The Horticulture Journal
Online ISSN : 2189-0110
Print ISSN : 2189-0102
ISSN-L : 2189-0102
Advance online publication
Showing 1-25 articles out of 25 articles from Advance online publication
  • Takuya Wada, Masao Tsubone, Miyuki Mori, Chiharu Hirata, Shiro Nagamat ...
    Type: Original Articles
    Article ID: UTD-180
    Published: 2020
    [Advance publication] Released: June 27, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Cultivated strawberry is one of the important commercial fruits not only in Japan, but around the world. Even so, analyzing regions responsible for fruit quality traits of cultivated strawberry has been very challenging due to the alloploidy and octoploidy of genome conformation. In order to solve this problem, we previously developed a strawberry multi-parent advanced generation inter-cross (MAGIC) population derived from crosses involving six cultivars. Here, we performed genotyping of the MAGIC population with simple sequence repeat (SSR) markers, which were generated from an expressed sequence tag site, and conducted a genome-wide association study of 13 strawberry fruit quality-related traits to reveal associated quantitative trait loci (QTLs). Correlation coefficients among fruit color-related traits, such as fruit surface color (FSC), fruit surface anthocyanin content (FSA), and fruit flesh anthocyanin content (FFA) were relatively higher, but FSC, FSA, and FFA did not show any higher correlation with other traits. Fruit weight (FW), FSC, and fruit firmness, including whole fruit firmness (WFF), fruit surface firmness (FSF), and fruit flesh firmness (FFF), indicated higher year to year correlation coefficients than other fruit quality-related traits. Among FW, FSC, and WFF, there were only two QTLs for FW, five for FSC, and 38 for WFF (the most) and they were detected on all chromosomes. QTLs for some traits shared common flanking simple sequence repeat markers, and allelic differences of one marker affected the variation of other traits. QTLs for fruit firmness were most frequently detected, followed by those for SSC and titratable acidity (TA). Allelic differences in these QTLs negatively affected FSC, the fruit surface anthocyanin content (FSA), and fruit flesh anthocyanin content (FFA), implying that alleles which increase fruit firmness, SSC, and TA lighten fruit color. Similarly, QTLs for FSC, FSA, and FFA mostly negatively affected FSF, FFF, SSC, and TA and did not affect WFF. This indicated that simultaneous improvement in fruit firmness, SSC, and TA is possible with many markers, but improving fruit firmness and deepening fruit color are highly challenging.

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  • Hiroki Ikeda, Takehiko Yamamoto, Takafumi Kinoshita, Hikaru Tsukazaki, ...
    Type: Original Articles
    Article ID: UTD-200
    Published: 2020
    [Advance publication] Released: June 27, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Onion (Allium cepa L.) is one of the most important vegetable crops worldwide. In Japan, it is grown using two different cultivation methods (spring-sowing and autumn-sowing). The traditional cultivation method for onion in the Tohoku region in northeast Japan has been autumn sowing; however, onion productivity has been low. Recently, spring sowing of onion has been established in this region to improve onion productivity in the off-crop season. To better understand the spring-sowing cultivation method, we examined the plant growth and bulb development of eight commercially-grown onion cultivars (‘Turbo’, ‘Aurora’, ‘Momiji No. 3’, ‘Marso’, ‘Okhotsk 222’, ‘Kitamomiji 2000’, ‘Super Kitamomiji’, and ‘Gunnison’) throughout the growth period. The results showed that this cultivation method enabled us to grow and compare relatively long-day and intermediate-day cultivars at the same time, under the same environmental conditions. Onion bulb development was induced and persisted during long day-lengths and was inhibited by short day-lengths which were longer or shorter than the critical day-lengths for bulb development of each cultivar. To elucidate this mechanism, expression analysis of AcFTs related to bulb development was conducted. Our expression 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 indicate that onion responds to a critical day-length for bulb development and starts bulb development before the bulbing ratio greatly exceeds 2. This metric can be used as an index of bulb development.

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  • Ayako Katayama-Ikegami, Zion Byun, Suzuka Okada, Masahiro Miyashita, T ...
    Type: Original Articles
    Article ID: UTD-201
    Published: 2020
    [Advance publication] Released: June 27, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Red mangos (Mangifera indica L.) accumulate appreciable amounts of cyanidin-based anthocyanins in the skin, and previous studies showed that these anthocyanins contain galactose as a sugar moiety. To date, two UDP:flavonoid 3-O-glycosyltransferase (UFGT)-like genes named MiUFGT1 and MiUFGT3 (MiUFGalT3) have been isolated from mango ‘Irwin’ peel as anthocyanin-related UFGT genes, but the function of the proteins of the genes have not yet been elucidated. In this study, we characterized recombinant MiUFGT1 and MiUFGalT3 expressed in Escherichia coli. In the presence of quercetin as an acceptor, rMiUFGT1 showed marginal glucosylation activity, while rMiUFGalT3 exhibited significant galactosylation activity 20-fold higher than its glucosylation activity. Specificity analysis using purified MiUFGalT3 found that rMiUFGalT3 almost equally accepts anthocyanidins and flavonols. The anthocyanins extracted from the ‘Irwin’ skins were cyanidin 3-O-galactoside and 7-O-methylcyanidin 3-O-galactoside by instrumental analyses, which is consistent with previous results obtained for other red mango cultivars. The results suggest that MiUFGalT3 is responsible for the red coloration of ‘Irwin’ mango fruit skins.

