_07, Scaffold_09, Scaffold_06, Scaffold_03, Scaffold_02, Scaffold_04, Scaffold_08, and Scaffold_05, respectively. LG-08 and LG-09 contained morphological traits controlling embryo color and seedlessness. Eighty-eight loci comprised three or more alleles on the AGI map; 36.4 % of them were related to transcription factors and DNA-binding proteins. The 708 gene-based markers and the AGI map are valuable for integrating various citrus genetic maps, alignment of genomic sequences, chromosome assignment, and understanding the diversity of citrus germplasms.

To learn how to regulate carotenoid content in citrus fruit, we studied the mechanism of carotenoid accumulation using physiological and genetic methods. Based on differences in the carotenoid profiles of flavedo and juice sacs, citrus species could be roughly divided into three groups: carotenoidpoor, violaxanthin-abundant, and b-cryptoxanthin-abundant groups. A comparison of the gene expression among several citrus species with different carotenoid profiles showed that the difference in carotenoid profiles among citrus species was highly regulated by coordination of the expression for genes related to carotenoid biosynthesis and catabolism. Quantitative trait loci related to carotenoid content were also identified to select progeny with high carotenoid content. Moreover, we showed that the effect of postharvest ethylene on carotenoid accumulation in flavedo varied with temperature. Under an ethylene atmosphere, in flavedo, carotenoid accumulation was enhanced more dramatically than under an ethylene-free atmosphere at 20°C but repressed at 5°C.

The effects of electrostatic atomization on ascorbate (AsA) metabolism in broccoli (Brassica oleracea L. var. italica) were studied and the possible molecular mechanisms discussed. Electrostatic atomization, delayed the yellowing process, and ethylene production and respiration rates were significantly suppressed in broccoli after harvest. The AsA content declined rapidly to a lower level in the controls after harvest, and the reduction of AsA was suppressed by the treatment with electrostatic atomization during the storage period. In addition, modulation of the AsA reduction by electrostatic atomization was highly regulated at the transcription level. Up-regulation of the AsA biosynthetic genes (BO-VTC1, BO-VTC2, and BO-GLDH), and AsA regeneration genes (BO-MDAR1, BO-MDAR2, and BO-DHAR) led to the suppression of AsA reduction in broccoli treated with electrostatic atomization after harvest. These results indicated that electrostatic atomization treatment might be a new effective approach for delaying the senescence of broccoli.

We developed a 384 multiplexed SNP array, named CitSGA-1, for the genotyping of Citrus cultivars, and evaluated the performance and reliability of the genotyping. SNPs were surveyed by direct sequence comparison of the sequence tagged site (STS) fragment amplified from genomic DNA of cultivars representing the genetic diversity of citrus breeding in Japan. Among 1497 SNPs candidates, 384 SNPs for a high-throughput genotyping array were selected based on physical parameters of Illumina’s bead array criteria. The assay using CitSGA-1 was applied to a hybrid population of 88 progeny and 103 citrus accessions for breeding in Japan, which resulted in 73,726 SNP calls. A total of 351 SNPs (91 %) could call different genotypes among the DNA samples, resulting in a success rate for the assay comparable to previously reported rates for other plant species. To confirm the reliability of SNP genotype calls, parentage analysis was applied, and it indicated that the number of reliable SNPs and corresponding STSs were 276 and 213, respectively. The multiplexed SNP genotyping array reported here will be useful for the efficient construction of linkage map, for the detection of markers for marker-assisted breeding, and for the identification of cultivars.

