The Horticulture Journal
Online ISSN : 2189-0110
Print ISSN : 2189-0102
Volume 87 , Issue 2
Showing 1-18 articles out of 18 articles from the selected issue
ORIGINAL ARTICLES
  • Kaori Matsuoka, Naoki Moritsuka, Shinnosuke Kusaba, Kiyoshi Hiraoka
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 155-165
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: September 14, 2017
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    In blueberry culture, sulfur is applied to enhance soil acidification, and fertilizer is applied to increase growth and yield. We investigated the effects of soil management on the solubilization of 13 elements in the root zone and their relationships with absorption by blueberry bushes. In a 2-year pot experiment, four-year-old rabbiteye blueberries ‘Onslow’ were grown in one of three soils (an Andosol, a Cambisol, or a Fluvisol), with or without soil treatment (no treatment, acidification, fertilization, or acidification plus fertilization). The soil solution was collected eight times during the experiment. Fruit, leaves, branches, stems, and roots were sampled during and at the end of the experiment. The concentrations of 13 elements (N, Na, Mg, Al, P, K, Ca, Mn, Fe, Cu, Zn, Rb, and Cs) in the samples were analyzed. Soil solution pH was also measured. In all soils, the soil solution pH was decreased to 3.7–4.3 by acidification and also to 4.5–6.1 by fertilization. Acidification tended to increase the average concentrations of Al (77–1421 fold), Zn (18–414 fold), and Fe (1.2–204 fold) in the soil solution, whereas fertilization tended to increase the average concentrations of NH4+ (33–205 fold), Cs (3.0–9.9 fold), and NO3 (2.1–8.4 fold). The acidification plus fertilization further increased the concentrations of these elements in the soil solution except for Fe. On the other hand, the concentrations of Na, P, Fe, and Cu in the soil solution were influenced by the soil type and were not changed by any soil treatments in a particular soil. Across all soil types and treatments, the average concentrations of N, P, K, Mn, Cu, and Zn in the soil solution were significantly correlated with the content of the corresponding element in the blueberry bushes. For these elements, nondestructive sampling and analyses of soil solution in the root zone can be effective as a real-time soil test. The content of seven other elements (Na, Mg, Al, Ca, Fe, Rb, and Cs) in the bushes did not reflect the soil solution concentrations partly due to the lower requirement than their supply from the soil.

  • YoSup Park, ByulHaNa Lee, Hee-Seung Park
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 166-173
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: October 14, 2017
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    This study was conducted to understand the characteristics of winter chill accumulation in South Korea and to predict its fluctuations due to global climate change. Using climate data for 30 regions and previously established models, we estimated winter chill accumulation for those regions and predicted future changes. The temperature range from 0–7.2°C is considered effective for breaking endodormancy, so an average of 1750 chilling hours was supplied per winter between 1999 and 2015. The 30 study regions were divided into five groups based on temperature distribution. Groups 1 and 2 had fewer and more than 830 annual hours at temperatures of 0–3.6°C, respectively. Groups 3, 4, and 5 had 950–1310, 1310–1515, and more than 1515 hours, respectively, at temperatures below 0°C. The number of hours the groups was exposed to the effective temperature range for breaking endodormancy under the projected elevated temperature conditions decreased from group 5 to group 1; the loss of effective hours was in the same order. As a result, winter chill accumulation abruptly decreased from group 5 to group 1 under elevated climatic temperature conditions. The delay in the start of winter chill accumulation increased from groups 4 and 5 to group 1, and the end came earlier in the same order; groups 4 and 5 showed very similar changes at the start and end of chill accumulation. Under elevated temperature conditions, chilling accumulation is expected to start later and end earlier in all regions. These changes will be accelerated with a greater rise in regional temperatures, and elevated temperatures will lengthen the endodormancy of woody plants, but shorten the period of chilling accumulation. The results of this study can be used as fundamental data to establish plans for responses to climate change such as the selection and renewal of cultivars.

  • Kazuhiro Matsumoto, Toru Kobayashi, Tomoaki Kougo, Tomomichi Fujita, S ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 174-183
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: November 08, 2017
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    ‘Kurenainoyume’ is a new red-fleshed apple cultivar with a gradually increasing cultivation area. However, cork spot-like physiological disorder (CSPD) of the apple skin has become a serious problem over the years. Therefore, the development of strategies to reduce and prevent CSPD is strongly desired by farmers. To this end, we investigated the effectiveness of i) spraying calcium (Ca), boron (B), or both on the tree and ii) pre-harvest fruit bagging. Ca or B solutions or both did not decrease CSPD incidence. Furthermore, no relationship was detected between CSPD and the Ca/B content of fruit and leaves, demonstrating that the occurrence of CSPD might not be due to a deficiency in these elements. Pre-harvest fruit bagging reduced the development of CSPD depending on the light permeability of the paper bags used. Moreover, CSPD development was positively correlated with sunshine duration. Therefore, to prevent CSPD, fruit should be covered with light-impermeable paper bags at least from mid-July to late-September because the fruit covered for a shorter period developed CSPD. Thus, we propose that pre-harvest fruit bagging with light impermeable paper could be a useful and practical strategy to reduce or prevent CSPD in ‘Kurenainoyume’.