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  • Yoshihiro Nakano, Tomoyuki Takase, Katsuhiko Sumitomo, Shihori Suzuki, ...
    Type: Original Articles
    Article ID: UTD-192
    Published: 2020
    [Advance publication] Released: June 20, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Heat-induced flowering delay of Chrysanthemum morifolium is a major problem affecting the production of cut flowers in Japan. Understanding the delay mechanism is indispensable to achieve stable production. Heat sensitivity has been shown to fluctuate throughout the day, as if it is regulated by a circadian clock. This paper studied the involvement of a circadian clock and photoperiod in the fluctuation of heat sensitivity throughout the day by applying pulses of heat at different times to Chrysanthemum seticuspe and Chrysanthemum morifolium under different regimens of light and dark. One experiment examined the elevation of heat sensitivity under different photoperiods in order to determine whether the transition from light to dark or vice versa serves as a signal for a clock-like regulation of heat sensitivity. Maximum heat sensitivity was frequently observed at a constant interval after light-off, but not after light-on, identifying the transition to darkness as the signal that initiates the elevation mechanism. We also examined the descending phase of heat sensitivity. Heat sensitivity peaked approximately 16 h after light-off and then gradually declined under dark conditions, suggesting an endogenous clock-controlled fluctuation. We further studied the effect of light on elevated sensitivity by conducting trials with dark periods of 13 or 16 h. Sensitivity peaked at both 10–13 and 13–16 h after light-off under the 16 h-dark condition, but only at 10–13 h after light-off under the 13 h-dark condition, indicating a rapid decline in heat sensitivity induced by light supplied 13 h after light-off. Results of the three experiments suggest that the daily elevation in heat sensitivity is potentially controlled by an internal clock that is reset by a transition from light to dark. A subsequent transition to light appears to eliminate elevated sensitivity. From this, we conclude that heat sensitivity is maximized toward the end of the night, irrespective of photoperiod, in chrysanthemums.

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  • Akihiro Hosomi
    Type: Original Articles
    Article ID: UTD-164
    Published: 2020
    [Advance publication] Released: June 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    This study aimed to determine the optimal shoot vigor to produce large fruit and high yields of the fig (Ficus carica L.) cultivars ‘Masui Dauphine’ and ‘Houraishi’. Fruit production of the two cultivars was compared for seven years on shoots of various vigor induced by different plant densities: 20, 61, 400, 667, and 2000 trees per 1000 m2, and all shoots occupied equal-sized basal areas (0.5 m2 for each shoot). Individual shoot weight (shoot weight) and number of superfluous shoots were greater in the trees grown at higher plant density. The greater shoot growth under higher plant density was consistent for seven years for ‘Masui Dauphine’, but such an increase was suppressed after the third year for ‘Houraishi’ trees. The relationship between fruit production and shoot weight showed that fruit maturation did not last until late autumn and the number of fruits harvested (fruit number) declined on the shoots smaller than approximately 0.15 kg on ‘Masui Dauphine’ trees and by approximately 0.8 kg in ‘Houraishi’ trees. In early autumn, however, the fruit number was larger on the smaller shoots than that on the larger shoots in ‘Houraishi’ trees. The annual means of individual fruit weight (fruit weight) were negatively correlated with shoot weight from the third to seventh years for ‘Houraishi’ trees, but only for the fifth year for ‘Masui Dauphine’ trees. The fruit yield per shoot (fruit yield) was positively correlated with shoot weight based on the fruit number. However, the correlation coefficients between fruit yield and shoot weight were lower in ‘Houraishi’ trees because the fruit weight was negatively correlated with the shoot weight. Relatively large shoots in a compact tree area will be useful for ‘Masui Dauphine’ figs to avoid fruit yield decline. Conversely, smaller shoots in a large tree area will be useful for ‘Houraishi’ figs to produce more and larger fruit in early season of harvesting.

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  • Yanqin Xu, Junjiang Zhou, Song Lu, Songtai Wang, Yin Zhou
    Type: Original Articles
    Article ID: UTD-176
    Published: 2020
    [Advance publication] Released: June 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Cymbidium is one of the largest orchid genera and it is famous for its ornamental, cultural, and economic value. Many Cymbidium species have an elegant flower fragrance, including C. faberi, C. goeringii, C. ensifolium, C. kanran, C. sinense, and so on. Although the components of the flower fragrance have been identified in many orchids, the molecular mechanism of their formation and regulation has not been explored. As one of the main components of flower fragrance, methyl jasmonate (MeJA) has been selected and the biosynthesis pathway was elucidated in some Cymbidium orchids. In order to modify the traits of flower fragrance in Cymbidium orchids, the underlying regulatory mechanisms need to be identified. In this study, four MYB transcription factors screened from RNA-seq results of C. faberi were successfully cloned and molecularly characterized. The activation of these CfMYBs with CfAOC and CfJMT promoters suggested that they may participate in the regulation of MeJA formation in C. faberi. This result could provide molecular support for the genetic modification and breeding of new C. faberi cultivars.

