Cover Gallery
Special Issues

Cover Gallery

Vol.93 (2024)

Vol.93, No.2 (April 2024)

We tried to quantify the relationship between environmental conditions, and yield and quality of cut roses. Three varieties of cut roses with different characteristics were cultured and harvested for three years. Significant negative linear regressions between the interval of flowering flush (growth period) and the mean temperature per growth period were observed. The quality of cut flowers, i.e., stem length, cut flower weight per stem, and specific cut flower weight (the cut flower weight per stem length) was generally negatively correlated with temperature and positively correlated with light intensity. Light intensity also positively affected the total cut flower weight per plant during each growing period. The daily gain in the flower weight of cut flowers per plant (the total cut flower weight divided by the number of days of the growth period) is an indicator of the productivity of the plant; it showed significant positive correlations with the mean daily light integral in three varieties. We believe that such basic analysis is the starting point for the construction of “data-based techniques for crop cultivation”, which has become a hot topic in recent years. (Provided by K. Inamoto: NARO)

Vol.93, No.1 (January 2024)

The Passiflora has 50-60 species that bear edible fruit, P. edulis, P. edulis f. flavicarpa, and hybrids between the two are referred to as passionfruit in a narrow sense. The fruit has many seeds inside a firm pericarp. Each seed is surrounded by succulent edible aril with a complicated structure. The aril has 3 different membranes; an external membrane, an internal membrane with fimbriate structure at the basal area, and a transparent membrane which completely envelops the seed. Kondo and Higuchi in this issue divided the aril into 3 parts, namely the outer pulp (OP), the distal part of the inner pulp (DIP), and the basal part of the inner pulp (BIP), and determined juice quality. The OP included the external membrane and the juice held by the external membrane. The DIP surrounded the seed and the BIP was fimbriate structure. At OP, citric acid content was lower and sugar content was higher than those at DIP, though there were some differences among the varieties. (Provided by T. Kondo and H. Higuchi: Kyoto University)

Vol.92 (2023)

Vol.92, No.4 (October 2023)

Intumescence injury is a physiological disorder that is characterized by abnormal outgrowth of epidermal or parenchymal cells of leaves and commonly occurs in tomato plants. Intumescence occurs under conditions with a lack of ultraviolet irradiance and high relative humidity when cloudy days continue in the greenhouse. Morphological studies found that it occurred along with abnormalities in the cuticular layer, and its severity can be detected by staining the leaves with toluidine blue. O. Sita et al. in this issue showed that the degree of intumescence injury varied among different tomato cultivars. There was a negative correlation between the degree of intumescence injury and the Ca content in tomato shoots. This study suggests that intumescence injury can be mitigated by using cultivars in which intumescence is less likely to occur and increasing the Ca concentration of shoots by providing more Ca nutrients to the plant. (Provided by N. C. Sita and K. Suzuki: Shizuoka University)

Vol.92, No.3 (July 2023)

Abiu is a tropical plant that is well-adapted to Indonesia. Abiu has a self-compatible character, containing 1-4 seeds in each fruit. Abiu is generally propagated using seeds, and the plants will flower around 3 years later. The flowering-to-harvest period is 62–65 days. Abiu belongs to a group of climacteric fruits that experience an increase in ethylene content during ripening. The color of the fruit is green when unripe and turns yellow when ripe, with whitish soft flesh. The total soluble solids (TSS) content ranges from 10–13%, with an acid content ranging from 0.1-0.3%. Abiu has a short shelf life—around 3 days without treatment. A 10 mM exogenous ascorbic acid treatment increased abiu fruit shelf life up to 12 days, nine days longer than the control, as indicated by lower weight loss and browning, a delayed climacteric peak, and also maintaining vitamin C content and fruit firmness. (Provided by S. Susanto: IBP University)

Vol.92, No.2 (April 2023)

Young coconut fruit has become famous recently for its nutritious and refreshing water. To reduce weight for transportation, the husk is often trimmed away and the shell polished, leaving only a cone-shaped husk over the fruit’s stem end. This final product is easy to consume but prone to shell cracking during processing and transport. It is revealed in this research that cracking is due to the strength of the shell, when it is still weak at harvest approximately seven months after anthesis, and where it is thinnest at around midway between the fruit equator and the stylar end, on the largest carpel. In addition, positive internal pressure is another factor responsible for cracking. On the other hand, carbon dioxide accumulating in the water as the coconut grows older was shown to play a limited role in the cracking. It is recommended to delay the harvesting, trimming, and polishing processes to reduce the problem. (Provided by J. Siriphanich: Kasetsart University)

