Cover Gallery

Cover Gallery

Vol.88 (2019)

Vol.88, No.3 (July 2019)

In greenhouse vegetable production, heating and/or cooling are often necessary when temperature exceeds the optimum range for plant growth. As temperature control is a costly process, it is important to develop methods that feature less energy expenditure. In this issue (pp. 305–314), recent studies of local temperature control techniques are reviewed. Roots, fruits, shoot tips, and flowers are generally sensitive to temperature changes, and thus their temperature control should be given primary consideration. The cover figure shows the physiological effects of local heating and cooling of tomato roots, the local heating of cherry tomato shoot tips and flowers in a farm (supported by Bio-oriented Technology Research Advancement Institution, NARO; project No. 17936102) and differences in the vertical distribution of tomato surface temperature between conventional and local heating of shoot tips and flowers.
(Provided by Y. Kawasaki: Western Region Agricultural Research Center, NARO)

Vol.88, No.2 (April 2019)

Carotenoids are responsible for the bright yellow, orange, and red colors of fruits and flowers, and are used as substrates for the synthesis of flavor compounds. Therefore, carotenoids are one of the key determinants of the commercial value of horticultural crops. Carotenoid profiles in green tissues are well conserved. For example, carotenoids essential for photosynthesis, such as lutein and β-carotene, are predominantly accumulated. In contrast, fruits and flowers from different plant species or even the same plant species have diverse carotenoid profiles. The cover photograph shows typical examples of carotenoid diversity in horticultural crops: the major carotenoids in tomato fruit, red pepper, mandarin orange, and chrysanthemum are lycopene, capsanthin, β-cryptoxanthin, and lutein, respectively. Such differences are attributed to a variety of factors, including transcriptional regulation of the carotenoid metabolic pathway, sink capacity, developmental signals, and environmental effects. In this review, we summarize recent advances in studies of the molecular mechanisms that regulate carotenoid accumulation in vegetables, fruits, and ornamental flowers (pp.135–149).
(Provided by A. Ohmiya: NARO)

Vol.88, No.1 (January 2019)

In 2015, the Journal of the Japanese Society for Horticultural Science (JJSHS) was renamed The Horticulture Journal (Hort. J.) to disseminate cutting-edge information on horticultural science research. The Japanese Society for Horticultural Science, which publishes Hort. J., has organized this special issue to further enhance the attractiveness of this journal. The theme of the first special issue is horticultural production restoration efforts in the aftermath of the Great East Japan Earthquake. Numerous people have died or remain missing and a great many were injured. Agricultural land has also suffered extensive damage from the earthquake, tsunami, radioactive materials, and so on. Technological development to restore agricultural production has been initiated and practical farms have been established to demonstrate ways to combine old and new technologies to promote agricultural production. Unfortunately, many of these research and demonstration efforts are recorded in Japanese, making it difficult for many people to fully understand what has been done. Considering that such farmland reconstruction efforts should be useful in the face of a similar disaster in the future, I planned this first special issue of Hort. J. I expect that various special issues of Hort. J. will follow in the future.
(Provided by Y. Yoshida: Okayama University)

Vol.87 (2018)

Vol.87, No.4 (October 2018)

Hydrangeas (Hydrangea spp.) exhibit remarkable characteristics in terms of mechanical reinforcement of decorative sepals. Although decorative sepals at the flowering stage shrink when desiccated, decorative sepals after flowering maintain their shape even after desiccation. In this issue , Kitamura et al.. (pp. 549-556) revealed that axial parenchyma sclerifying in veins after flowering was essential for robust hydrangea decorative sepals and represented a new type of mechanical reinforcement tissue in plant decorative floral organs. In another article (pp. 532-540), investigation focusing on hydrangea flower bud differentiation was reported. Hydrangea flower buds usually differentiate from the end of summer through autumn, but some cultivars can also produce flower buds in spring. Kitamura et al. selected hydrangea cultivars with high potential for such unseasonable flower bud production in Japan by evaluating flower bud production on pinch-treatment-induced axillary shoots. As a result, some cultivars were found to have high potential for unseasonable flowering following pinch treatment in early spring.
(Provided by Y. Kitamura: Shinshu University)

