The Horticulture Journal
Online ISSN : 2189-0110
Print ISSN : 2189-0102
ISSN-L : 2189-0102
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ORIGINAL ARTICLES
  • Shinya Kanzaki, Shiori Kamikawa, Asuka Ichihi, Yuta Tanaka, Kosuke Shi ...
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 435-443
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: August 22, 2019
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    The red coloration of the mango ‘Irwin’ skin is an important factor determining its value in the Japanese domestic luxury fruit market. In the present study, to investigate the molecular mechanism underlying anthocyanin biosynthesis of mango fruit skin, UFGT-like genes were isolated and the expression profile of anthocyanin-related genes was determined. Several UFGT-like genes were identified in transcriptome data of red ‘Irwin’ mango skin and two genes, MiUFGT1 and MiUFGT3, were considered to be involved in mango skin coloration. Deduced amino acid sequences of these genes exhibited high similarity to other plant UFGTs and contained the conserved PSPG box common to the glycosyltransferase family. The presence of a glutamine and a histidine residue at the C-terminus end of the PSPG box in MiUFGT1 and MiUFGT3, respectively, implied that MiUFGT1 and MiUFGT3 use glucose and galactose, respectively, as a sugar donor; however, the actual function and sugar donor preference of these enzymes remain to be elucidated. Expression analysis of anthocyanin-related genes during skin coloration suggested that MiCHS and MiANS, as well as MiUFGT1 and MiUFGT3, play important roles in the anthocyanin biosynthesis of mango fruit skin and that the expression of these genes is regulated by the MYB transcription factor, as reported in other plant species.

  • Lijuan Feng, Yanlei Yin, Xuemei Yang, Haixia Tang, Qiqing Jiao
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 444-454
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: September 03, 2019
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    Pomegranate (Punica granatum L.) is a functional fruit that is abundant in bioactive substances. Punicalagin is an abundant and important phenolic compound in pomegranate, but the variation patterns and linkage of punicalagin and related synthetic bioactive substances during development are unclear. In this study, the dynamic variations in punicalagin and related synthetic bioactive substances were investigated in different parts of pomegranate during development phases. Punicalagin and related synthetic substances in the pomegranate pericarp, juice, seeds, and leaves were determined by high-performance liquid chromatography. Results revealed that punicalagin, gallic acid, shikimic acid, and total phenol contents, as well as DPPH radical scavenging activity, decreased gradually in the fruit, whereas pentagalloylglucose and 3-dehydroshikimic acid contents increased gradually. Seven substances yielded different variation patterns in the leaves. Ellagic acid content initially decreased and then increased in the fruit and leaves. Pentagalloylglucose was mainly detected in the leaves, while shikimic acid, 3-dehydroshikimic acid, punicalagin, gallic acid, and ellagic acid were mainly found in the pericarp. The highest punicalagin concentration was 156.735 mg·g−1 in the TSH pericarp. Shikimic acid and 3-dehydroshikimic acid were closely related to gallic acid. Punicalagin was significantly positively correlated with gallic acid in the fruit, and significantly negatively correlated with pentagalloylglucose. Antioxidant activity and total phenol content were also closely correlated. Punicalagin and related substances presented different variation patterns in various pomegranate parts during development. Punicalagin was the most abundant phenolic compound in the pericarp, and this finding correlated significantly with gallic acid, ellagic acid, shikimic acid, 3-dehydroshikimic acid, and pentagalloylglucose in the fruit. The pomegranate pericarp contained abundant phenolic compounds and exhibited high antioxidant activity.

  • Masashi Yamamoto, Makoto Takeuchi, Kenji Nashima, Toshiya Yamamoto
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 455-461
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: September 12, 2019
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    Chromosome analysis of pineapple (Ananas comosus (L.) Merr.), one of the most important tropical fruit trees, was conducted. All experiments were carried out using root tips derived from three cross combinations as plant materials. Good preparations, with all 50 chromosomes relatively extended and well-spread without cytoplasm, were observed under enzyme conditions of “2% Cellulase Onozuka RS and 0.5% Pectolyase Y-23” without pretreatment with 2 mM 8-hydroxyquinoline. CMA-positive (+) bands were observed in telomeric positions of two chromosomes. DAPI-negative bands (−) corresponded with CMA+ bands. The numbers and positions of CMA+ bands were stable. Fluorescence in situ hybridization of rDNA was performed. The 18S-5.8S-25S rDNA sites were detected in telomeric positions of two chromosomes. The 5S rDNA sites were also detected in telomeric positions of two chromosomes. The 5S and 18S-5.8S-25S rDNA sites were located on different chromosomes. The 18S-5.8S-25S rDNA sites corresponded with the CMA+/DAPI− bands. The numbers and positions of rDNA sites were stable.