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  • Kazuya Maeda, Masahumi Johkan, Satoru Tsukagoshi, Toru Maruo
    Type: Original Articles
    Article ID: UTD-167
    Published: 2020
    [Advance publication] Released: May 26, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    In this study, we investigated the effect of salinity on photosynthesis and the distribution of photosynthates in the Japanese tomato (Solanum lycopersicum) cultivar ‘CF Momotaro York’ and the Dutch cultivar ‘Endeavour’. Although significant differences were not observed in fresh yield among the cultivars, there were significant differences between the control and salinity in terms of fresh yield, total soluble solids, and titratable acid. The total dry weight in the Japanese cultivar was not affected by salinity, but the Dutch cultivar had lower total weight under salinity compared to the control. Regarding dry mass partitioning, the Japanese cultivar had a lower dry mass ratio of vegetative organs and a higher ratio of fruits than the Dutch cultivar. Salinity did not affect the photosynthetic rate in the Japanese cultivar, but did affect the Dutch cultivar, possibly due to water use efficiency. These results indicate that this Japanese cultivar has characteristics of efficient fruit production under a low node-order pinching and high-density planting system, even under salinity conditions.

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  • Sota Koeda, Ryutaro Nakano, Takaya Sawaki, Kosuke Sato, Yoshiyuki Tana ...
    Type: Original Articles
    Article ID: UTD-184
    Published: 2020
    [Advance publication] Released: May 26, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    In Capsicum, loss of function mutation of acyltransferase (Pun1), putative aminotransferase (pAMT), putative ketoacyl-ACP reductase (CaKR1), and R2R3-MYB transcription factor (CaMYB31) have been reported to be the genetic causes of non-pungency. In the present study, 245 C. chinense accessions were initially screened for non-pungency attributes. Six candidates with identification numbers, No. 3327, No. 3356, No. 3529, No. 4026, No. 4028, and No. 4034 were selected by tasting test, and the non-pungency attribute was confirmed by high-performance liquid chromatographic analysis. Expression and sequence analysis inferred that the non-pungency of No. 3529 was due to the non-expression of Pun1. Analysis of pAMT confirmed that No. 3356 (pamt5) and No. 4034 (pamt9) had loss of function mutations. Because the non-pungency of No. 3327, No. 4026, and No. 4028 did not seem to be caused by mutation of either Pun1 or pAMT, the CaKR1 mutation was further examined using a polymerase chain reaction-based, co-dominant marker. Genotyping clarified that No. 3327, No. 4026, and No. 4028 had the same mutated CaKR1 allele as non-pungent No. 3341. Moreover, a crossing test with a pungent Habanero and No. 3341 clearly revealed that the non-pungency in No. 3327, No. 4026, and No. 4028 was a result of a loss of function mutation of CaKR1. Our previous and present studies have shown that non-pungent cultivars of C. chinense possessing pamt are widely distributed in Central America, South America and the West Indies (Caribbean), while non-pungent cultivars possessing Cakr1 originate from Bolivia and Peru. Some artificial selection may have occurred that was based on a preference for non-pungent peppers in the local region of origin.

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  • Yung-Chiung Chang, Tian-Cih Lin
    Type: Original Articles
    Article ID: UTD-120
    Published: 2020
    [Advance publication] Released: May 23, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    This study was conducted to investigate the effects of different temperature treatments on kumquat fruit development and qualities. Kumquat trees were placed in growth chambers at day/night temperatures of 36°C/28°C, 28°C/20°C, and then 20°C/12°C two weeks after the first physiological fruit drop. The results showed that there was a positive correlation between temperature and fruit drop. The total fruit drop rate increased with temperature. The group at 36°C/28°C had the highest total fruit drop rate of 63.7%. High temperature (36°C/28°C) suppressed kumquat fruit growth. With increases in temperature, the lengths and diameters of fruits decreased. Moreover, the kumquat peel color in the 36°C/28°C and 28°C/20°C groups did not change from green to orange. High day/night temperatures (36°C/28°C) during fruit growth stages suppressed fruit growth and could reduce fruit quality. Low day/night temperatures (20°C/12°C) prolonged the fruit development period, increasing fruit size and allowing peel color to change successfully. In order to avoid fruit drop caused by high temperatures at the fruit setting stage, pruning in early February is recommended.