To aid the breeding of citrus (Citrus sp.) for high carotenoid content, we assayed the fruit flesh of 48 cultivars and selections within a parental population consisting of both old and new cultivars and selections at two locations in Japan. The mean total carotenoid (CAR) content across all 48 cultivars and selections over the two locations was 26.59 μg·g−1 fresh weight (FW). The most prominent carotenoid was β-cryptoxanthin [BCR (12.09 μg·g−1 FW)] followed by violaxanthin [VIO (8.04 μg·g−1 FW)], ζ-carotene (2.27 μg·g−1 FW), phytoene (1.86 μg·g−1 FW), and β-carotene (0.96 μg·g−1 FW). Broad-sense heritabilities of CAR, BCR, and VIO were 0.80 or greater based on a sample of five fruit on one tree per location in one time sampling for 1 year in a location, which were revealed to be large enough for gauging the genetic variation. The mean CAR and BCR contents in a cultivar and selection group in advanced generations were nearly the same as in the initial population, suggesting no or little selection pressure on carotenoid content in the citrus breeding so far. High carotenoid contents in cultivars and selections released or selected recently, which have high fruit qualities, suggest their high potential for combining high fruit quality and high carotenoid content in breeding. We showed that the critical phenotypic value used in selecting hybrid seedlings can be determined from the estimate of environmental variance.

The effects of 1-methylcyclopropene (1-MCP) on ascorbate (AsA) metabolism in two cultivars of broccoli ( Brassica oleracea L . var. italica ), ‘Haitsu’ and ‘Ryokurei’, were studied and the possible molecular mechanisms are discussed. The results showed that 1-MCP treatment delayed the yellowing and suppressed ethylene production. Meanwhile, the AsA content declined to a lower level in the control during storage, and the reduction of AsA was significantly suppressed by the treatment with 1-MCP in the two cultivars. Gene expression analyses by real-time PCR showed that 1-MCP treatment down-regulated the expression of BO-APX1 and BO-APX2 , and up-regulated that of BO-DHAR and BO-GLDH compared with the control. The regulation of this gene expression might contribute to the suppression of AsA reduction by the 1-MCP treatment in ‘Haitsu’ and ‘Ryokurei’ broccoli. The results arising from this study might provide new insights into the possible mechanism, by which treatment with 1-MCP delayed senescence.

Gibberellin 3 (GA 3 )-responsive genes were investigated with a citrus 22K oligoarray 1 to further the understanding of transcriptional regulation by GA 3 treatment in Satsuma mandarin fruit ( Citrus unshiu Marc.). 213 GA 3 -responsive genes were identified that showed a 3-fold or greater expression change after 72 h GA 3 treatment, compared to expression after 72 h air treatment. GA 3 treatment induced expression of pathogenesis-related (PR) proteins and genes that function in photosynthesis, chloroplast biogenesis, resistance, defense and stress. Also, GA 3 treatment reduced the transcription of several ethylene-inducible genes, such as carotenoid metabolic genes, which are associated with fruit ripening. Contrasting effects between GA 3 and ethylene were observed on photosynthesis and chloroplast biogenesis, chlorophyll metabolism, and carotenoid metabolism, indicating that the endogenous GA 3 level might be important for the endogenous regulation of maturation and senescence in mature citrus fruit. It was also found that the GA response pathway was likely to take part in cross-talk with the pathogen-related pathway in mature citrus fruit.

The relationship between sugars and ethylene was investigated in harvested broccoli ( Brassica oleracea L. var. italica ) florets. Broccoli florets senesced rapidly after harvest at ambient temperatures, accompanied by the yellowing of sepals, ethylene production and degradation of sugars. In harvested broccoli, continuous uptake of a 10% sucrose (Suc) solution through the cut surface of the stem enhanced ethylene production in florets with simultaneous increases in 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) activity and ACC content. In spite of the increased rate of ethylene production, the yellowing of sepals and the expression of ACC oxidase (ACO) gene were suppressed by the Suc feeding. When florets were immersed in a 50 mM glucose (Glc) or Suc solution for 24 h, ethylene production was increased by both treatments, and ACS activity and ACC content were the highest in Glc-treated samples. The expression of the ACO gene was enhanced in florets exposed to ethylene (82 μl l −1 ). However, the increases in ethylene production and ACO mRNA accumulation observed in the samples treated with ethylene were suppressed when broccoli plants were treated with ethylene and Suc together. These results indicate that Suc and Glc can affect the rate of ethylene biosynthesis and that high levels of sugars decrease ethylene sensitivity in harvested broccoli florets.