Vol.92, No.1 (January 2023)

The Japanese plum is self-incompatible, and requires cross-pollination for fruit setting. However, extremely low pollen germination rates may cause fruit setting failure. In the special issue ‘Reproductive biology of fruit and nut tree crops’, Takemura et al. show the potential of the Myrobalan plum (flower photo) as a new pollinizer for Japanese plum cultivars. The pollen germination rate in Myrobalan 420-2-2 after 5 h of incubation at 10°C was the highest of all investigated cultivars. In addition, there was no effect of pollination using pollen of Myrobalan 420-2-2 on the development of fruits. In conclusion, our results show that Myrobalan 420-2-2 has the potential to be a new plum pollinizer as it can effectively pollinate the Japanese plum and germinates at low temperatures with no adverse effect on fruit set and quality. (Provided by Y. Takemura and F. Tamura: Tottori University)

Vol.91 (2022)

Vol.91, No.4 (October 2022)

The cover shows the male and female flowers, pollen tubes elongating in the pistil and a split mature fruit of Akebia trifoliata ‘Fuji Murasaki’, a major line in the Asahi-machi region of Yamagata Prefecture, Japan. A. trifoliata is cultivated and bred by selection in a few areas of Japan. The fruit set of A. trifoliata tends to be unstable mainly because of self-incompatibility (SI). A lack of understanding of why Akebia SI occurs hinders successful artificial pollination. Matsumoto et al. in this issue presented experimental data to indicate that SI of A. trifoliata was a late-acting type and that self-pollination would reduce fruit set rather than not contributing to it. This study suggests that excessive self-pollen contamination with artificial pollination may not be desirable for A. trifoliata. (Provided by D. Matsumoto: Fukui Prefectural University)

Vol.91, No.3 (July 2022)

Fruit rapid over-softening is a serious issue in some persimmon cultivars, which not only fundamentally spoils their commercial value, but also can damage the surrounding fruits in transportation. Notwithstanding, it is still hard to predict occurrence of this disorder before softening, even with skilled experts for persimmon fruit sorting. As given in the left two panels on the cover (a fruit over-softened in a few days, and a fruit that maintained its firmness for over 3-weeks), at a glance, we would not be able to easily spot the feature characteristics of rapid over-softening. For quick and non-destructive prediction of this disorder, we attempted to develop a so-called “AI” diagnostic system, based on deep neural network frameworks, with only simple photo images. With 1,080 RGB images of ‘Soshu’ persimmon fruits as the training/testing dataset, three representative convolutional neural networks (CNN) successfully predicted rapid over-softened fruits with >80% accuracy. The prediction values (or confidence for prediction) in the classification were significantly correlated to the date of fruit softening, which would be applicable to the estimation of shelf life. Furthermore, explainable AI (X-AI) techniques, which can back-propagate the trained neural network, visualized relevant regions (or feature characteristics) for the prediction, as given in the right two panels on the cover (color intensity reflects the relevance weight). In other words, they can tell us the predictive symptoms of rapid over-softening, which might be a clue to elucidate the physiological mechanism. By collaborating with X-AIs, we would be able to obtain new perspectives on biological contexts that could not be clarified only with the human eye.
(Provided by K. Masuda, M. Suzuki and T. Akagi: Okayama University)

Vol.91, No.2 (April 2022)