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  • Mizuho Itoh, Chisato Goto, Yasunaga Iwasaki, Wataru Sugeno, Dong-Hyuk ...
    Type: Original Articles
    Article ID: UTD-143
    Published: 2020
    [Advance publication] Released: May 23, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    We investigated dry matter (DM) and fruit production of tomato plants, the effects of CO2 levels on DM production, and light-use efficiency (LUE) in a tomato production system based on short-term, low-truss crop management during six consecutive periods over one year in a commercial greenhouse. The CO2 concentration, total dry matter production (TDM), and LUE differed significantly among the periods. Since LUE was significantly correlated with the mean daytime CO2 concentration, we modeled LUE empirically from that. We developed a model to predict LUE and DM production of tomato plants and validated the model using data from the six periods. We accurately predicted LUE and TDM within a range of ca. 400 to 650 µmol·mol−1 daytime CO2 concentration. However, when daytime CO2 concentration was beyond this range, or when a management failure such as inadequate irrigation occurred, predicted values differed significantly from observed values.

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  • Ayako Nakamura-Yamaguchi, Nobutaka Kitahata, Chikako Nishitani, Norio ...
    Type: Original Articles
    Article ID: UTD-177
    Published: 2020
    [Advance publication] Released: May 23, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    In fruit production, fruit thinning is required to maximize fruit quality and to protect the mother trees. However, thinning is troublesome and laborious work. Fruit self-thinning is the spontaneous elimination of pollinated flowers or fruits within a week to a month after pollination. Since the fruit self-thinning trait has the potential to improve fruit trees, a number of studies using fruit crops such as apple, orange, and tomato have been conducted to clarify the underlying mechanisms. The Japanese pear accession ‘Chojuro’ and its descendants ‘Niitaka’, 162-29, and ‘Akiakari’ have this trait. To identify the pattern and trigger of thinning in the accessions, we pollinated all flowers on the flowering day and recorded the numbers of retained and abscised fruits and the order of flowering in the cluster. The number of retained flowers/fruits in a cluster was widely variable in ‘Chojuro’ and ‘Niitaka’, but was uniform at 3 to 6 fruits per cluster in 162-29 and ‘Akiakari’. In 162-29 and ‘Akiakari’, the earlier the flower opened, the more likely it was to be retained in the cluster, similar to previous observations in apple. In contrast, ‘Chojuro’ and ‘Niitaka’ fruits abscised independently of the flowering order. Therefore, the pattern of fruit self-thinning in pear depends on the accession. To identify the trigger for fruit self-thinning, we analyzed changes in the levels of endogenous auxins and abscisic acid. The results implicate auxin and, to a lesser extent, abscisic acid in fruit self-thinning. Retained fruits showed temperature-dependent transient auxin accumulation, which may trigger self-thinning in pear.

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  • Hasib Ahmad, Yoh-ichi Matsubara
    Type: Original Articles
    Article ID: UTD-165
    Published: 2020
    [Advance publication] Released: May 19, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    The present experiment was conducted to determine whether water extracts of lemon balm and oregano could suppress anthracnose in strawberry and to identify the important secondary metabolites responsible for such activity. Runner plants of three strawberry cultivars (Fragaria × ananassa Duch. ‘Sachinoka’, ‘Akihime’, and ‘Tochiotome’) were treated with water extracts (20%, w/v) of lemon balm (Melissa officinalis L.) and oregano (Origanum vulgare L.) separately and inoculated with Colletotrichum gloeosporioides (C. fructicola, CG1). Two weeks after CG1 inoculation, it was observed that the shoots and roots of the herb extract-treated plants had lower disease incidences and indices compared to those of the control regardless of the cultivar. Consequently, dry weights of the shoots of all the cultivars treated with the herb extracts were observed to be heavier than in the control; similarly, heavier dry weights of roots were also observed in herb extract-treated plants in ‘Sachinoka’ and ‘Tochiotome’. Upon analyzing the results of ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS), rosmarinic acid and luteolin in lemon balm and apigenin and protocatechuic acid in oregano were identified to be the metabolites with the highest concentration in their respective plants. In addition, the antifungal effect of all these compounds against CG1 was confirmed by in vitro tests. Thus, it can be concluded that water extracts of lemon balm and oregano could suppress anthracnose in strawberry plants, and the four identified compounds in the extracts could play key roles in the antifungal properties of these herbs.