Two distinct clones having high nucleotide identity to the sequences encoding ascorbate peroxidase (APX) were isolated from broccoli (Brassica oleracea L. var. italica). Deduced amino acid sequences of both cDNAs, BO-APX 1 (accession number AB078599) and BO-APX 2 (accession number AB078600), shared identity of 92.8% and there was more than 80% identity between BO-APXs and other plant cytosolic APXs at the protein level. Gene expression and protein levels of BO-APX 1 and BO-APX 2 were investigated in various parts of broccoli after harvest. Transcript levels of BO-APX 2 gradually increased in florets, while those of BO-APX 1 decreased in florets after harvest. BO-APX 1 and BO-APX 2 were expressed in Escherichiacoli as a fusion protein with glutathione S-transferase (GST) and purified to homogeneity by glutathione sepharose 4B column chromatography. Both proteins of BO-APX 1 and BO-APX 2 appeared as a single major band on SDS-PAGE corresponding to a mass of 25 kDa and reacted with polyclonal antibodies raised against recombinant BO-APX 1. Both enzymes showed high specificities for ascorbate and hydrogen peroxide. The km values of recombinant BO-APX1 and BO-APX 2 for ascorbate were 395 and 526 μM and those for hydrogen peroxide were 15 and 7 μM, respectively. The role of APX was discussed in relation to ascorbate breakdown in broccoli florets during senescence.

Broccoli ( Brassica oleracea , var. italica ) florets (flower buds) senesced rapidly after harvest at ambient temperatures. ACC (1-aminocyclopropane-1-carboxylic acid) synthase (ACS) was induced rapidly in the cut surface of stem tissue in the first 2 mm thick and the basal portions of curds soon after harvest, leading to an accumulation of ACC. The abundance of one ACS mRNA (BO-ACS1) increased in the first layer, the inner layer of stem (2–4 mm, second layer), and the basal portion of curds, while the transcripts for another (BO-ACS2) increased only in the first layer. Conjugated ACC (malonyl ACC, MACC) levels increased in all portions as senescence progressed. In florets, ACC synthase activity and BO-ACS1 transcripts were detected with no significant changes observed during senescence. ACC levels in florets stayed low throughout the experimental period, whereas MACC levels were much higher than those of ACC. The marked rise in ACC oxidase (ACO) activity in florets was detected almost in parallel with a significant increase in ethylene production. The abundance of ACO transcripts (BO-ACO1 and BO-ACO2) increased concurrently with the rise in ACC oxidase activity. These findings suggest that ACC and ethylene synthesized in the stem in response to wounding may have involved the enhanced activity of ACC oxidase and increased abundance of its transcripts in florets.

Dihydrochalcone derivative, 3',5'-di-C-beta-glucopyranosylphloretin (1), is present in the genus Fortunella, (F. crassifolia, F. japonica, F. margarita, F. polyandra and F. hindsii). These species accumulate a large quantity of 1 in their fruits (peel, 6.5-15.2 mg/g in dry wt; juice sac, 1.5-10.5 mg/g) and in their leaves (21.3-60.2 mg/g). Twenty-seven Tanaka's Citrus species examined lack 1, but C. madurensis and C. halimii contain 1 in large quantities in their peels (25.1 and 33.6 mg/g) and juice sacs (4.1 and 4.2 mg/g). Poncirus species do not contain 1. Fortunella-citrus hybrids, the Orangequat [C. unshiuxF. crassifolia], the Thomasville citrangequat [Fortunella sp.x(C. sinensisxPoncirus trifoliata)], and seven hybrid progenies [F. margaritaxC. junos], contain large amounts of 1 in their peels (17.0-7.9 mg/g) and juice sacs (2.0-9.9 mg/g). These facts suggest that accumulation of 1 is a generic trait of the genus Fortunella and that the inheritance of the trait among the intergeneric hybrids is controlled by a dominant allele. Thus C. madurensis and C. halimii are thought to originate from natural hybrids between the genera Citrus and Fortunella. Phloridzin, which has the same aglycon as 1, was not detected in the citrus plants examined.