  • Etsuko Itabashi, Daniel J. Shea, Nobuko Fukino, Ryo Fujimoto, Keiichi ...
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 462-470
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: July 24, 2019
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    Vernalization, a floral transition stimulated by the prolonged exposure to cold temperatures, is an undesirable feature in the breeding of leafy vegetables that impairs productivity by promoting bolting. Cabbage is categorized as a green plant vernalization type; only older plants possess vernalization competence. Despite being of agricultural importance in the breeding of bolting resistance, the molecular mechanism of age-dependent acquisition of vernalization competence is poorly understood. In Arabidopsis, FLOWERING LOCUS C (FLC) is a key vernalization response gene that functions as a floral repressor. Its expression decreases upon cold exposure, leading to floral induction. In this study, we characterized three FLC orthologs in cabbage (BoFLC1, BoFLC2, and BoFLC3). Predicted amino acid sequences of the three BoFLC cDNAs were highly conserved with the MADS-box domain. The overexpression of the three BoFLCs in Arabidopsis displayed late flowering phenotypes, indicating the functional conservation of these paralogs as floral repressors in cabbage. The expression analyses before and after constant cold treatment given at different plant ages showed that the three BoFLCs displayed distinct responses to prolonged cold exposure. Regardless of plant age, BoFLC1 declined less markedly, whereas BoFLC2 and BoFLC3 were repressed by sufficient long cold treatment. In both younger and older plants, the expression of the ortholog of floral integrator gene, FLOWERING LOCUS T (FT), was induced by cold treatment, probably due to a reduction in the repressive effect of BoFLCs, suggesting that the fate of age-dependent vernalization is determined independently or downstream of BoFT induction. Our results provide new insights into the mechanism of green plant vernalization in Brassica vegetables.

  • Nakao Kubo, Hayato Ueoka, Shigeru Satoh
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 471-480
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: July 10, 2019
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    In Japan, many turnip (Brassica rapa) cultivars are known as heirloom vegetables, especially in Shiga Prefecture, which is close to the old capital of Japan, Kyoto. Of these, ‘Omikabu’, an heirloom white turnip cultivar in Shiga Prefecture is referred to as the ancestor of the white turnip cultivars, ‘Shogoinkabu’, ‘Tennojikabu’, and ‘Yoriikabu’. Many “red turnip” cultivars that are red or purple-skinned varieties (and sometimes with colored flesh and petioles), also grow in Shiga Prefecture, and are mainly processed into pickled vegetables. However, their origins have not yet been fully verified. In this study, construction of neighbor-joining phylograms and population structure analyses were performed based on eight simple sequence repeat markers for white and red turnips, plus two non-turnip B. rapa vegetables (Chinese cabbage and mizuna). For the white turnip-related lines, a claim that ‘Shogoinkabu’, ‘Tennojikabu’, and ‘Yoriikabu’ are derived from ‘Omikabu’ could not be supported in this study because ‘Omikabu’ lines were separated from the above three cultivars in the phylogram. In contrast, an ‘Omikabu’ line, ‘Omikabura RU’, formed a cluster with ‘Jonansensuji mizuna’, suggesting a genetic relationship (a crossing in the past) between them. For red turnips, close placements of ‘Kisobenikabu’-‘Shinshukabu’, ‘Hinona’-‘Kitanoshokabu’, and ‘Biwakobenikabu’-‘Yurugikabu’ were found in the phylogram, each of which was in good agreement with the proposed cultivar’s origin. The data in this study provide useful information for understanding the genetic relationships among Japanese heirloom turnip cultivars.

