In this study, a set of seven simple sequence repeat (SSR) markers were developed for Japanese maple, and the genetic diversity of 107 Japanese maple cultivars was estimated using these markers. A total of 87 alleles were detected, ranging from 4 to 25 per locus, with an average of 12.43 alleles per locus. Most cultivars showed unique SSR profiles, indicating that the markers were effective for cultivar identification, while some pairs of bud-sport cultivars and synonyms showed identical SSR profiles. Principal component analysis (PCA) indicated that 107 Japanese maple cultivars were divided into two groups: one consists of cultivars of Acer palmatum, and the other group includes cultivars of two varieties, A. amoenum var. amoenum and A. amoenum var. matsumurae. Analysis of molecular variance (AMOVA) revealed significant differentiation between the two species, while the genetic differentiation and distance between the two varieties of A. amoenum were very low, with F_ST = 0.026 and D = 0.057, respectively. Thus, the two varieties of A. amoenum are genetically indistinguishable from each other in domesticated cultivars, while most cultivars of A. palmatum have been developed separately from those of A. amoenum.

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The majority of ornamental camellia cultivars are derived from Camellia japonica. Camellia japonica subsp. rusticana, C. sasanqua, and C. reticulata have also been utilized. The four species/subspecies and their hybrids form the majority of modern camellias; however, some cultivars may have arisen from other species because of their unique morphological and physiological characteristics. Based on these characteristics and the location where it was discovered, ‘Robiraki’ was considered to be a natural interspecific hybrid between C. sinensis and C. japonica subsp. rusticana. Molecular analyses indicated that the seed parent was C. japonica or C. japonica subsp. rusticana. ‘Tagoto-no-tsuki’, thought to be one of the sasanqua cultivars, was assumed to be derived from the native Chinese species C. oleifera based on the morphological characteristics. Chloroplast DNA shows maternal inheritance in the genus Camellia. PCR-RFLP analysis using chloroplast DNA of the atpI-atpH region digested by TaqI and the trnL-trnF region digested by TasI (TspEI) can distinguish C. japonica from C. japonica subsp. rusticana and C. sasanqua from C. oleifera. Here, we conducted PCR-RFLP analyses, and found coincident polymorphisms between ‘Robiraki’ and C. japonica subsp. rusticana and between ‘Tagoto-no-tsuki’ and C. oleifera, respectively. Because the DNA sequences of the atpI-atpH region also coincided respectively, we concluded that the maternal ancestor of ‘Robiraki’ is C. japonica subsp. rusticana, and that of ‘Tagoto-no-tsuki’ is C. oleifera.

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Monoecious melon cultivars have several advantages, such as a low cost and high efficiency of seed production. Melon breeders in Japan, however, have been hesitating to introduce a monoecious trait to melon cultivars for fear of an unsuitable elongated fruit shape and low sugar content. The effect of a monoecious trait on the fruit shape and total soluble solid contents in the Japanese Earl’s type melon was studied using: 1) an F₂ population derived from a cross between an andromonoecious ‘Earl’s Favourite Harukei 3’ and a monoecious M09- ♀ 1, and 2) genetically similar background lines of an andromonoecious M03-7 and monoecious lines of M09- ♀ 1 and M09- ♀ 2. The fruit shape of monoecious F₂ plants was clearly longer than that of andromonoecious F₂ plants. As for the total soluble solid contents, monoecious F₂ plants showed clearly lower levels than andromonoecious F₂ plants. However, the distributions of the fruit shape and total soluble solid contents in F₂ plants were wide. F₂ plants with a nearly globular shape or higher total soluble solid content were found in this study. A difference between homozygous and heterozygous plants for a monoecious gene was slightly observed only in the total soluble solid contents and not in other traits such as the fruit shape. There was no difference in the accumulation pattern of total soluble solid contents among the andromonoecious and monoecious lines. Judging from these results, it was suggested that there is possibility of selecting a plant with a globular shape fruit and a higher sugar content through using a large segregating population. We also discussed the availability of monoecious oval/oblong fruit in the food service industry.

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The relationship between the flower color and anthocyanin composition of petals was investigated in 13 cultivars of Leschenaultia species and interspecific hybrids. Five anthocyanins, including cyanidin 3-glucoside (Cy 3G) and cyanidin 3-(6-malonyl)-glucoside (Cy 3MG), which have never been reported in Leschenaultia, were identified. Major anthocyanins of petals were Leschenaultia Blue Anthocyanin 1 (LBA 1), demalonyl LBA 1 and LBA 2 (Saito et al., 2007) in cultivars with blue and violet-blue flowers, and Cy 3G and Cy 3MG in those with red and red-purple ones. Regarding the flower color from yellow-orange to red-purple, decreases in the hue values (b*/a*) of these flower colors were responsible for decreasing carotenoids and increasing Cy 3MG and Cy 3G.