Seed size and number in blueberry (Vaccinium spp.) fruit is one of the important fruit quality components that influence consumers’ eating preference. Fruit containing no or only aborted seeds (for example, ‘Pearl River’, a pentaploid hybrid) and those containing a large number of mature seeds (for example, ‘Sharpblue’) (fruit photo taken by Mr. Naoki Hiraiwa, Kyoto University) possess different texture characteristics that affect consumers’ texture preference. On the other hand, there is an interesting phenomenon related to seed property in blueberry called “metaxenia”, which is the effect of pollen sources on maternal tissues. In the special issue ‘Reproductive biology of fruit and nut tree crops’, Nagasaka et al. provide further evidence of metaxenia in terms of fruit size in highbush blueberry (V. corymbosum ). In addition, they report that the number of mature seeds contributes to metaxenia expression in 14 controlled artificial cross-pollination combinations. To explore the regulation of seed development and the promotional effects of seeds on fruit growth, fruit cell growth in relation to seed development is compared between self- and cross-pollination. In ‘Blue Muffin’ self-pollination, pollen tube reaches ovule (aniline blue-stained pollen tube growth in pistil; photo taken from the master’s thesis of Mr. Shu Ebihara, Kyoto University) but seeds abort probably due to endosperm breakdown during early seed developmental stage (photos taken from Nagasaka et al.). Furthermore, comparative transcriptome analyses suggest that auxin metabolism and signaling activation underpin fruit growth promoted by developing seeds. This study raises the hypothesis that an appropriate pollen source that can activate auxin signaling may contribute to inducing normal seed development and fruit cell enlargement, and provides new insights into the molecular mechanisms underlying metaxenia expression and the potential implications for understanding parthenocarpy expression in blueberry.
(Provided by H. Yamane: Kyoto University)

Vol.91, No.1 (January 2022)

Flower seed production is facing various issues related to climate change. Closed plant production system (CPPS) may be a solution to these issues since the climate inside the system can be fully controlled to match the requirement of an individual plant species for seed production. Using gloxinia (Sinningia speciosa) as a model, we have shown that quality flower seeds, with high germination percentage and seed vigor, can be successfully produced in CPPS, and that artificial light conditions influence some aspects of plant reproductive development and seed production. Scanning electron microscope images revealed that pollen from gloxinia plants grown under 6500 K white light at 200 µmol·m-2·s-1 was much shorter and wider than pollen from those grown under red and blue (RB) lights at the same light intensity after 130 days of cultivation. RB light was found to be superior to white light for gloxinia seed production as it produced plants with compact canopies and larger pollen size, which correlated with greater pollen tube elongation. Results showed that about 0.77 grams of gloxinia seed (approximately 22,000 seeds) can be produced from 1 gloxinia plant grown for 5 months in CPPS.
(Provided by S. Sakhonwasee: Maejo University)

Vol.90 (2021)

Vol.90, No.4 (October 2021)

There is a long-lasting flower trait with a temporal color change, known as “misome-sho”, in Japanese evergreen azalea. This trait has been found in several wild Japanese evergreen azalea species, such as Rhododendron kaempferi ‘Nikkō-misome’, R. macrosepalum ‘Kochō-zoroi’, R. indicum ‘Chōjyu-hō’, and R. × hannoense ‘Amagi-beni-chōjyu’. The corollas of long-lasting flower cultivars undergo a conversion of normal corollas to sepaloid corollas due to loss of function of the MADS-box B class gene, APETALA3 (AP3) homolog. Based on this mutation, DNA markers for the detection of the ap3 mutant allele were developed for each long-lasting cultivar. Also, the long-lasting flower trait was shown to be recessive to normal flowers and controlled by a single gene. The cover picture shows the representative “misome-sho” azalea cultivar, R. kaempferi ‘Nikkō-misome’. The corolla of this cultivar persists more than 100 days and the light pink flower color in anthesis turn greenish in the long-lasting season. In this issue, Gobara et al. indicate that efficient selection of individuals with long-lasting flowers will be possible by using selection DNA markers linked to the long-lasting flower trait, and it has been newly clarified that any combination of different mutant alleles in long-lasting flower cultivars has the long-lasting flower phenotype.
(Provided by N. Kobayashi: Shimane University)

Vol.90, No.3 (July 2021)

