The fruit thinning effect of Jasmonic acid derivative, n-propyl dihydrojasmonate (PDJ) on Japanese pear ‘Hosui’ was investigated. During the 1996 season, PDJ at 500, 1000, or 2000 ppm was applied to flower clusters at 17 or 12 days before full bloom (DBFB), at full bloom (FB), or at 7 days after full bloom (DAFB). During the 1998 season, PDJ at 500 or 750 ppm was applied to the whole tree at 18 or 14 DBFB. All PDJ treatments before full bloom induced fruit abscission and resulted in a thinning effect. The best results were obtained with 500 to 750 ppm PDJ applied at 17 or 18 DBFB. In these treatments, the proportion of clusters that had two or fewer fruits was about 64%, compared to the control which was 16%. In addition, the position of dropped fruit on the inflorescence axis in a cluster differed among treatments. In PDJ treatment, from the 1st to 3rd fruits from the base of the floral axis in the cluster tended to abscise easily. Abscission of the 1st and 2nd basal fruits was observed in about 90% of the clusters. There were no significant differences in fruit weight, flesh firmness, brix, and titratable acidity at harvest. PDJ did not inhibit pollen tube growth in the style of the pistil, but in flowers treated with PDJ there were many abnormal ovules at FB. These findings indicate that an application of PDJ at 500 or 750 ppm, 17–18 DBFB budbreak has a consistently good thinning effect. Histological examinations revealed that PDJ causes fruit thinning by preventing fertilization and/or causing seed abortion.

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Whether or not powdery mildew resistant and susceptible rootstock cultivars would impart these characteristics to the grafted cucumber scions was investigated. Two newly released pumpkin rootstock cultivars used for bloomless cucumber production, ‘Tokiwa Power Z’ and ‘White Power’, were found to be highly resistant to powdery mildew from the seedling stage (tested parts: cotyledons) to the adult stage (tenth true leaves) at cool to moderate temperatures. The accession PPMR-1, a blooming rootstock, showed moderate to high levels of resistance, especially during the adult stage. The conventional bloomless rootstock ‘Hikari Power Gold’ and the conventional blooming rootstock ‘Shin-tosa’ were found to be susceptible. The rootstocks had little to no influence on the resistance to powdery mildew of the grafted scions at younger stages, even though the levels of resistance of the rootstock cultivars differed considerably. Scions, grafted onto PPMR-1 or ‘Shin-tosa’ rootstocks, showed increasing powdery-mildew resistance or tolerance with growth (tested parts: fifth and seventeenth true leaves). The powdery-mildew-resistant ‘Tokiwa Power Z’ and ‘White Power’ did not impart high levels of resistance to scions, whereas ‘Hikari Power Gold’, which is used for bloomless cucumber production, reduced the resistance of scions to powdery mildew. These results indicate that rootstock cultivars, including certain pumpkin rootstocks, e.g., PPMR-1, can alter the powdery-mildew resistance or tolerance of cucumber scions at the adult stage.

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To shorten the breeding cycle in spinach, the effect of photoperiod after bolting on the expression of gynomonoecy was investigated by employing selfed-progeny of a gynomonoecious spinach plant. Seedlings were induced to bolt by an initial exposure to 16-h photoperiod under 140 μmol·m⁻²·s⁻¹ PPFD and 20°C in a growth chamber for 3 weeks after sowing. When transferred to an 8-h photoperiod of the same PPFD, flower stalk elongation and flowering were severely inhibited; the frequency of gynomonoecious plants decreased to about a half of those under 12- and 16-h photoperiods. Under the short-day treatment, a few nodes with hermaphroditic flowers developed; the frequency of hermaphroditic flowers on gynomonoecious plants was 30, 39, and 63% under 8-, 12-, and 16-h photoperiod, respectively. Even when the light intensity under the 8-h photoperiod was doubled, the flower stalks elongated little, while 46% of the plants did not flower. When 8-h photoperiod under 280 μmol·m⁻²·s⁻¹ PPFD was extended to 16-h, by using an incandescent lamp with an intensity of 10 μmol·m⁻²·s⁻¹ PPFD, the seedlings produced flower stalks that were longer than those grown under 16-h photoperiod and 140 μmol·m⁻²·s⁻¹ PPFD, and all plants flowered. There was no difference in the frequency of gynomonoecious plants and hermaphroditic flowers in both 16-h photoperiodic regimes. Extending the photoperiod to 24-h (constant light) from 8-h photoperiod at 280 μmol·m⁻²·s⁻¹ with incandescent lights promoted flower stalk elongation more than did that by extending it to 16-h. However, the frequency of hermaphroditic flowers was almost the same in both the 16- and 24-h photoperiodic regimes. Thus, the expression of gynomonoecy after bolting in spinach was inhibited strongly under a short photoperiod and was promoted significantly by extending the photoperiod to 16-h, but extending the photoperiod to 24-h had no further effect. Therefore, it is important to extend the photoperiod to around 16-h for an efficient production of self-fertilized seeds in gynomonoecious spinach plants during the season with short photoperiods.