Vol.87, No.3 (July 2018)

In this issue (pp305-314), previous and recent research on anthocyanin biosynthesis in apple fruit is reviewed. The primary anthocyanin in both the skin and flesh of apple fruit is cyanidin 3-galacoside. MdMYB1/10/110a, which encodes a transcription factor, plays a critical role in regulating anthocyanin synthesis in the skin and/or flesh. MdMYB1-1 is the only allele associated with the red skin color and the other alleles do not confer this color, except MdMYB10, an allele of MdMYB1 described below. Individual trees with MdMYB1-1 in a homozygous state bear significantly redder apples than those with the gene in a heterozygous state. This finding enables a marker-assisted selection of individuals with an intensively red skin. Two independent types of MdMYB, MdMYB10 (type 1) and MdMYB110a (type 2), which are responsible for the red coloration of the flesh, have been identified. ‘Geneva’ and ‘Pink Pearl’ apples have the type 1 and type 2 genes, respectively. In both cultivars, a certain amount of anthocyanin accumulates even in the flesh of bagged apple fruit. Since sunlight irradiation is essential for anthocyanin accumulation in the skin of apple fruit, the regulatory mechanism of anthocyanin biosynthesis may differ between the skin and the flesh.
(Provided by C. Honda: The University of Tokyo)

Vol.87, No.2 (April 2018)

Split-pit in peach fruit is a problematic disorder. Split-pit fruit cannot be detected based on external appearance, and contamination of fruit by split-pit reduces its reliability in the marketplace. Here, we demonstrate that split-pit fruit can be identified by a nondestructive acoustic vibration method and a unique approach based on the ratio of the third (f3) to the second (f2) resonant frequency. The response-resonant frequency spectra showed that the peaks of f2 frequencies in split-pit fruit were shifted to much lower values than those in normal fruit, whereas those of f3 frequencies showed only small shifts. The calculated f3/f2 ratios in most normal fruit were in the range of 1.35–1.4, whereas those in split-pit fruit were 1.45–2.0. Analysis of more than 300 fruit samples revealed that by setting the f3/f2 cut-off value at >1.45, 95% of split-pit fruit in the fruit samples were detected, whereas only 1.5% of normal fruit were missorted as split-pit fruit. A model for simulating the vibration properties of peach fruit was developed by using the finite element method. The simulated vibration patterns showed that f3/f2 values were increased by the insertion of split pit, indicating that, at least partially, the observed high f3/f2 values in split-pit fruit directly reflected split-pit occurrence. These results clearly demonstrate that the use of f3/f2 ratios obtained using an acoustic vibration method can effectively detect fruit with split-pit. The possibility of installing acoustic vibration devices in peach sorting lines and the application of portable devices to unpicked fruit on the tree are discussed.
(Provided by R. Nakano et al.: Graduate School of Environmental and Life Science, Okayama University)

Vol.87, No.1 (January 2018)

Because of the commercial importance of grapes (Vitis spp.), it is important to understand how anthocyanin biosynthesis is affected by genetic and environmental factors. In this issue (pp. 1―17), Azuma reviews recent studies of the genetic regulation of anthocyanin biosynthesis in grape berry skin. On the cover, a simple model of the genetic relationship between MYB haplotype composition at the color locus and anthocyanin biosynthesis in the offspring of grape crosses is shown. A summary of environmental factors, such as light and temperature, for anthocyanin biosynthesis in grape berry skin is also provided. In addition, the identification of candidate genes for low-temperature-induced abscisic acid signaling and light signaling networks related to anthocyanin accumulation in grape berry skin by using a grape oligo-DNA microarray is discussed in this review.
(Provided by A. Azuma: NARO Institute of Fruit Tree and Tea Science)

Vol.86 (2017)

Vol.86, No.4 (October 2017)