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Oriental persimmons (Diospyros kaki Thunb.; 2n = 6x = 90) are classified into four types depending on the astringency loss on the tree and its influence by seed: pollination constant non-astringent (PCNA), pollination variant non-astringent (PVNA), pollination variant astringent (PVA), and pollination constant astringent (PCA). Among these types, PCNA is the most important for breeding because its fruits show a stable loss of astringency on the tree. Two PCNA types, Japanese PCNA (J-PCNA) and Chinese PCNA (C-PCNA), have originated independently in Japan and China, respectively, and astringency loss in fruits of these types is controlled by different genetic mechanisms. In this study, we studied the relationship between the C-PCNA trait and fruit shape in progenies of the C-PCNA cultivar ‘Luo Tian Tian Shi’ × ‘Yotsumizo’ (PCA), ‘Iwasedo’ (PCA), and ‘Okugosho’ (J-PCNA). Since no J-PCNA offspring are yielded theoretically, all PCNA offspring are assumed to be the C-PCNA genotype. The fruit shape index, longitudinal diameter, and seed length were significantly greater in the PCNA than in the non-PCNA offspring. Fruits of the PCNA offspring have a flatter shape than those of the non-PCNA offspring. In contrast, the transverse diameter was not significantly different between the PCNA and non-PCNA progenies. The average fruit weight was larger in the PCNA than in the non-PCNA offspring, in which the difference was not significant. The length of the minor axis of the parenchyma cell in the fruit showed no significant difference between the PCNA and non-PCNA offspring, but fruits of the PCNA offspring had approximately 10% significantly smaller cells in the major axis and total area of the parenchyma cell. These results suggest that the C-PCNA fruit is repressed and/or reduced in terms of longitudinal growth of the fruit cell. The prevention of proanthocyanidin accumulation in the fruit may possibly have been an indirect effect on fruit growth. In addition, since ‘Luo Tian Tian Shi’ has only one dominant allele for the PCNA trait, the neighboring locus may have a strong effect on the trait that represses longitudinal growth of the fruit.

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In order to maintain tree vigor under sheet multi-cultivation conditions, we used the soil moisture management index to identify optimal conditions for improving the roots of Satsuma mandarin ‘Ishiji’. During the first root growth period (from May to July), the greatest increase occurred under pF1.8 conditions, followed by pF2.3 and pF2.8. Under the pF1.8 condition, high-quality fruits were produced, which was satisfactory from the standpoint of fruit production. During the second root growth period (from August to September), the greatest increase occurred under pF1.8 conditions, followed by pF2.3 and pF2.8. However, under the pF1.8 condition, the sugar content after harvesting and processing was low. In contrast, under the pF2.3 condition, the second longest root growth and high-quality fruits, with the sugar content exceeding 12.0°, were produced. This was also satisfactory from the standpoint of fruit production. In conclusion, pF1.8 is the optimal soil moisture management index for root growth in Satsuma mandarin ‘Ishiji’ from May to July, whereas pF2.3 is the optimal soil moisture management index from August to September.

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Soil diagnosis was used to reduce the amount of nitrogen fertilizer and plant nitrate concentration in a year-round cultivation of komatsuna (Brassica rapa L. Perviridis Group) in a greenhouse. The amount of nitrogen fertilizer in the control was based on the plant-assimilated nitrogen. The soil nitrate-nitrogen content was tested before fertilization and subtracted from two standard amounts of nitrogen fertilizer. That in Method-I was the amount of the control, and the amount of nitrogen mineralized from the soil in Method-II was subtracted from the amount of the control. Total amounts of nitrogen fertilizer used during the five seasons were 20.0, 9.5, and 4.4 g·m⁻² for the control, Method-I, and Method-II, respectively. At lower temperatures, the plants grew slowly and the amount of nitrogen from the soil was lower. Yields were similar with all methods, although the leaves were paler than in the control with Method-I and II during spring and summer. The plant nitrate concentration with all methods was <1,000 mg·kg⁻¹ during winter and spring; with the control, it was >2,500 mg·kg⁻¹ in summer and autumn; and with Method-I and II, it was <500 mg·kg⁻¹ in summer and approximately 2,300 and 800 mg·kg⁻¹, respectively, in autumn. These results indicate that both methods reduced the amount of nitrogen fertilizer and plant nitrate concentration.