Broccoli (Brassica oleracea L. var. italica) florets senesced rapidly after harvest at ambient room temperatures. Whole plants of broccoli were harvested in the field and brought to the laboratory, then the stem was excised from the root. Ethylene production in the first cross-sectional layer (2 mm thick) initially increased markedly from a trace amount at 0 hr to a peak at 12 hr, then decreased gradually. The rate of ethylene production in florets increased gradually after harvest to reach a maximum at 24 hr. A high amount of ascorbate in florets at harvest, just after separation from the stem, rapidly declined to a low level during senescence. However, in the stem tissue including the cut surface, the ascorbate level which was much less than that of florets, remained almost unchanged during the experimental period. Ascorbate peroxidase (APX), which may be responsible for the first step in ascorbate oxidation retained high activity in broccoli florets after harvest, then decreased slightly during senescence. These results suggest that some additional factors (components) besides high APX activity could be involved in the rapid breakdown of ascorbate.

The rate of ethylene production in sweet potato ( Ipomoea batatas Lam) root tissue greatly increased in response to infection by black rot fungus ( Ceratocystis fimbriata Ell. & Halst.). Ethylene evolved rapidly in the first layer of root cells (0–0.5 mm) 24 h after inoculation with the endoconidia of the fungus. In this layer, the host-parasite interactions were very strong. Ethylene production rate reached a peak (up to 300 nl g −1 h −1 ) 24 h after inoculation, and then declined to a low level. This was followed by an increase in ethylene production in the second layer of cells (0.5–1.0 mm) following continuing invasion by the fungus. Incorporation of l -[ 14 C(U)]methionine into ethylene 24 h after inoculation occurred at a lower rate in the first cell layer than in the second, where the ethylene production rate was about 15-fold less. When ACC (1-aminocyclopropane-1-carboxylic acid) was supplied externally, the rate of ethylene production in the first layer was not enhanced, and neither was [ 14 C]methionine incorporation into ethylene diluted. The activity of ACC oxidase extracted from the first layer was extremely low (less than 10 nl g −1 h −1 ) when compared with the ethylene production rate, although ACC oxidase protein was weakly detected by Western blot analysis in the extract from the infected tissue using antibodies raised against ACC oxidase purified from recombinant Escherichia coli . These results indicate that the predominant ethylene generated in the site adjacent to the invaded region of sweet potato root tissue may originate from a pathway independent of ACC. However, it is possible that the methionine-ACC pathway may operate in tissue internal to the above active site.

To use recombinant 1-aminocyclopropane-1-carboxylate (ACC) oxidase for research on ethylene biosynthesis, the biochemistry of both recombinant and endogenous ACC oxidase from kiwifruit was compared. When induced by the addition of isopropyl-β- d -thiogalactopyranoside (IPTG) to Escherichia coli (E. coli) cells transformed with cDNA AD-ACO1 using the pGEX-4T-1 vector, ACC oxidase identical to that from kiwifruit was expressed as a polypeptide of 37 kDa. Apparent Km values for ACC for both recombinant and endogenous ACC oxidase were 41 and 16 μM, respectively. Both forms of ACC oxidase exhibited absolute requirements for ferrous iron, ascorbate and bicarbonate for maximum activity The activities of both enzymes were inhibited by ethylenediaminetetraacetic acid (EDTA), 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron), o-phenanthroline (PA), α-aminoisobutyric acid (AIB), and p-chloromercuriphenylsulfonic acid (PCMPS). Addition of dithiothreitol (DTT) stimulated activity of both ACC oxidases. The results indicate that the recombinant ACC oxidase was similar biochemically to the endogenous kiwifruit enzyme. Western blot analysis using antibody raised against purified transformed ACC oxidase protein showed differential expression of endogenous ACC oxidase protein in kiwifruit during ripening. Expression may start in the columella region and then increase in surrounding tissues with progressive stages of ripening.