Sugars are related to fruit yield and quality by playing a critical role in fruit set, growth, ripening, and composition. Not only is tomato (Solanum lycopersicum) an important horticultural crop, it is also a useful experimental model plant. In this issue (pp. 417―425), Kanayama reviews current topics in sugar metabolism and fruit development in tomato, including the use of tomato introgression lines to investigate the control of sugar content, the regulation of sugar metabolism in relation to sugar sensors and signaling, and the roles of proton pumps, sugars, and auxin in fruit set and early fruit development. On the cover, proposed models are shown for the increased sugar and amino acid contents in fruit of IL8-3, a tomato introgression line, and for the roles of sugars and auxin in fruit set and early fruit development. The trade-off between fruit sugar content and yield, and the factors involved in sugar sensing and signaling are discussed as well in this review article.
(Provided by Y. Kanayama: Tohoku University)

Vol.86, No.3 (July 2017)

Lily is one of the most popular flowers and Japanese lilies are important genetic resources for breeding. Lilium auratum var. auratum Lindl. is distributed in the eastern part of Honshu, the main island of Japan. L auratum var. platyphyllum Baker is endemic to the Izu archipelago, which consists of nine large islands located in south of Honshu’s Izu peninsula. L. auratum var. platyphyllum has larger flowers and wider leaves than L. auratum var. auratum. L. auratum var. platyphyllum has yellow spots, whereas L. auratum var. auratum has red or brown ones. Natural hybridization between these two taxa has been suggested on the basis of spot colors of populations in the Izu archipelago and the Izu peninsula. However, their genetic diversity and hybridity in nature have not been reported. Morphological and SSR analyses revealed that L. auratum var. auratum and L. auratum var. platyphyllum are genetically different and that L. auratum var. platyphyllum has genetic diversity among populations in the archipelago. (pp. 379―388)
(Provided by S. Yamamoto : Meiji University)

Vol.86, No.2 (April 2017)

TBreeders and growers are tasked with the production of seedless fruit to meet consumer demand in citriculture. Satsuma mandarin (Citrus unshiu Marc.) is considered to be absolutely seedless because it has both female and male sterility with parthenocarpy. A previous study identified two GA 20-oxidase genes in Satsuma mandarin and confirmed their function using transgenic Arabidopsis. Consistent with the accumulation of active GAs in the ovaries around anthesis, CuGA20ox2 is specifically expressed in the flower bud immediately before anthesis in Satsuma mandarin. In this issue (pp. 183-193), Kotoda et al. characterized Satsuma mandarin GA 2-oxidase genes that encode enzymes with GA inactivation activity, and showed that CuGA2ox4, CuGA2ox2/3, and CuGA2ox8 were differentially expressed in various tissues in Satsuma mandarin and that these genes functioned like GA 2-oxidase genes in transgenic Arabidopsis
(Provided by N. Kotoda: Saga University).

Vol.86, No.1 (January 2017)

The consumption of vegetables and fruits rich in potassium (K), such as melon and strawberry, is restricted in chronic kidney disease (CKD) patients. Therefore, we attempted to produce low-K strawberry through the management of KNO3 concentration in nutrient solution applied from anthesis to harvest period. In this issue (pp. 26-36), Mondal et al. observed a general trend of decreasing K content in four strawberry cultivars with the decrease of KNO3 concentration in the nutrient solution. ‘Toyonoka’ fruit exhibited a K reduction of approximately 64% when plants were grown in nutrient solution containing KNO3 at 1/16 of the normal level. Citric acid and ascorbic acid contents in ‘Toyonoka’ fruit were reduced with decreasing KNO3 concentration in the nutrient solution. Although the reduced NO3− in the nutrient solution was adjusted by adding Ca(NO3)2 to grow low-K strawberry, both yield and quality did not vary with this adjustment. Fruit K content was decreased by 43% and 54% in plants grown in nutrient solution containing 1/8 and 1/16 of the normal level of KNO3, respectively.
(Provided by T. Asao, Shimane University)

Vol.85 (2016)

Vol.85, No.4 (October 2016)