  • Rihito Takisawa, Sota Koeda, Tetsuya Nakazaki
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 481-487
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: July 23, 2019
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    In pat-2 parthenocarpic tomatoes (Solanum lycopersicum L.), inhibition of seed production prevents their breeding and development. Low seed set is thought to be caused by a pleiotropic effect of the pat-2 gene because the number of seeds from pat-2 parthenocarpic tomato cultivars is generally low; however, research on the relationship between low seed set and the pat-2 gene is lacking. In this study, to clarify the effect of the pat-2 gene on seed production and develop a method for promoting seed production in pat-2 parthenocarpic tomatoes, we examined the relationship between the pat-2 gene and low seed set and the effect of aminoethoxyvinylglycine (AVG), an indole-3-acetic acid (IAA) biosynthesis inhibitor, on seed production in ‘Renaissance’, a pat-2 parthenocarpic tomato cultivar. In an F2 population derived from a cross between ‘Micro-Tom’ and ‘Renaissance’, the number of seeds in plants homozygous for the pat-2 allele was significantly lower than that in heterozygous plants and that homozygous for the Pat-2 allele. This indicated that low seed set was genetically associated with the pat-2 allele, and that low seed set was unavoidable when using the pat-2 gene for breeding of parthenocarpic tomato cultivars. Therefore, it is important to develop a method to promote seed production in pat-2 parthenocarpic tomatoes. In this study, we examined the effect of AVG on seed production in ‘Renaissance’. We found that treatment with 30 μM AVG significantly increased the number of seeds in ‘Renaissance’. In addition, when we treated flower clusters with AVG solution at the first flower anthesis, the effect of treatment with 30 μM AVG on increasing seed set was highest for the flower in the second position in a cluster, which suggests the effect of AVG on promoting seed production changed depending on the stage and/or position. Our results showed that low seed set was genetically associated with the pat-2 allele and that AVG is an effective tool to promote seed production in pat-2 parthenocarpic tomatoes. Based on these results, research progress on improving seed production in parthenocarpic tomatoes with the pat-2 gene is expected to accelerate in the future.

  • Abdelsattar Abdelkhalik, Nuria Pascual-Seva, Inmaculada Nájera, Miguel ...
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 488-498
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: August 20, 2019
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    Water is an essential resource for food production, and agriculture consumes close to 69% of total freshwater use. Water shortage is becoming critical in arid and semiarid areas worldwide; therefore, it is vital to use water efficiently. The objective of this research was to evaluate the response of onion growth, plant water status, bulb yield, irrigation water use efficiency and bulb quality using three continued deficit strategies, applying 100, 75, and 50% of the irrigation water requirements during three seasons. The yield response factor was 0.71, indicating that in the analysed conditions the crop was tolerant to a water deficit. Compared to full irrigation, deficit irrigation with 75% of the irrigation water requirements resulted in a low yield and profit reduction for the growers (10.3% and 10.9%, respectively), but also important water savings (26.6%), improving both the irrigation water use efficiency and water use efficiency. However, onion exposure to severe water deficits at 50% of the irrigation water requirements drastically reduced plant growth and bulb yield and growers’ profits, although it did increase their soluble solid content. Irrigating at 75% of the irrigation water requirements could be an actionable strategy for onion production under water-limited conditions.

  • Kwankhao Cha-um, Sirikorn Sangjun, Kunyapon Prawetchayodom, Cattarin T ...
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 499-506
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: June 26, 2019
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    Plants produce a variety of crystals with different shapes and sizes. Based on their appearance, calcium oxalate crystals, especially raphides, have been suggested to play a key role in the defense mechanism against insect attack and microbial infections. Colocasia esculenta, a tropical plant primarily grown for its edible corms contains a large number of cells (idioblasts) with needle-like crystals of calcium oxalate (i.e., raphides). The concentration of raphides in the plant varies with the ploidy level, cultivar, organ, and micro environment. The objective of this study was to evaluate the physiological, organic and inorganic biochemical changes in the differentiated leaves of elephant ear (Colocasia esculenta var. aquatilis) and examine the rate of release of these compounds in water soluble forms. Regarding photosynthetic functions, the net photosynthetic rate (Pn) was positively related to light intensity, especially in fully expanded and old leaves. However, the Pn, transpiration rate (E), and stomatal conductance (gs) in young leaves were lower than those in fully expanded and older leaves, resulting in low levels of total soluble sugar content in both the petioles and leaf blades of young leaves. In contrast, oxalic acid and calcium in both petioles and leaf blades peaked at > 2.0 mg·g−1 FW and ~185 mg·g−1 FW, respectively. A large number of idioblasts (~5.5 idioblasts per observed microscopic field) were observed in young leaves. Oxalic acid and calcium ions extracted from the leaf tissues were rapidly dissolved in hot water (85°C) for 10–15 min, leading to a decline in the number of idioblasts. Based on these results, petioles and leaf organs of elephant ear may be eaten safely after boiling in hot water for 15 min to dissolve CaOx.