Parthenocarpic kiwifruit Actinidia deliciosa was produced and induction of ethylene synthesis in response to ethylene treatment studied. At anthesis, flowers were treated with N -(2-chloro-4-pyridyl)- N ′-phenylurea (CPPU). CPPU-treated parthenocarpic fruit and pollinated normal fruit were harvested in early November, and then treated with 1000 μ l l −1 ethylene at 20°C for 24 h. Ethylene production following ethylene treatment was reduced and delayed in the parthenocarpic fruit. To investigate the mechanism of this reduction in ethylene synthesis, 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations, and gene expression of ACC synthase (using a cDNA probe, AD-ACS1) and of ACC oxidase (with a cDNA probe, AD-ACO1) were analyzed. ACC concentrations and levels in ACC synthase transcripts increased in the pollinated fruit 2 days after the 24 h ethylene treatment, but not in the parthenocarpic fruit. Accumulation of ACC oxidase transcripts was stimulated immediately by the 24 h ethylene treatment in both pollinated and parthenocarpic fruit. These results suggest that suppression of ethylene synthesis in parthenocarpic fruit resulted mainly from suppressed expression of ACC synthase.

Large varietal differences in ethylene production in Chinese kiwifruits were found, especially between 'Kui mi' and 'Hong xin', based on the sensitivity and responsiveness of the cultivars to exogenous ethylene, which could induce autocatalytic ethylene production in fruit. The difference in the potential to induce ethylene production is attributed to the greater gene expression of ACC synthase in 'Kui mi' than in 'Hong xin'. In contrast, no distinct differences were found in the transcript levels of ACC oxidase gene between these cultivars. 'Kui mi' having a high rate of ethylene production also had a high ACC content compared with 'Hong xin'. When endogenous ethylene production reached a peak at 96 hr after 24 hr-ethylene treatment, the transcript levels of ACC synthase gene were most prominent. However, the transcript level of ACC oxidase gene was clearly detected in all samples of 0 hr and more after a 24 hr-ethylene treatment. These results suggest that a key enzyme which controls the rate of endogenous ethylene production in kiwifruit is ACC synthase, not ACC oxidase.

Methods for extracting total RNA from various tissues of satsuma mandarin and kiwifruit were examined. Satisfactory yields in total RNA were obtained from tissues with the exception of the albedo tissue of satsuma mandarin, by using a modification of the conventional extraction method devised for fruit tissues by Lopez-Gomez and Gomez-Lim (1992). In the albedo tissue, the polysaccharides may interfere with RNA extraction but further modification of the extraction method improved its yield. The modification involved repeated back extraction, chloroform/isoamyl alcohol extraction, and increasing the volume of the aqueous phase before precipitating RNA with LiCl (3 M final concentration). From the total RNA, poly (A)+RNA was purified using an oligo (dT) -cellulose column. The poly (A)+RNA could be successfully used for Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and the construction of a cDNA library. This modified protocol is applicable to other fruit tissues rich in polysaccharides.

Ethylene is involved in the premature senescence of broccoli after harvest. In an effort to understand the regulation of ethylene responses, we isolated three partial cDNAs from broccoli, BO-ETR1, BO-ERS, and BO-ETR2 as putative ethylene receptors. BO-ETR2 is a novel cDNA and it shared 77%, 68%, and 58% nucleotide identities with Arabidopsis ETR2 and tomato LeETR4, and BO-ETR1, respectively, in the corresponding regions of 479 bp long. Northern-blot analysis revealed that BO-ETR1 and BO-ERS mRNA were expressed in all examined parts of stem tissue and florets, but the transcription levels were higher in the stem tissue than in florets. During the broccoli senescence no significant change occurred in the expression of BO-ETR1 gene in either the stem or floret tissue. BO-ERS transcripts increased during the first 12 hr after harvest in the first layer of stem cutting, but decreased in the basal portion of curds. BO-ETR2 mRNA, which was maximum at harvest (0 hr), was detected only in the stem tissue. A significant reduction of BO-ETR2 transcripts was observed 36 hr after harvest. The results indicate that the gene expression for the above putative ethylene receptors in broccoli is regulated in a tissue specific manner.