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  • Yoshikuni Kitamura, Takashi Fudano, Yoko Kawanishi
    Type: Original Articles
    Article ID: UTD-179
    Published: 2020
    [Advance publication] Released: May 12, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Typically, hydrangea (Hydrangea spp.) plants produce flowers from early to mid-summer. However, their basal shoots often continue to produce flowers from late summer to autumn, and we call this unseasonal flowering. The flowering frequencies and flowering period durations of basal shoots were studied using 23 hydrangea cultivars and lines in 2017, 2018, and 2019. The flowering frequencies of basal shoots were relatively high in ‘Christmas’, ‘Endless Summer’, ‘Ezo’, ‘Rosea’, and ‘Sumida-no-hanabi’ in each year of the study. The flowering period durations of basal shoots ranged from one to six months among the cultivars and lines studied. Basal shoots of ‘Endless Summer’ and ‘Rosea’ continuously flowered during each year of the study period. The basal shoots of ‘Hatsushimo’, ‘Jyogasaki’, ‘Maihime’, ‘Masja’, ‘Ms. Hepburn’, ‘Uzu’, and No. 5 never flowered after August in any of the study years. Using ‘Masja’ and ‘Rosea’, axillary buds expected to develop into basal shoots were studied for flower bud initiation in November 2018. Flower bud initiation was observed in 8.9% and 77.4% of axillary buds of ‘Masja’ and ‘Rosea’, respectively. The number of nodes produced before flower bud initiation in the buds ranged from 10 to 12 and 8 to 13 in ‘Masja’ and ‘Rosea’, respectively. The numbers of nodes corresponded to those of the basal shoots that flowered up to August 2019 in both cultivars. The number of nodes produced by basal shoots of ‘Rosea’ that flowered after August 2019 ranged from 14 to 19, which was higher than those observed for the axillary buds expected to develop into basal shoots in November 2018. In conclusion, the flowering period duration of hydrangea basal shoots differs among cultivars. The floral initiations on the apical buds of the basal shoots after the previous autumn largely contribute to unseasonal flowering occurrences after August in hydrangea.

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  • Takeshi Saito, Yuya Mochizuki, Yasushi Kawasaki, Akio Ohyama, Tadahisa ...
    Type: Original Articles
    Article ID: UTD-171
    Published: 2020
    [Advance publication] Released: May 01, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    We aimed to monitor greenhouse tomato growth without destructive sampling and investigated an empirical growth model in which dry matter production was obtained as a product of light intercepted by plants and light-use efficiency. The intercepted light values were non-destructively determined on the basis of leaf width and length, and the number of leaves. Light-use efficiency was expressed as a function of daytime CO2 concentration. Three cultivation experiments were conducted with three tomato cultivars over two years. Significant regression lines and curves, as well as coefficients of the model, were obtained for each cultivar. Using photosynthetic curves of the three cultivars and solar radiation data, we suggest an approach to determine the recommended leaf area index to maximize dry matter production. The developed model has potential to improve yield and labor efficiency in tomato production.

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  • Mariko Kondo, Natsu Tanikawa, Takaaki Nishijima
    Type: Original Articles
    Article ID: UTD-174
    Published: 2020
    [Advance publication] Released: May 01, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    We investigated the molecular mechanisms underlying the pigmentation patterns of the dorsal petals in torenia (Torenia fournieri Lind. ex Fourn.) cultivars. ‘Piccolo Mix’ consists of lines exhibiting different pigmentation patterns in the limb of the dorsal petal, i.e., entirely pigmented (all-pigmented line), picotee with a pigmented margin (half-pigmented line), and entirely pale (pale line). In the all- and half-pigmented lines, expression of T. fournieri CYCLOIDEA2 (TfCYC2), which is involved in dorsal–ventral floral asymmetry, was inhibited by integration of Ty1/Copia-like LTR retrotransposon TORE2 into the exon of TfCYC2 (TfCYC2TORE2). The all-pigmented line was homozygotic for TfCYC2TORE2, while the pale line was homozygotic normal-type TfCYC2 (TfCYC2+). The half-pigmented line was heterozygotic TfCYC2TORE2/TfCYC2+. Therefore, the extent of pigmentation of the dorsal petal is negatively correlated with the gene dosage of TfCYC2+. Further, ‘Crown Violet’, another torenia cultivar exhibiting the same pigmentation pattern as the all-pigmented line of ‘Piccolo Mix’, was also homozygotic for TfCYC2TORE2. These results indicate that TfCYC2TORE2 is responsible for the marked enrichment of flower pigmentation patterns seen in torenia cultivars.

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  • Shizuyuki Tanaka, Masaki Iritani, Hajime Araki
    Type: Original Articles
    Article ID: UTD-155
    Published: 2020
    [Advance publication] Released: April 24, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    The combination effect of sowing and transplanting time on harvest time, yield, and external bulb quality was investigated to achieve earlier shipment of onions in northeastern Hokkaido, Japan. A total of five cultivars with different levels of photoperiodic responses for bulb formation were used in both the 1996/97 and 1997/98 trials. The seeds were sown on a monthly basis in a soil bed in an unheated plastic greenhouse from December to March, and the seedlings were transplanted outdoors from late April to mid-May. The daily minimum soil temperature was kept at almost 0°C, even when the air temperature in the plastic tunnel inside the greenhouse fell to −14.4°C in mid-winter. Seedling emergence took approximately 20 and 35 days in the 1996/97 and 1997/98 trials, respectively, when the seeds were sown in December and January. However, these seedlings grew slowly, and the leaf length, fresh leaf number, and leaf sheath diameter of the seedlings at transplanting time were all greater when the onion seeds were sown earlier. In addition, the bulb ripening time advanced with earlier transplanting. The cultivars, ‘Kitawase No. 3’ and ‘Kitahayate’, with an intermediate photoperiodic response, were harvested in early August if they were sown in December and January and transplanted from late April to early May. Moreover, with this combination of sowing and transplanting time, these cultivars produced an acceptable yield and bulb appearance in terms of marketable quality. The cultivar, ‘Sonic’, a typical short-day cultivar, had the earliest harvest time. However, the yield was very low due to the short period of leaf growth. On the other hand, for the cultivars ‘Okhotsk No. 1’ and ‘Kitamomiji 86’, which belong to a long-day photoperiodic response group, although the yields tended to increase under early sowing or early transplanting, they were not harvested by early August. On the basis of these observations, a new cropping type for early sowing and early transplanting will be adopted in northeastern Hokkaido by using the ‘Kitawase No. 3’ and ‘Kitahayate’ cultivars for early shipment in the domestic fresh onion market.