Prunus fruit tree species exhibit S-ribonuclease (S-RNase)-based gametophytic self-incompatibility (GSI). The S-RNase-based GSI system is also found in families Plantaginaceae and Solanaceae and tribe Maleae in family Rosaceae. In these plant taxa, S-RNase and F-box protein are commonly identified as pistil and pollen S determinants, respectively. Interestingly, Prunus GSI was gradually recognized to show distinct features, which is indicated to be attributable to the different molecular functions of its pollen S determinant (S haplotype-specific F-box protein, SFB). It has been suggested that SFB functions in inducing self S-RNase cytotoxicity within pollen tube cytoplasm to inhibit pollen tube growth in self styles, in contrast to pollen S determinant F-box proteins in non-Prunus taxa that function in the detoxification of non-self S-RNases to maintain pollen tube growth in non-self styles. In this issue (pp. 289-305), Matsumoto and Tao summarize the characteristics of Prunus S-RNase-based GSI with references to those of non-Prunus taxa, and suggest a working model for its distinct self/non-self discrimination mechanism.
(Provided by R. Tao: Kyoto University)

Vol.85, No.3 (July 2016)

Next to standard-type chrysanthemum production, the production of cut flowers of small-flowered spray-type chrysanthemum is the largest in Japan, exceeding that of rose or carnation. Because small-flowered spray-type chrysanthemums are used in many religious festivals, their demand increases in certain months of the year. Sales of these flowers in July to September account for about 40% of annual sales. During the high-demand months, summer-to-autumn-flowering small-flowered spray-type (SAFS) chrysanthemums are produced. Therefore, SAFS chrysanthemums are commercially important. However, under current cultivation methods, spray formation quality is compromised in order to maintain sufficient production during the months of peak demand for SAFS chrysanthemums. In this issue (pp. 264-271), Mori et al. showed that spray formation in SAFS chrysanthemum cultivars ‘Haruka’ and ‘Subaru’ could be regulated by controlling the timing and period of interrupted lighting. This technique would enhance the production of various types of spray formations while using the same cultivar, thereby allowing growers to meet various demands while using only a few cultivars. This would stabilize the production of SAFS chrysanthemum cut flowers.
(Provided by Y. Mori: Okayama Prefectural Technology Center for Agriculture, Forestry and Fisheries)

Vol.85, No.2 (April 2016)

Bicolor flowering dahlia (Dahlia variabilis) consists of cultivars having petals with colored bases and white tips. A prominent feature of bicolor dahlia cultivars is the lability, or instability, of petal colors: Instead of producing the original bicolor petals, the cultivars frequently produce single-colored petals without white tips. The red–white bicolor flowering cultivar ‘Yuino,’ which predominantly produces inflorescences with only bicolor petals, often produces inflorescences with only red petals or mixed inflorescences with both red petals and bicolor petals. In this issue (pp. 177-186), Ohno et al. reveal a strong relationship between inflorescence color and flavonoid accumulation in leaves: red-petal-producing plants accumulated flavonoids in leaves, whereas plants producing only bicolor petals tended to not accumulate flavonoids in leaves. This indicates that petal color lability can be interpreted as a phenotypic change at the whole-plant level.
(Provided by S. Ohno : Kyoto University)

Vol.85, No.1 (January 2016)

Cytoplasmic male sterility (CMS) is a useful system for hybrid seed production in crop species. In eggplant, CMS systems have been developed utilizing the cytoplasm of wild Solanum species by repeated backcrossing. The CMS systems are classified into two types. The first one is anther indehiscent-type sterility (second from left of bottom photographs) in which anther contains normal pollen but does not open to release. The second one is pollen non-formation-type sterility (fourth from left of bottom photographs) in which anther of male-sterile lines is completely devoid of pollen. In this issue (pp. 1–7), Khan and Isshiki describe cytoplasmic male sterility in eggplant, focusing on its development, characterization, and fertility restoration, as well as the development of a SCAR marker linked to Rf genes.
(Provided by S. Isshiki : Saga University)

Vol.84 (2015)

Vol.84, No.4 (October 2015)