Seasonal changes in the physical properties and chemical constituents of fruits during the maturing stage were examined in 5 strains of very early ripening mutants of Satsuma mandarin (Citrus unshiu Marc. var praecox Tanaka) with special reference to the limonoid compounds.The fruit size showed no significance during harvests performed 5 times successively. The proportion of peel of 'Hashimoto wase' was higher than other strains and peel-puffing was occurred. The Brix value increased in almost all the strains during fruit maturation and the sucrose contents mainly increased among the sugar constituents. Organic acid contents decreased, in particular citric acid as in the case of Wase satsuma mandarin. Both contents of limonin and nomilin were reduced with fruit maturation, but the rate of decrease of nomilin was faster than that of limonin. In the fruits harvested late, juice processing was optimal in terms of chemical components except for 'Hashimoto wase'.Since the correlation coefficients between the Brix value, citric acid or rind color a-value and limonoid compounds were very high, bitterness due to the presence of limonoids in the juice products could be predicted from several parameters. Based on the principal component analysis of the juice characteristics, 'Hashimoto wase' displayed different properties compared with the other strains. Based on this statistical method, it may become possible to develop a new classification of very early ripening mutants of Satsuma mandarin.

The physical and chemical properties of fruits used as raw materials for juice processing were examined among 12 strains in 6 classes of very early ripening mutants of Wase satsuma mandarin (Citrus unshiu Marc. var. praecox Tanaka) with special reference to the limonoid compounds.All the strains used in these experiments completely fulfilled the criteria of the Japanese Agricultural Standard (JAS) for single-strength juice. On the basis of these criteria, the sugar, citric acid, ascorbic acid (vitamin C), amino-nitrogen and ash contents in the very early ripening mutants were suitable for juice processing.However, the contents of limonoid compounds of these strains were much higher than those of Wase and Common satsuma mandarin at the usual harvest time. Such high contents may cause the so called "delayed bitterness" in their juice products after processing with an In-Line juice extractor. Therefore, to alleviate this shortcoming, it is suggested that the fruits should be harvested at the full ripening stage.Although the mutants were classified into 6 maturation types based on the variations of acid contents and coloring time of the fruit, the maturation time could not be estimated on the basis of the contents of limonoid compounds.

Large differences in gene expression of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, ACC contents, and ACC synthase activitiy were found in different tissues of fruit between members of two kiwifruit species, (cv) Actinidia chinensis ('Kui mi') and A. deliciosa ('Hayward'). ACC synthase mRNA accumulated mostly in the outer pericarp, slightly in the inner pericarp, and in a trace quantity in the columella of 'Hayward' fruit that produces much less ethylene than does 'Kui mi'. However, gene transcripts at significant levels exist in all sections of 'Kui mi' fruit which reflects a large potential to produce ethylene. ACC levels and ACC synthase activities were much higher in all the tissues of 'Kui mi' fruit than in 'Hayward' fruit, which indicates that these enzymes are the primary cause for the varietal difference in the ability to produce ethylene in kiwifruit.