  • Koji Tanase, Yosuke Matsushita, Tomofumi Mochizuki
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 507-513
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: July 13, 2019
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    Virus-induced gene silencing (VIGS) systems are widely used to downregulate target host genes in plants. The Cucumber mosaic virus (CMV), which has a broad host range, has been used as a VIGS vector system in research. In this study, a VIGS vector system derived from the pepo strain of CMV (CMV pepo) was tested for its use in functional analysis of a target gene in Petunia. The CMV pepo caused systemic infections without severe viral symptoms in petunia plants. A vector containing a short fragment (57 bp) of the chalcone synthase gene (PhCHS-A) was constructed (PhCHSA-CMVpepo) and petunia plants were mechanically inoculated with it. Corollas were white in plants infected with PhCHSA-CMVpepo, but were purple (original color) in plants infected with wild-type CMV pepo. In white corollas, the mRNA level of PhCHS-A was downregulated compared to that in purple corollas. These results indicate that the CMV pepo vector system is useful for VIGS research in flowers of the genera Petunia.

  • Kimitoshi Sakaguchi, Chisato Isobe, Kazuyoshi Fujita, Yoshihiro Ozeki, ...
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 514-520
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: July 17, 2019
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    Modern molecular biology techniques have enabled the generation of novel flower colors. Standard cultivated varieties of delphinium have blue flowers as a result of the biosynthesis and accumulation of delphinidin-based anthocyanins. Some cultivars have pink flowers due to the biosynthesis and accumulation of pelargonidin-based anthocyanins. The biosynthetic pathway of the latter becomes active due to the inactivation of flavonoid 3',5'-hydroxylase. Cyanidin-based red-purple flowers have not been identified to date in delphiniums because these species do not express the flavonoid 3'-hydroxylase gene. However, in our previous work, we identified expression of the flavonoid 3'-hydroxylase gene in a wild delphinium (Delphinium zalil) that accumulates quercetin 3-glycoside. D. zalil lacks the anthocyanidin synthase, the key enzyme to produce anthocyanins, so the flowers do not contain any anthocyanins. Here, we report the use of conventional breeding to introduce cyanidin biosynthesis into delphiniums. We introduced the flavonoid 3'-hydroxylase gene of D. zalil into D. cardinale by hybridization breeding, causing accumulation of cyanidin-based anthocyanin. In the hybrid plants, flavonoid 3'-hydroxylase was transcribed and a cyanidin-based anthocyanin was biosynthesized, generating novel purple-red flowers. Greater understanding of the anthocyanin biosynthetic genes expressed in wild species will benefit the development of breeding strategies to generate novel flower colors in cultivars of high horticultural value.

  • Takashi Onozaki, Mirai Azuma
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 521-534
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: August 31, 2019
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    Flower vase life is one of the most important traits for ornamental plants. The vase life of cut dahlia (Dahlia variabilis) flowers is very short, and genetic improvement of this trait is desirable. We started a breeding research program in 2014 to improve the vase life of dahlia flowers using conventional cross-breeding techniques. We found large significant differences in flower vase life among 24 dahlia cultivars: Nine cultivars had long vase life (e.g., ‘Syukuhai’, ‘Rinka’, and ‘Micchan’); eight had normal vase life (e.g., ‘Kamakura’, ‘Agitate’, and ‘Benifusya’); and seven had short vase life (e.g., ‘Gin-Ei’, ‘Port Light Pair Beauty’, and ‘Yumesuiren’). We used 22 cultivars as initial breeding materials, repeatedly crossed them, and selected promising offspring with long vase life for three generations from 2014 to 2018. Two cycles of selection and crossing led to a 1.7-day increase in vase life (population mean) from the first to the third generation, clearly showing that this approach can extend the vase life of dahlia flowers. The mean vase life of ‘Kamakura’, a leading white dahlia cultivar in Japan, was 5.0–6.2 days in distilled water, 6.0–6.8 days in an isothiazolinic antibacterial agent CMIT/MIT solution (5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one) and 6.0–7.6 days in a GLA solution (10 g·L−1 glucose, 0.5 ml·L−1 CMIT/MIT, and 50 mg·L−1 aluminum sulfate), whereas in six finally selected lines it was 6.2–12.0 days in distilled water, 6.6–10.2 days in CMIT/MIT solution, and 9.4–13.6 days in GLA solution (1.4–2.1 times that in ‘Kamakura’). In particular, the selected second-generation line 606-46 showed a stably longer vase life than ‘Kamakura’. ‘Micchan’, which has a long vase life, was a common progenitor used for breeding of parental lines in cross combinations with long vase life in the second generation and all cross combinations in the third generation. The final six selected lines with long vase life were all progeny of ‘Micchan’. Our results strongly suggest that ‘Micchan’ has genes related to long flower vase life, and that the trait is heritable.