A New Root-zone Environmental Control System (N.RECS) has been developed to control the root-zone temperature of horticultural crops, particularly potted plants. N.RECS is composed of heat insulating panels and heat-exchange aluminum panels, and is connected to an air-source heat pump cold/hot water supply system to control root-zone temperature. N.RECS can increase root-zone temperature to approximately 25°C at the minimum air temperature of 5°C in winter, and can decrease root-zone temperature to 20 to 23°C at the maximum air temperature of 35°C in summer. When Fuchsia (Fuchsia × hybrida), which is sensitive to high temperatures in summer, was subjected to root-zone cooling using N.RECS, good growth was noted with little or no death. In winter, lowering greenhouse heating temperature and root-zone heating by N.RECS accelerated growth and flowering of tuberous begonia (Begonia × tuberhybrida) and reduced total heating cost. The integration of root-zone temperature control technology and above-ground environmental control technology will contribute immensely to the further development of modern greenhouse technology.
(Provided by Y. Muramatsu: Nihon University)

Vol.90, No.2 (April 2021)

The picture shows the LED module of an LED artificial sunlight source system*that can produce light at wavelengths of 380–940 nm with a spectral irradiance distribution (SID) of the same level as that of ground level sunlight, with arbitrarily modified SIDs and time-varying (dynamic) light with different SIDs, by application of different voltages to 32 different peak-wavelengths (385–910 nm) LEDs. The LED module has 625 circularly arrayed LEDs within a radius of 66 mm on a printed circuit board. The arrangement of LEDs was determined based on calculations of the number proportion of each type of LED required to produce a SID of the same level as that of ground level sunlight. The LED artificial sunlight source system can facilitate the investigation of plant responses in various static and time-varying(dynamic)light environments. In the picture, some LED light spots are invisible because the wavelengths of the LED light are beyond the visible wavelength range.
(Provided by Kazuhiro Fujiwara,TheUniversity of Tokyo)
*Fujiwara, K., K. Eijima and A. Yano (2013) Second-generation LED-artificial sunlight source system available for light effects research in biological and agricultural sciences. Proc. 7th LuxPacifica, 140–145,Bangkok,Thailand.

Vol.90, No.1 (January 2021)

Japanese pear (Pyrus pyrifolia) is one of the most economically important and attractive fruit crops cultivated in Japan and East Asia. The development of reliable DNA markers, simple sequence repeats, and single nucleotide polymorphisms could help obtain tightly linked DNA markers for selection of resistance to black spot (caused by Alternaria alternata) and pear scab (caused by Venturia nashicola), self-compatibility, harvest time, and fruit skin color in Japanese pear. The combination of these reliable DNA markers and reference genetic linkage maps has enabled practical marker-assisted selection in the Japanese pear breeding program, and selection efficiency has been improved by more than threefold compared with conventional breeding. Japanese pear belongs to tribe Pyreae of family Rosaceae, along with apple (Malus × domestica) and loquat (Eriobotrya japonica). Reliable DNA markers could also identify very good colinearity among all of the 17 chromosomes of pear, apple, and loquat. Colinearity and functional synteny between pear and apple are used to predict the function of a gene of interest and develop selection markers for related species.
(Provided by T. Yamamoto, NARO)

Vol.89 (2020)

Vol.89, No.5 (October 2020)

Onion (Allium cepa L.) is grown using two different cultivation methods (spring-sowing and autumn-sowing) in Japan. In the Tohoku region, the traditional cultivation method for onion production has been autumn sowing. However, onion productivity of this cultivation method in this region has been low. In recent years, spring-sowing cultivation of onion has been established in this region to improve onion productivity. To better understand this new cultivation method, Ikeda et al. examined the plant growth and bulb development of eight commercially-grown onion cultivars throughout the growth period. We showed that this cultivation method enabled us to grow and compare relatively long-day and intermediate-day onion cultivars at the same time, under the same environmental conditions. It is well-known that onion bulb development is induced and persisted during long day-lengths and is inhibited by short day-lengths which were longer or shorter than the critical day-lengths for bulb development of each cultivar. To investigate these phenomena more deeply, we conducted expression analysis of AcFT genes that relates bulb development. This analysis showed that AcFT1 was expressed in accordance with the maturity of the cultivars, and this gene expression can be used as an index for maturity types of the cultivars and bulb development. The results also indicated that onion responds to a critical day-length for bulb development and starts bulb development before the bulbing ratio greatly exceeds 2 which is conventionally used as an indicator of bulb development.
(Provided by H. Ikeda: Tohoku Agricultural Research Center, NARO (previous affiliation))

Vol.89, No.4 (July 2020)