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Even though the corollas abscise at the base of the flower at anthesis, the corollas of some grape cultivars remain on their ovaries for a while. The retention of corollas can lead to the russeting of berries, especially in ‘Sun Verde’, whose long ovary, narrow corolla, short filaments, and incomplete corolla dehiscence make it hard to remove the corollas. We investigated the effectiveness of 3 types of radial brush fixed to the top of a dipping cup to dislodge the corolla during the 1st gibberellin treatment. Three days after gibberellin treatment, the rate of corolla fall in brushed grapes was 2 to 3 times that in the control (unbrushed) grapes. The removal of all corollas by hand led to the lowest occurrence of severe russeting at maturity, followed by brushing, and non-removal in ‘Sun Verde’ grape. Brushing significantly decreased the incidence of severe russeting relative to the control.

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We investigated alternative portable methods to the rheometer in fruit firmness evaluation for high functional or aroma components of processed Japanese apricot liqueur (ume liqueur) of ‘Nanko’ Japanese apricot (Prunus mume Sieb. et Zucc.). Fruit firmness using the universal hardness meter showed a difference based on the harvesting time and fruiting position, although there was little difference using the rheometer. The elasticity index (EI) using the portable vibration hardness meter was also able to evaluate these differences as well as the universal hardness meter. EI was more significantly correlated with the rheometer than the universal hardness meter. There was little difference between EIs calculated based on the fruit diameter and mass. EI calculated by f₂²·d² (Ed f₂), where f₂ was the second resonant frequency and d was the fruit diameter, showed a higher correlation with the firmness obtained from the rheometer than EI calculated by f₃²·d² (Ed f₃), where f₃ was the third resonant frequency, in both developing and ripening fruit. Therefore, Ed f₂ should be suitable for determining the firmness of Japanese apricot fruit as a substitute for the rheometer. The time of a sharp decrease in fruit firmness, the index of the time when functional components reached high levels in ume liqueur for the rheometer, was not detected by either the universal hardness meter or portable vibration hardness meter. However, the ume liqueur made from fruit with below 10,000 in Ed f₂, 17,000 in Ed f₃ or 2.2 kg using the universal hardness meter with a 3-mm-diameter cylindrical plunger, contained higher functional components. These results suggest that the portable vibration hardness meter is suitable for the nondestructive measurement of fruit firmness, and might be available for calculating the index of raw material fruit to process ume liqueur with high functional components or aroma components in Japanese apricot ‘Nanko’.

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The chrysanthemum cultivar ‘Natsubiyori’ was raised by cross combinations between a summer-to-autumn flowering chrysanthemum line, Seiun 96-2, with white flower heads as the seed parent, and other summer-to-autumn flowering lines with white flower heads as pollen parents. The first cultivar generated with yellow flower heads has no malformed flowers (i.e., proliferate flowers) when grown under high-temperature conditions in the summer, and can be shipped from June to September using a long-day treatment with incandescent lamps. Because the plant consists of a rosette habit, flowering was faster and the cut-flower length was longer when stock plants were exposed to natural low temperatures from late October until early January compared with stock plants grown at a constant temperature of 15°C from late October until early February. The number of days to flowering after the end of the long-day treatment was 63–78 according to the cropping type. The optimum day length for flowering was 12 hours, and maintaining plants in the shade was appropriate for transport during July to September.

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Growth-retarding factors of asparagus (Asparagus officinalis L.) cultivated in an open field were analyzed. Twenty tensiometers were set at a 15-cm depth in five ridges to monitor the response of the soil water matric potential after rainfall. In the ridges with healthy asparagus plants, the soils dried steadily. On the other hand, in the ridges with asparagus plants of a shorter plant height, with a thinner width and yellowish stems and cladodes, the soil water matric potential remained extra-wet (more than field capacity: −9.8 kPa) even a week after rainfall. Although the reasons for differences in soil water matric potentials at a 15-cm depth among ridges are unknown, this study suggests that monitoring soil moisture conditions using a tensiometer at a 15-cm depth can be effective to estimate risks causing the unhealthy growth of asparagus. For promoting the intensive production of asparagus in an open field, especially in a drained paddy field, further studies are necessary to clarify factors influencing the wet conditions of soil.

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We examined the morphological features of lusterless tomato fruit occurring in southern Hokkaido, Japan and its discrimination method. A light was diffused on the epicarp of lusterless fruit in the dark. While sections of the epicarp surface of normal fruit were smooth when observed under a microscope (×100), those of the lusterless fruit were rough. Polygonal cells were observed on the surface of the normal fruit epicarp by the SUMP method (×100). Additionally, cracks were seen on the surface of the lusterless fruit. We believe that the cracks form the rough epicarp, diffusing light when irradiated, and cause the loss of luster as well as the rough texture. The water content of the lusterless fruit was less than that of normal fruit after harvest, and lusterless fruit had an inferior shelf life.