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  • Takashi Onozaki, Mamoru Satou, Mirai Azuma, Masato Kawabe, Kyoko Kawak ...
    Type: Original Articles
    Article ID: UTD-151
    Published: 2020
    [Advance publication] Released: April 23, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Fusarium root rot of lisianthus (Eustoma grandiflorum) caused by Fusarium solani is one of the most important and damaging lisianthus diseases. It occurs commonly in Japan and worldwide and causes serious crop losses. However, little effort has been made to breed lisianthus for resistance to this disease. We initiated a breeding program for resistance to F. solani in 2014. Twenty-nine lisianthus cultivars (E. grandiflorum) and one inbred line of Eustoma exaltatum were evaluated for resistance to two isolates (MAFF712388 and MAFF712411) of F. solani, as a first step toward the breeding of resistant cultivars. Seedlings were inoculated following injury by needle, then grown using hydroponic equipment—an efficient and reliable method for evaluating resistance. We found large differences in resistance among the 29 cultivars and the one inbred line tested. ‘Papillon Pink Flash’ was highly resistant to both isolates and showed no disease symptoms in a total of four tests. Furthermore, E. exaltatum Ohkawa No. 1 was highly resistant to isolate MAFF712388, showing no disease symptoms, and resistant to isolate MAFF712411. On the other hand, ‘Mink’, ‘Nagisa A’, ‘Nagisa B’, and ‘Vulcan Marine’ were stably susceptible with 70% to 100% of plants of these four cultivars wilting in all tests. MAFF712411 had greater pathogenicity than MAFF712388, but it is not clear whether the two isolates belong to different races.

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  • Fatema Tuz Zohra, Yuri Tominaga, Yomi Matsumoto, Naoko Taguchi, Ai Oku ...
    Type: Original Articles
    Article ID: UTD-163
    Published: 2020
    [Advance publication] Released: April 23, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Limonoids, a group of highly oxygenated triterpenoids mostly found in the Rutaceae and Meliaceae families, have many biological and physiological activities, such as anti-cancer, anti-microbial, and insecticidal ones. Recent studies suggest that some types of limonoids bind to a bile acid receptor, TGR5 (Takeda G protein–coupled receptor 5), and confer anti-obesity and anti-hyperglycemic effects. TGR5, also known as a G protein–coupled bile acid receptor 1 (GPBAR1), is a vital member of the membrane-bound G protein–coupled receptor (GPCR) family. In this study, we revealed the content of four types of limonoids (limonin, nomilin, obacunone, and limonin glucoside) and TGR5 ligand activity in a sour orange extract. The total concentration of the four limonoids was highest in the extract of ethyl acetate, followed by methanol and hexane in sour orange seeds. On the other hand, a luciferase assay using CHO cells transfected with a TGR5 confirmed that TGR5 ligand activity in the ethyl acetate extract of the seeds was as high as that in 50 μM nomilin, followed by that in the methanol extract of the seeds. The correlation coefficient between the limonoid content and the TGR5 ligand activity showed the highest value (r = 0.867) for nomilin, which supported a previous report that the TGR5 ligand activity of nomilin is higher than that of limonin or obacunone. However, the activity of the extract could not be explained by the nomilin content alone because the nomilin concentration in the extract used for the TGR5 assay was 3.9 μM, much lower than that in the control (50 μM nomilin), suggesting unknown compounds with higher TGR5 ligand activities in the seed extracts. In addition, the extract from cotyledons or germinated seeds showed higher TGR5 activity. Taken together, these results indicate that the seeds of citrus, such as the sour orange, may be a source of compounds that prevent obesity and metabolic disorders. In a future study, it will be necessary to comprehensively investigate citrus seed extracts to identify unidentified agonists for the TGR5 receptor.