In an attempt to improve dry matter production of tomato plants in a greenhouse, temperature and CO2 concentration, and leaf area index of the plants were managed to meet targets determined based on model predictions. In the model, leaf area and thus the intercepted light is obtained by non-destructive, manual measurements of leaf width and length and the number of leaves. Light-use efficiency is expressed as a function of daytime CO2 concentration since light-use efficiency was significantly correlated with the mean daytime CO2 concentration (UTD-171; Saito et al. pp. 445–453). On the basis of a long-term cultivation experiment for one year, yield improvement to > 50 kg·m−2 per year was succeeded (UTD-170; Saito et al. pp. 425–431). The model can be also applied in a short-term, low-truss crop management. Dry matter production, and light-use efficiency were also investigated during 6 consecutive periods over a year (UTD-143; Itoh et al. pp. 417–424). Light-use efficiency and dry matter production by plants was not reduced by the salinized treatment with high EC solution in the low-truss crops. Thus, without reducing dry matter production, high-brix tomatoes can be produced by controlling the nutrient solution (UTD-148; Itoh et al. pp. 403–409). By using the model, dry matter production and yield of greenhouse tomatoes were predicted with high accuracy from photosynthetically active radiation, temperature, CO2, and manual measurements of leaves in both long-term and short-term crop managements.
(Provided by T. Higashide: Institute of Vegetables and Floriculture, NARO)

Vol.89, No.3 (April 2020)

The simultaneous multi-element analysis (ionomic analysis) is useful to evaluate the role of several nutrients in fruit tree nutrition. Cover pictures show a long-term N fertilization trial that has been conducted for more than 40 years since 1973 at the Fruit Tree Research Center, Fukushima Agricultural Technology Center, Fukushima, Japan. At an apple ‘Jonathan’ orchard with a N fertilized plot (4N plot; up to 20 g N m–2 y–1 as NH4NO3) and an unfertilized control (0N plot), we assessed the effects of continuous N fertilization on the concentrations of 11 elements including macro- and micro-nutrients, and a beneficial element in the tree tissues (Matsuoka et al., 2019). The long-term N fertilization increased N and Mn, and decreased K in both fruits and leaves. The fertilization also increased Zn and decreased B in the fruits. The importance of the simultaneous analysis of multi elements for better fruit production is reviewed by Matsuoka (pp. 197–207).
(Provided by K. Matsuoka: Institute of Fruit Tree and Tea Science, NARO (previous affiliation))

Vol.89, No.2 (March 2020)

Strawberry, one of the most attractive berry crops, has relationship with us in many ways. Selected articles in this issue represents such multi-aspect of this crop, so as the cover image: from laboratory to table. Flowering regulation is a major interest not only for researchers but also for growers, as flowering directly linked to earliness and yield potential of strawberry. This issue covers the history of the development of flowering regulation techniques in Japan, molecular mechanisms of flowering, current status of Fragaria genome research and male sterility to accelerate breeding. New production techniques are also important and articles related how to produce strawberries in sustainable way in field and in plant factories are selected as well. Consumer is another important factor in the strawberry industry so articles of the strawberry allergen and transportation technique to provide good quality fruit to consumers are also included.
(Illustration by Suana Science)

Vol.89, No.1 (January 2020)

Argyranthemum frutescens is a perennial Asteraceae species and one of the most popular pot flowers in spring. Intergeneric hybrids between A. frutescens and Glebionis carinata, an annual plant, have been reported. These hybrids have flower colors and fragrances that differ from those of conventional A. frutescens cultivars. However, they suffer from such problems as poor plant vigor, sparse branching, and poor growth after flowering. Therefore, we carried out crossing with some perennial Asteraceae plants in an attempt to produce robust intergeneric hybrids. This issue (pp. 45–53) reviews recent studies of the production of intergeneric hybrids between A. frutescens and Rhodanthemum gayanum and the development of gene markers for distinguishing the intergeneric hybrids. It also shows the potential of introducing novel traits, such as robustness and cold resistance, into A. frutescens cultivars by using an embryo culture technique. In the cover photo are the flowers and leaves of the intergeneric hybrids between A. frutescens and R. gayanum.                             (Provided by T. Muto: Chiba University)

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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