Transposable elements (TEs) are mobile genetic elements in the eukaryotic genome. TEs are divided into class I (retrotransposons) and class II (DNA transposons). Retrotransposons are especially abundant in higher plant genomes. As retrotransposon insertions with high copy numbers are dispersed throughout these genomes and are inherited genetically, insertion polymorphisms among crop cultivars have been used as molecular markers. Recently, we have developed an efficient method of screening long terminal repeats (LTRs) of retrotransposon families that exhibit high insertion polymorphisms among crop cultivars using a next-generation sequencing (NGS) platform. In addition, we have identified the insertion sites of these identified retrotransposon families on the genome-wide scale in several cultivars with a NGS platform, which enabled us to acquire several molecular markers for DNA genotyping. Among these insertion sites, cultivar-specific insertion sites can be utilized as molecular markers for cultivar discrimination. Our results indicated that the targeted sequencing of retrotransposon insertion sites was highly effective for DNA genotyping and marker development without requiring any whole-genome sequence information. In our review (pp. 283–294), we describe the development of retrotransposon-based molecular markers with the NGS platform in several plant species such as strawberry, citrus, apple, and sweetpotato.
(Provided by Y. Monden: Okayama University)

Vol.84, No.3 (July 2015)

Light and temperature are important environmental factors that affect flavonoid accumulation in grape berry skin. However, the components of light signaling and low-temperature-induced abscisic acid (ABA) signaling networks related to flavonoid biosynthesis have not been fully elucidated. In this issue (pp. 214–226), Azuma et al. discuss how they utilized a grape oligo-DNA microarray (38,549 independent probes) that adopts the publicly available genomic sequence of grape to perform a comprehensive transcriptome analysis of detached grape berries cultured under different light and temperature conditions. Using microarray data, the authors identified 40 light-inducible genes, 55 low-temperature-inducible genes, and 34 light- plus low-temperature-inducible genes. From the expression characteristics of three candidate genes, the authors hypothesized that elongated hypocotyl 5 (HY5), open stomata 1 (OST1), and enhanced response to ABA 1 (ERA1) might be involved in flavonoid biosynthesis via light signaling and low-temperature-induced ABA signaling. In addition, the extensive catalog of gene expression patterns defined in their study will support future investigations of other grape berry skin candidate genes that respond to light and temperature.
(Provided by A. Azuma: NARO Institute of Fruit Tree Science)

Vol.84, No.2 (April 2015)

Genetic transformation approaches have been taken for the functional analyses of cloned genes involved in flavonoid biosynthesis. In such studies, both homologous and heterologous plants have been used as hosts for the genetic transformation. Examples include petunia, torenia, Nicotiana, and Arabidopsis. In this issue (pp. 131–139), Takatori et al. utilized Ipomoea nil (Japanese morning glory) as the heterologous host for the transgenic complementation (right) of the flavonoid 3′-hydroxylase (F3′H) gene cloned from Eustoma grandiflorum (lisianthus; upper left), because an authentic magenta mutant of this species, I. nil ‘Violet’ (lower left), has a deficient F3′H gene. The authors demonstrated that the lisianthus F3′H gene encodes a functional flavonoid 3′-hydroxylase. In addition, their study underscored the use of I. nil as a valuable model organism for molecular genetic studies of flower pigments. This is the first report of both the cloning of the lisianthus F3′H gene and the transgenic complementation using a heterologous host of Japanese morning glory carrying a mutant allele of the corresponding gene.
(Provided by K. Shimizu: Kagoshima University)

Vol.84, No.1 (January 2015)

The carnation is a very popular gift on Mother’s Day and other occasions. Along with chrysanthemum and rose, carnation is one of the most commercially important ornamental crops in Japan and around the world. To produce new cultivars efficiently and speed up breeding, linkage analysis and the development of markers for bacterial wilt resistance derived from line 85-11 and Dianthus capitatus ssp. andrzejowskianus had been conducted (lower). Recently, the genome sequencing of ‘Francesco’ (upper left), the leading carnation cultivar in Japan, was conducted and the results were made available in the sequence database (upper right). In this issue (pp. 3–13), Yagi describes recent advances in the genome analysis of ornamental plants, with focus on carnation. Genome sequencing analysis of other ornamentals is expected in the near future. Such advances mark the beginning of a new era in the breeding of ornamentals.
(Provided by M. Yagi: NARO Institute of Floricultural Science)

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