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  • Takeshi Saito, Yasushi Kawasaki, Dong-Hyuku Ahn, Akio Ohyama, Tadahisa ...
    Type: Original Articles
    Article ID: UTD-170
    Published: 2020
    [Advance publication] Released: April 23, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    We validated a model for predicting dry matter (DM) production in growing plants without the need for destructive sampling with three tomato cultivars in a one-year experiment. In an attempt to improve DM, we managed the temperature and CO2 concentration in the greenhouse as well as the leaf area index (LAI) of the tomato plants 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. Although the model generally successfully predicted LAI in two of the cultivars, the observed LAI differed from the predicted value in the third cultivar. DM production, however, was predicted with high accuracy in all three cultivars from photosynthetically active radiation, temperature, CO2, and manual measurements of leaves; the predicted total DM in all cultivars at three sampling times fell within the range of observed DM ± standard deviation. By controlling temperature, daytime CO2, and LAI according to targets determined by simulations run on the model, we were able to improve yield to > 50 kg·m−2 per year. Therefore, the model was useful for improving tomato yield.

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  • Elly Kesumawati, Shoko Okabe, Munawar Khalil, Gian Alfan, Putra Bahagi ...
    Type: Original Articles
    Article ID: UTD-175
    Published: 2020
    [Advance publication] Released: April 23, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Begomoviruses, transmitted by whiteflies (Bemisia tabaci), have emerged as serious constraints to the cultivation of a wide variety of vegetable crops worldwide. Leaf samples from Solanaceae (tomato, tobacco, and eggplant) and Cucurbitaceae (cucumber and squash) plants exhibiting typical begomoviral yellowing and/or curling symptoms were collected in Northern Sumatra, Aceh province, Indonesia. Rolling circle amplification was conducted using DNA isolated from cucumber, squash, eggplant, and tobacco, and the full-length sequences of the begomoviruses were evaluated. The following viruses were isolated: bipartite begomoviruses Tomato leaf curl New Delhi virus (ToLCNDV), Squash leaf curl China virus (SLCCNV), Tomato yellow leaf curl Kanchanaburi virus (TYLCKaV), and a monopartite begomovirus Ageratum yellow vein virus (AYVV). Begomovirus diagnosis was conducted by PCR using begomovirus species-specific primers for Pepper yellow leaf curl Indonesia virus (PepYLCIV), Pepper yellow leaf curl Aceh virus (PepYLCAV), ToLCNDV, SLCCNV, TYLCKaV, and AYVV, which are the predominant begomoviruses. The primary begomovirus species for each plant were as follows: PepYLCAV for tomato, AYVV for tobacco, TYLCKaV for eggplant, ToLCNDV for cucumber, and SLCCNV for squash. This study provides valuable information for breeding begomovirus-resistant cultivars as horticultural crops.

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  • Young-Boon Lee, Wan-Soon Kim
    Type: Original Articles
    Article ID: UTD-138
    Published: 2020
    [Advance publication] Released: April 22, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    This study investigated the antifungal effect of chlorine dioxide (ClO2) dipping on Botrytis cinerea, the causal agent of gray mold, on cut rose flowers (Rosa hybrida L.). In vitro, the spore germination of gray mold was inhibited 100% by instant dipping with ClO2 solution (5 to 10 μL·L−1). In particular, ClO2 at 5 μL·L−1 was found to be ideal for hindering spore activity without causing any damage to the petals. This ClO2 antifungal effect on cut flowers was investigated in a white cultivar ‘Beast’ with different treatments: dipping (one second), spraying (4.8 mL), or gassing (two hours) with 5 μL·L−1 ClO2. Six days after ClO2 treatment, the incidence of gray mold in the artificially-inoculated flowers was 2.5% (dipping), 9.4% (spraying), or 8.4% (gassing), respectively, which were all significantly lower than the control incidence of 17.6%. Especially, ClO2 dipping reduced the incidence of gray mold by up to 26.1% compared to the control in five other rose cultivars (‘Antique Curl’, ‘Green Beauty’, ‘Feel Lip’, ‘Pink Heart’, and ‘Venus Berry’). No petal discoloration was detected, and petal color values (chroma or hue) were maintained regardless of ClO2 dipping. This result suggests that immediate ClO2 dipping is applicable to inhibit gray mold on cut rose flowers at a level of 5 μL·L−1 just before postharvest storage.

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  • Ryohei Fujita, Shigeki Jin, Takahiro Hayasaka, Kotaro Matoba, Yoichiro ...
    Type: Original Articles
    Article ID: UTD-139
    Published: 2020
    [Advance publication] Released: April 22, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Haskap (Lonicera caerulea subsp. edulis) is a deciduous shrub that produces blue-black edible berries with a sour-sweet taste. By expanding fruit color variation, the value of agricultural products is enhanced. Interspecific hybrids were obtained from crossings between Haskap and red-fruit bearing Miyama-uguisukagura (Lonicera gracilipes). The fruit color of the interspecific hybrids obtained was red-purple. Fruit color in Haskap is mainly affected by the concentration of anthocyanin. However, there are no reports on the chemical determinants of fruit color in interspecific hybrids between Haskap and Miyama-uguisukagura. We evaluated anthocyanin components in these hybrids and their parents using liquid chromatography/tandem mass spectrometry, and revealed the presence of five different kinds of anthocyanins. The major anthocyanin in interspecific hybrids and Haskap was cyanidin 3-glucoside, while in Miyama-uguisukagura, it was cyanidin 3,5-diglucoside. Some genotypes among interspecific hybrids showed higher concentrations of cyanidin 3,5-diglucoside and peonidin 3,5-diglucoside, compared with their parents. The genotypes of interspecific hybrids and the parents were evaluated by principal component analysis of anthocyanin concentration. Our study contributes to the identification of anthocyanin composition in fruits of interspecific hybrids and in expanding fruit color variation when breeding new varieties.