  • Kenji Ureshino, Hiroya Takara, Ikuo Miyajima
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 535-540
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: September 12, 2019
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    Intersubgeneric crosses between white-flowered evergreen azalea species and a yellow-flowered deciduous azalea (Rhododendron japonicum f. flavum) can produce yellow-flowered evergreen azaleas. The petal color of F1 progenies from these crosses is known to fade during petal development due to a high expression of the carotenoid cleavage dioxygenase 4 (CCD4) gene inherited from the evergreen species. In this study, to facilitate the selection of evergreen azalea species as cross parents that have low expression levels of CCD4 in developing petals, CCD4 expression levels were compared among 16 evergreen azalea species belonging to the subgenus Tsutsusi. The identity values of the deduced amino acid sequences of CCD4 were high (from 97% to 100%) among evergreen azalea species. The expression levels of CCD4 genes in petals of evergreen azalea species at the day of anthesis varied widely from 2.04 to 20.47 times relative to that in R. japonicum f. flavum. Among these species, R. amanoi maintained low CCD4 expression levels throughout all petal development stages that were not significantly different from those of R. japonicum f. flavum (JPN). This species is therefore considered a promising breeding material for producing yellow-flowered evergreen azaleas.

  • Samak Kaewsuksaeng, Masahiro Nomura, Masayoshi Shigyo, Naoki Yamauchi
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 541-547
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: June 19, 2019
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    Hot water treatment (HWT) was applied to a new Thai lime cultivar fruit, ‘Pichit 1’ (Citrus aurantifolia Swingle) to investigate its effect on chlorophyll (Chl) degradation and postharvest quality during storage. Fruit were treated with HWT with temperatures of 45, 48 or 50°C for 3, 5, and 10 min and then kept in the dark at 25°C and 90 ± 5% RH. Lime peels retained a greener color after HWT at 48°C for 5 min compared to the fruit given any other treatment. HWT at 48°C for 5 min efficiently delayed the decrease in the hue angle value acquired during storage. Chlorophyllide a, pheophorbide a, pyropheophorbide a, 132-hydroxychlorophyll a, pheophytin a, and an unknown catabolite, which may be a chlorophyllide a derivative, were detected as Chl derivatives in the fresh limes. The levels of chlorophyllide a, pheophytin a, and 132-hydroxychlorophyll a gradually decreased during the progression of peel degreening. Those derivative levels were higher in the fruit treated with HWT than the control. Moreover, the organic acid content was maintained at higher levels in the fruit treated with HWT than the control during storage at 25°C. During storage, the sugar content was seen to decrease with or without HWT; however, sugar reduction in the control was more rapid. It appeared that HWT reduced the degradation of Chl by controlling its catabolites. Therefore, HWT affected the fruit quality of green ‘Pichit 1’ limes in storage.

  • Atsushi Ikegaya, Tomoyasu Toyoizumi, Seiji Ohba, Teruko Nakajima, Akih ...
    Type: Original Articles
    2019 Volume 88 Issue 4 Pages 548-558
    Published: 2019
    Released: October 26, 2019
    [Advance publication] Released: September 12, 2019
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    The objective of this study was to clarify the effects on quality when exporting small amounts of fresh fruits and vegetables by mixed loading. When exporting small amounts of multiple varieties of fruits and vegetables, it is essential to reduce transport costs by using reefer containers for mixed cargo. A lot of research has been conducted on the distribution and storage technology of fruits and vegetables. However, conditions and techniques have primarily been examined only for single items, and research on transporting mixed cargo has not been done. In this study, we used a new reefer container with only marginal internal temperature variability (set to 0°C), and exported fruits and vegetables by sea as a mixed cargo. Subsequently, the fruits and vegetables exported by sea were compared by sensory evaluation with those exported by air. Satsuma mandarins, onions, salad onions, Welsh onion leaf blades, and lettuces were almost the same quality when shipped by sea as by air without any specific treatment. Other items such as tatsois and Welsh onion stems required film, plastic bags, and other packaging to reduce fresh weight loss when exporting by sea. These results suggest that fruits and vegetables can be exported by sea with similar quality to that by air. However, it is necessary to consider the storage temperature, packaging material and conditions, and item selection.

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