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The effects of changed night temperature setting (10 to 15°C) in winter on the flowering, yield, and form of spray-type carnations (Dianthus caryophyllus L.) were investigated. Spray-type carnation cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ were planted in four greenhouses on June 27, 2008, pinched on July 18, and pinched again on September 5. The night temperature in the greenhouses was kept at 10°C from November 20. It was changed to 15°C from December 1, January 9, or February 18, in three night temperature-changed treatments, or maintained at 10°C throughout the experimental period (control). All treatments were continued until April 30. Three primary lateral shoots were not influenced by the night temperature in winter because they were harvested until December. In both cultivars, the number of days from pinching to flowering decreased in secondary lateral shoots that sprouted from decapitated primary shoots. The yield of cut flowers between January and March increased as the night temperature increased from December 1. Therefore, the total yield of cut flowers paralleled that from January to March. The length and weight of cut flowers showed a tendency to decrease at a 15°C night temperature. In ‘Light Pink Barbara’, the number of florets also showed a decreasing tendency at 15°C. In ‘Cherry Tessino’, the diameter of florets showed a decreasing tendency as the night temperature increased from December 1. As the results, high quality cut flowers were produced in all treatments when the night temperature was elevated to 15°C. In conclusion, it was shown that the change of the winter night temperature to 15°C from December 1 increased the yield of cut flowers in winter of spray-type carnations cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ while maintaining a high cut flower quality.

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To reveal whether the growth of potted flowers is regulated by the root-zone temperature, the effect of root-zone temperatures on the growth of potted flowers such as Verbena × hybrida and Pelargonium × hortorum was investigated using a root-zone environmental control system (RECS). When Verbena × hybrida plants were grown under 15, 20, and 25°C root-zone temperatures (RZT), the growth of the top was markedly promoted at 25°C RZT, and dry weight of the whole plant at 25°C RZT increased ca. 1.5 times compared to that of 15°C RZT. In addition, the potted flowers of Pelargonium hortorum were grown with non-heating, 13°C heating, and 18°C heating of root-zones with an 8°C minimal air temperature during the winter season. The growth of the top, flowering rate, and number of florets increased with 18°C heating, and the dry weight of the whole plant increased ca. 2 times compared to that of non-heating. In conclusion, it was revealed that the growth of potted flowers could be controlled by RZT using RECS.

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To develop practical flowering-acceleration techniques for summer-to-autumn flowering small-flowered spray type chrysanthemums harvested in August, the effects of gibberellic acid (GA) application after the flower budding stage on the flowering and cut flower quality were investigated. In experiment 1, GA application (50 or 100 ppm, 2 or 3 times) for ‘Sansui’ was started at the terminal flower budding stage. In almost all GA applications, flowering of the second lateral flower accelerated, and the flower cluster and pedicel lengths increased. In experiment 2, GA application (100 or 200 ppm) for ‘Sansui’ and ‘Kurenai’ was started at the flower budding, 10 days after budding, and bud break stages. Flowering accelerated in almost all GA applications. Flower cluster and pedicel lengths increased with GA application at the flower budding and 10 days after budding stages but were not affected at the bud break stage. In experiment 3, GA application (100 or 200 ppm) was started when the terminal flower bud diameter was 3.5 (flower budding), 6, and 8.5 (bud break) mm, respectively. Flowering accelerated in all GA applications. Flower cluster and pedicel lengths increased in GA application at 3.5 and 6 mm diameters, but were not affected at 8.5 mm. Therefore, GA application (100–200 ppm, twice) after the bud break stage accelerates flowering without reducing the cut flower quality.

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The cause of internal black spot of cabbage has been speculated to be cold damage. However, in this study, we hypothesized that an acute temperature increase in the cabbage head can also be a cause, and conducted a detailed analysis on temperature change inside the cabbage head leaves and the effect of the formation of ice. Inside the cabbage leaves in winter, water droplets often froze and formed ice. Under sunny conditions, the temperature inside the cabbage leaves rose very quickly, and cell death occurred. When ice formation was induced at −5°C, cell death was induced within 60 min in all tested samples. Cell death was confirmed by tripan blue staining. Thus, we concluded that rapid thawing of frozen leaves by an acute temperature increase inside cabbage head leaves can cause damage to the cells, resulting in internal black spot.

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