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  • Rafael A. Muchanga, Yoshitaka Uchida, Toshiyuki Hirata, Ryusuke Hatano ...
    Type: Original Articles
    Article ID: UTD-132
    Published: 2020
    [Advance publication] Released: April 21, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    The nitrogen (N) contribution of rye (Secale cereale L.) to tomato production may increase when grown and applied with hairy vetch (Vicia villosa R.) to the soil. To examine the uptake and recovery efficiency by tomatoes and retention in the soil of N derived from 15N-labeled rye applied as a monoculture and biculture with hairy vetch, a Wagner pot examination was conducted under plastic high tunnel conditions in Sapporo, Japan. Irrespective of cover crop residue management, the peak of rye-derived N uptake occurred between 4 and 8 weeks after transplanting (WAT) and ceased between 8 and 12 WAT. Rye-derived N uptake by tomatoes (shoot + fruit) was 58.3% greater in rye monoculture treatment than in the biculture of hairy vetch and rye treatment because of higher rye-derived N input, whereas rye-derived N recovery was greater in the biculture treatment (34.0%) than in monoculture treatment (26.9%). The soil retained 47.0% and 52.5% of the rye-derived N input in the biculture (972 mg N/pot) and rye monoculture (1943 mg N/pot) treatments, respectively. Rye-derived N stored in the roots and possibly lost was estimated at 19.0% and 20.6% of the rye-derived N input in the biculture and monoculture treatments, respectively. Hairy vetch in the biculture treatment contributed 46.2% more N to tomato production than rye, and the hairy vetch N contribution was more significant during the late period (4–8 WAT) than the early period (0–4 WAT) of tomato cultivation. Therefore, the biculture may change the N release pattern from both hairy vetch and rye, with the cover crops releasing high amounts of N in both the early and late periods of tomato cultivation. These results may help improve N management in vegetable production systems by maximizing the use of plant-derived N by crops, thereby reducing N fertilizer inputs.

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  • Mizuho Itoh, Chisato Goto, Yasunaga Iwasaki, Wataru Sugeno, Dong-Hyuk ...
    Type: Original Articles
    Article ID: UTD-148
    Published: 2020
    [Advance publication] Released: April 21, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    We investigated dry matter production and fruit characteristics of high-Brix tomatoes when plants were pinched above the third truss and electrical conductivity of the nutrient solution was gradually increased by changing the amounts of nutrients and NaCl. In the salinized treatment, fruit fresh weight was significantly decreased, and fruit Brix was significantly increased, relative to the non-salinized treatment. There were no significant differences in leaf area index, light use efficiency, light intercepted by leaves, total dry matter production, fruit dry weight, or dry matter distribution to fruit between treatments, but dry matter content of fruits was significantly increased in the salinized treatment. Therefore, dry matter production by plants was not reduced by the salinized treatment. The increase in fruit Brix was associated mainly with the increase in the dry matter content of fruits. Without reducing dry matter production, high-brix tomatoes can be produced by controlling the nutrient solution.

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  • Sutthinut Soonthornkalump, Shin-ichi Yamamoto, Upatham Meesawat
    Type: Original Articles
    Article ID: UTD-114
    Published: 2020
    [Advance publication] Released: April 15, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Paphiopedilum niveum (Rchb.f.) Stein, an endangered species, has been listed in CITES Appendix I and its germplasm conservation is required. To improve the regeneration of cryopreserved somatic embryos (SEs), adding 0.1 mM ascorbic acid (AsA) at a critical step during cryopreservation was investigated. The reactive oxygen species (ROS) and malondialdehyde (MDA) contents were also assessed during five steps (preconditioning, 1st preculture, 2nd preculture, osmoprotection, and dehydration) of a developed V cryo-plate technique as described briefly. Two-month-old SEs were preconditioned on modified Vacin and Went medium (MVW) containing 0.1 M sucrose for seven days. These SEs were precultured on MVW containing 0.2 M sucrose for one day (1st preculture) before being transferred to the same medium with 0.6 M sucrose for one day (2nd preculture). Precultured SEs were embedded on a cryo-plate, incubated in loading solution (LS) with 1.2 M sucrose for 30 min at 25°C and dehydrated with plant vitrification solution 2 (PVS2) for 60 min at 25°C. It was found that applying AsA on day 7 after culture (before the 1st preculture) could reduce total ROS and MDA levels, leading to a high regeneration percentage (39%) of cryopreserved P. niveum SEs.

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