The effects of ringing with or without hand defoliation on vegetative growth, flower bud differentiation, and physiological changes in young, container-grown satsuma mandarin (cv.Okitsu Wase) on trifoliate orange were investigated. Comparisons were made between trees grown under different temperatures in a growth chamber and those grown in the field. A ring of bark, 3 mm wide was removed 5 cm above the bud union. The wound was wrapped with a vinyl tape to prevent drying and to enhance callus development.1. Ringing in mid-June, after the spring growth flush ceased root growth within several days. After the ringing wound healed, new roots developed but the onset of the summer flush was delayed and shoot growth was depressed. Ringing in early September, after the summer flush stopped, not only depressed root growth, but it also prevented the initiation of new roots even though the girdles callused over. The absence of new roots is attributed to the lower air temperature in autumn. The autumn flush of new growth did not occur on treated trees.2. Potted trees were ringed in either mid-June, late July, or mid-September. Ringed and non-ringed trees were defoliated, and then transferred to a 25°C growth chamber at intervals of 1.5 months. Number of flowers and vegetative shoots which emerged after defoliation was observed. Defoliation in mid-June of non-ringed control trees required new growth over 10 days. When trees were defoliated in late July, bud break occurred within several days.However, trees required more days again in mid-September, and the maximum of 20 days in late October for bud break after defoliation. Trees ringed in mid-June and defoliated in late July, mid-September, or late October required 15, 9, and 17 days, respectively, to initiate regrowth. Ringed trees in July or September caused regrowth similar to that of non-ringed trees. Trees defoliated in early December, girdled in July or September, and held at 25°C produced many flowers, whereas those ringed in June produced few flowers.3. Trees, ringed on 1 September, and non-ringed trees were held at 15°, 20°, and 25°C in growth chambers or planted in the open field. The girdle produced more callus and healed faster at 25°C than at 20°C; no callus formed at 15°C. When trees at 25°C were defoliated in early December and kept at the same temperatures, bud break was delayed compared to those which were transferred to lower temperatures. Non-ringed trees held at 25°C produced few flowers, whereas ringed trees bloomed profusely. With or without girdles, trees kept at 15° and 20°C produced many flower buds; girdled trees kept at all temperatures had more flowers per sprouting node than did non-girdled ones.4. Analysis of leaves from non-girdled trees growing in the field and from those girdled on 1 September revealed that the sugar content in all samples increased in autumn. The in-crease is attributed to the low air temperatures. After ringing, leaf starch content increased to over 20% (dry weight basis) and then decreased. Nitrogen content decreased linearly until the wound callused over and then the level increased. The C/N ratio increased until the wound healed and then decreased. Transpiration resistance of the leaves was temporarily greater on ringed trees; the upward movement of the transpiration stream was, therefore, slower until the girdle healed.

ACC (1-aminocyclopropane-1-carboxylate) synthase cDNA (AD-ACS1), isolated from kiwifruit 'Hayward', was expressed as a fusion protein coupled with glutathione S-transferase (GST) in Escherichia coli. The fusion protein exhibited ACC synthase activity. Northern blot analyses showed that the transcripts hybridized with AD-ACS1 accumulated only in the outer pericarp after a 24-hr ethylene treatment.

国内の主要産地(26ヵ所)から取り寄せたキウイフルーツについて,追熟のためのエチレン処理に対する感受性を比較した.1) キウイフルーツを出荷用容器に入れ,エチレン発生剤(白石カルシウム製)を用い,15℃で追熟したところ,容器内のエチレン濃度は10～20μl・l-1,酸素16～18%,二酸化炭素3%程度となり,通常のキウイフルーツを追熟させるのに可能な条件となった.2) 果実硬度の低下によって判定した追熟の遅速には著しい産地間差があり,全体の69% (18産地)の試料はエチレン処理で速やかに追熟したのに対し,残り(8産地)は追熟が著しく遅れ,一部は最終的にも追熟しなかった.3) 追熟のしにくい産地の試料についてエチレン発生剤の量や処理温度を変えた条件でも追熟の促進が起こらず,産地間差には再現性が認められた.