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We investigated the ester formation of gypsophila (Gypsophila paniculata L. ‘Bristol Fairy’) inflorescences by exogenously applying several alcohols and determining the substrate specificity of the esterification enzyme, alcohol acetyltransferase (AAT). All exogenous alcohols tested except for ethanol were converted to the respective acetate esters in gypsophila flowers, which indicated that exogenous alcohols, catalyzed by AAT, could react with endogenous acetyl-CoA. Application of isoamyl alcohol facilitated the production of isoamyl isovalerate and consequently decreased emission of methylbutyric acids, which is responsible for the unpleasant odor of gypsophila inflorescences. Some aromatic alcohols, i.e., benzyl alcohol and 2-phenylethyl alcohol, also had similar effects. cis-3-Hexene 1-ol and 1-hexanol were the most reactive alcohol substrates catalyzed by AAT in the cell-free extract, whereas ethanol was the least reactive, indicating that the substrate specificity of AAT in vitro is correlated with that in vivo. That AAT activity in cell-free extracts was already prominent at the bud stage, but decreased when the florets opened suggests that the scarcity of alcoholic substrates is a major factor in limiting volatile ester emission from gypsophila inflorescences.

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The composition and development of inflorescences were compared between a lacecap and hortensia Hydrangea macrophylla (Thunb.) Ser. In this study, we used ‘Blue Sky’ cuttings as lacecap plants and mutated branch cuttings as hortensia plants. The only difference between the inflorescences of lacecap and hortensia was the structure of the upper nodes near the terminal flowers. Partial inflorescences set on the upper nodes of the lacecap, whereas decorative flowers set on the upper nodes of the hortensia. The basic developmental process of the inflorescence was similar in both the lacecap and hortensia. Several pairs of axillary primordia were successively initiated on the inflorescence primordia that were followed by the initiation of terminal flowers. These terminal flowers developed as non-decorative flowers, whereas most axillary primordia developed into partial inflorescences. In hortensia, however, the axillary primordia at the upper nodes differentiated into decorative flowers, which indicates that the change in the inflorescence structure during the mutation from lacecap to hortensia is the replacement of partial inflorescences with decorative flowers on the upper nodes of the inflorescence axes.

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We developed easy, non-destructive methods to investigate the presence of carotenoid and flavonoids in petals by observing them under blue and ultraviolet lights, which are characteristically absorbed by yellow pigments. By using these methods we identified a Eustoma cultivar whose yellow petal coloration was attributed to its carotenoid content. The identification refutes the notion that yellow Eustoma cultivars lack carotenoids. Hence, deep yellow cultivars of this species may be bred in the future. Carotenoids in yellow petals of Eustoma were identified as all-E-neoxanthin, 9′-Z-neoxanthin, violaxanthin, lutein, zeaxanthin and β-carotene. Being different in green bud, most carotenoids occurred as conjugates in open petal, which suggests a stage-specific regulation of carotenoid metabolism. The qualitative and quantitative methods used in this report could be applied to identify other carotenoid-derived yellow flower cultivars in other horticultural species.

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We constructed a genetic linkage map for the carnation (Dianthus caryophyllus L.) on the basis of random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) by using a resistance-segregating population of 134 progeny lines that were derived from a cross between ‘Carnation Nou No. 1’ (a carnation breeding line resistant to bacterial wilt) and ‘Pretty Favvare’ (a susceptible cultivar). The linkage map consisted of 137 RAPD and 9 SSR markers. Linkage analysis revealed that 124 loci could be mapped to 16 linkage groups that extended for 605.0 centiMorgans (cM). The average interval between two loci was 4.9 cM. Quantitative trait loci (QTL) analysis was applied to evaluations of resistance to bacterial wilt that were replicated 8 times. The QTL that we reported previously with a large effect on resistance was detected on group 6 which accounted for 60.5% of the total phenotypic variance with a LOD score 23.46. Two other QTLs with small effects were detected on groups 2 and 5 with LOD scores of 2.32 and 2.87, respectively. These results suggest that resistance to bacterial wilt in carnation is related to one major and at least two minor genes. This study is the first report on the construction of a linkage map of the carnation.

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DC-ACS1 is a gene for 1-aminocyclopropane-1-carboxylate (ACC) synthase which is expressed slightly in the gynoecium, but abundantly in petals of carnation (Dianthus caryophyllus L.) flowers. It is known that ethylene evolved from the gynoecium triggers the expression of DC-ACS1 and DC-ACO1 (the gene for carnation ACC oxidase), which results in an abundant ethylene production in petals. In a transgenic carnation (16-0-66 line) transformed with DC-ACS1 cDNA in sense orientation, the exogenous ethylene treatment caused the expression of DC-ACO1 in the gynoecium and petals, but not that of DC-ACS1. This suggests that the cosuppression of the expression of endogenous DC-ACS1 gene by the integrated transgene. DC-ACS1 transcript is absent in both gynoecium and petals of senescing 16-0-66 flowers, so that the flowers produce no ethylene; whereas DC-ACO1 transcript is present in the gynoecium but absent in the petals. These findings give further support on the role of the DC-ACS1 gene in the gynoecium for ethylene production by petals in senescing carnation flowers.

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‘Rendaiji’ persimmon (Diospyros kaki Thunb.) is a pollination variant astringent type persimmon that is characterized by low levels of the ethylene production rate during ripening. However, a serious problem in postharvest handling is that mature fruits soften quite rapidly accompanied with increased ethylene production after treatments to remove astringency. In this study, we investigated changes in ethylene biosynthesis, by following the accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC) and 1-(malonylamino)-cyclopropane-1-carboxylic acid (MACC), as well as ACC synthase (ACS) and ACC oxidase (ACO) activities and the expression of their respective genes in relation to the process and mechanism of fruit ripening. The response by persimmon fruits to 1-methylcyclopropene (1-MCP) treatments during postharvest ripening was also studied. Ripening was accompanied by relatively low levels of the ethylene production rate, concomitant with a decrease in firmness, especially after exposure to a deastringency treatment by using ethanol vapor. Postharvest application of 1-MCP, on the other hand, did not suppress ethylene production rates to the expected level, but it lowered the accumulation of ACC and the activities of ACC synthase and ACC oxidase. However, the degree of inhibition was higher in ACC synthase, which would imply that the step catalyzed by this enzyme is more subject to regulation by ethylene in this fruit. Comparing gene expression patterns in control and 1-MCP treated fruit by using quantitative RT (Real-Time)-PCR showed that ethylene biosynthesis associated with rapid ripening in ‘Rendaiji’ was accompanied by the expression of DK-ACS1, DK-ACS2, DK-ACO1, and DK-ACO2 genes. The expression of DK-ACS3, however, was not induced.

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Xanthoxin (XAN) in the pulp and seeds of sweet cherry fruit (Prunus avium L.) was identified and quantified by using deuterium-labeled internal standard. The high concentration of total XAN in the pulp was observed in the early stage of fruit development which subsequently declined and remained at a low level until the initial stage of fruit maturation but increased toward harvest. Total XAN concentrations in seeds were high in the immature seed and decreased significantly with seed maturation. Total XAN levels in the immature seeds were approximately 10-times higher than the levels in fruit pulp. This study is the first elucidation of XAN in a non-climacteric fruit.

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‘Kyoho’ grapevine (Vitis × labruscana Bailey) was successfully transformed by Agrobacterium-mediated transformation. Embryogenic calli (EC) were co-cultured with A. tumefaciens strain, EHA105 that harbors a green fluorescent protein (GFP) gene with the CaMV35S promoter. Kanamycin at 15 mg·L⁻¹ was suitable for isolating transformed EC from which three plants that express GFP fluorescence were regenerated. DNA analyses, including polymerase chain reaction (PCR) and PCR-Southern hybridization, confirm that these three plants contain sequences comparable to the GFP gene to indicate that it was successfully incorporated into the ‘Kyoho’ grapevine genome.

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Crossability of Kurume azaleas (Rhododendron obtusum (Lindley) Planch.) as a seed parents, to hybridize with R. japonicum (A. Gray) J. V. Suringar f. flavum Nakai was tested based on the number of viable seedlings per pollinated flower (crossability). The traits of the seed parents, which produced the viable seedlings were recorded. Thirty-nine cultivars of Kurume azalea as seed parents were hybridized with a pollen parent of R. japonicum f. flavum. Seeds derived from 26 out of 39 crosses produced no viable seedling two years after sowing. The remaining 13 crosses yielded 0.2 to 23.2 viable seedlings per pollinated flower, indicating that the difference in the crossing capacity existed among the Kurume azalea cultivars. Stepwise fit and Bayesian approach revealed that the ovules penetrated by pollen tubes (fertilization rate) and the viable seedlings/the seedlings, excluding albinos, (survival rate) were related to the crossability. When the Kurume azalea cultivars possessed morphological leaf surface features which were similar to R. macrosepalum Maxim. and R. ripense Makino, the survival rate and the crossability were high. The data reveal that certain Kurume azaleas can serve as seed parents unilaterally with R. japonicum f. flavum.

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