The relationship between sucrose (Suc) and ascorbate (AA) metabolism was investigated in harvested broccoli (Brassica oleracea L. var. italica) florets. Decreases in both Suc and AA content were observed in broccoli florets 48 h after all the leaves were excised, but none were observed when the plants were kept intact or with leaves attached in a room at 20 degrees C. In harvested broccoli plants without leaves and roots, continuous absorption of a 10% (w/v) Suc solution from the cut surface of the stem suppressed the degreening of sepals and the loss of AA content in florets. The expression of the genes related to AA metabolism in chloroplasts and its biosynthesis were up-regulated by Suc feeding in broccoli florets. These data suggest that a decline in Suc leads to considerable damage not only to AA biosynthesis but also to the hydrogen peroxide-scavenging system in chloroplasts. In addition, the cessation of the Suc supply from leaves can be the main factor of AA degradation in harvested broccoli florets.

One-year-old satsuma mandarin (Citrus unshiu Marc. cv. Okitsu Wase) trees budded onto trifoliate orange rootstocks were subjected to different soil temperature (15, 20, 25 and 30°C) and air temperature treatments (25°C in Experiment I, and 15 and 30°C in Experiment II) for 6 or 7 months. The effects of air and soil temperatures on vegetative growth and flower bud differentiation were investigated.The number of flushes and total length of the shoots increased with rising soil temperatures. When soil temperatures were above 20°C, the number of flushes at an air temperature of 15°C was less than at 30°C. The length of spring shoots at an air temperature of 15°C was longer than at 30°C. However, due to the trees at air temperature of 30°C having more growth cycle flushes, the total length of the shoots did not differ among treatments. The dry weight of the trees increased with increases in both air and soil temperatures. Both low air and low soil temperatures affected flower induction greatly. At an air temperature of 30°C, flower buds developed only at soil temperatures of 15 and 30°C. At an air temperature of 15°C, flower buds developed even when the soil, temperature was 30°C. Trees with air/soil temperatures of 25/30, 30/25 and 30/30°C did not bear any flower buds. The effects of temperature on mineral nutrient content were slight. The roles of soil and air temperature on vegetative growth and flower formation are briefly discussed.

KODA [9-hydroxy-10-oxo-12(Z), 15(Z)-octadecadienoic acid] has previously been isolated from Lemna paucicostata, and is a compound known to promote flowering in plants. In this study, the effect of KODA on flower production and spring shoot occurrence in mature satsuma mandarin (Citrus unshiu Marc.) trees was examined in the field. The application of KODA in the summer or autumn had no discernible effect on flower production in the following year. However, when applied in summer, it promoted spring shoot occurrence in the following year, regardless of the number of flowers produced. In addition, C-KODA, a KODA analog, was more effective at producing this effect than KODA. The results suggest that the application of KODA or C-KODA may regulate spring shoot occurrence to improve the imbalance between the number of flower-bearing and vegetative shoots that leads to alternate bearing in satsuma mandarin trees.

To obtain genetic information on carotenoid content in Citrus fruit for a breeding program, we investigated quantitative trait loci (QTL) in a mapping population derived from a cross between ‘Okitsu-46’ and ‘Nou-5’. Among individual progeny, total and each carotenoid contents were segregated in a transgressive manner. QTLs for total and each carotenoid contents were detected by Kruskal-Wallis analysis (P 2.0) from 51 individuals. Most of the QTLs for each carotenoid component were mapped to different locations on the linkage map. In β-cryptoxanthin, the strongest QTL (LOD 3.4) was detected on linkage group 6 of ‘Nou-5’, and accounted for 26.9% of explainable variance. LOD scores of QTLs for total carotenoid content were lower than those for each carotenoid content. There were one QTL for total carotenoid content at the criteria of LOD > 2.0, and seven weaker QTLs, which overlapped with QTLs for each carotenoid component. The effects of QTLs detected for each carotenoid content worked cumulatively to increase total carotenoid content. This study provides preliminary data because we obtained data in only one season and from a limited number of individuals (n = 51). However, the results suggested that QTL information could be used to generate DNA markers to select progeny with higher carotenoid content.