  • Ziaurrahman Hejazi, Shuji Ishimura, Chitose Honsho, Takuya Tetsumura
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 184-192
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: November 08, 2017
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    A practical dwarfing rootstock for the persimmon (Diospyros kaki Thunb.), ‘MKR1’, is normally propagated by cuttings collected from root suckers. However, optimal conditions for propagating leaf-bud cuttings from this variety have not been researched. Thus, several methods influencing survival, rooting and root system structure were investigated in the present study. Cuttings planted in late June survived and rooted better than those planted in late July and August, and the rooted cuttings planted in late June also survived winter better. The two different irrigation methods, either a mist system, or a tray with a polyethylene tent (tray-polyethylene-tent, or TPT) did not significantly affect survival and rooting. However, the primary root length was longer in the TPT and the root dry weight was heavier under the mist system. Although the rooting medium did not significantly affect the survival of cuttings, the rooting percentage of cuttings planted in perlite was the lowest. The cuttings planted in peat in late June and placed under the mist system had adventitious root initials 17 days after planting and adventitious roots were observed on the cuttings by 22 days after planting. A quadratic regression curve predicted that the highest rooting percentage would result from treatment of ‘MKR1’ cuttings with approximately 2000 mg·L−1 indole-3-butyric acid (IBA), while a different curve predicted that the lowest root number would result from treatment with approximately 1000 mg·L−1 IBA. Interestingly, more than 50% of the cuttings treated with a quick dip in 0 mg·L−1 IBA successfully rooted. Although the treatment with a higher IBA concentration resulted in greater root system development on the rooted cuttings, treatment with very high IBA concentrations such as 4000 or 5000 mg·L−1 caused fading of leaves and dieback of cuttings.

  • Tatsuo Sato, Harufumi Saito, Keisuke Maejima, Keiko Kuba, Ani Widiastu ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 193-199
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: September 08, 2017
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    This study aimed to investigate the preventive effect of periodic hot water spraying against powdery mildew in strawberry as an alternative to chemical application as a protection method. Young upper leaves of ‘Sachinoka’ were dipped in hot water at 50°C for 20 s. Conidia of powdery mildew were inoculated 24 h after the treatment. The occurrence and growth rates of powdery mildew were apparently lower on leaves dipped in hot water than on those left untreated. Thus, resistance against powdery mildew was thought to be successfully induced by heat shock. Change in leaf temperature was tested using a prototype of a hot water sprayer at 57 ± 2°C. The resultant rise in temperature and temperature attained varied widely across the leaves. Nonetheless, the minimum requirement of a leaf temperature of 50°C in 10 s for inducing systemic resistance against crown rot could be attained in the treated plants. In this study, weekly hot water spraying treatments were conducted in ‘Sachinoka’ in 2008 and in ‘Tochiotome’ and ‘Hitachi-hime’ in 2009. In 2008, powdery mildew occurred explosively in the non-treated plants. However, its occurrence in plants treated with hot water spraying was less than that in the controls, but more than that after chemical application. In 2009, the occurrence rate was lower than that in the non-treated group of 2008 and extremely low after hot water spray treatment and chemical protection in both the varieties. Whether the difference in the occurrence of powdery mildew in both the years was because of the difference in environmental conditions or the difference between the varieties is not known. The plant height of ‘Hitachi-hime’ tended to become short after hot water spraying; however, no serious effects were noted on the growth and yield of strawberry plants. In conclusion, heat shock treatment by using hot water spraying can be considered an alternative method to chemical protection against mild powdery mildew incidence in strawberry.

  • Yoko Takeuchi, Emika Kakizoe, Ryosuke Yoritomi, Miyuki Iwato, Akira Ka ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 200-205
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: September 07, 2017
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    We investigated the resistance to stem blight disease (Phomopsis asparagi (Sacc.)) in the progeny of two combinations of interspecific crosses between Asparagus officinalis (sensitive) and Asparagus A. kiusianus (resistant) in an effort to produce resistant cultivars. The progeny showed different degrees of disease severity, depending on the combination of crosses. Most of the hybrids derived from AO0060 (A. officinalis) × AK0501 (A. kiusianus) showed high disease resistance comparable to that of A. kiusianus. The results indicate that disease resistance could be introduced from A. kiusianus into A. officinalis, and that the selection of an appropriate cross combination is important for the production of disease-resistant cultivars. We analyzed the parents and hybrids of reciprocal crosses between A. officinalis and A. kiusianus using derived cleaved amplified polymorphic sequence markers to investigate the inheritance of the chloroplast genome, whose inheritance and genetic characteristics are not yet known. The chloroplast DNAs were inherited from the maternal parent, indicating that no major genes related to stem blight resistance were found in the chloroplast DNA.

  • Hiroki Ueno, Takeshi Maeda, Naoki Katsuyama, Yu Katou, Satoshi Matsuo, ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 206-213
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: October 11, 2017
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    Several Japanese tomato cultivars develop a physiological disorder called leaf marginal necrosis, which occurs in relatively young compound leaves. Although the positions of the observed symptoms differ from those caused by inadequate potassium (K+) supplementation, previous studies have reported a relationship between the reduction of K+ content and the occurrence of this disorder. However, the mechanism of the relationship between K+ deficiency and leaf marginal necrosis remains unstudied. In the present study, the relationship between K+ deficiency in leaflets and leaf marginal necrosis was investigated by cation measurement and gene expression analysis to understand the possible mechanism responsible for the induction of leaf marginal necrosis. First, cation measurement of the two cultivars differing in their symptom intensities showed a trend of K+ reduction in the ‘CF Momotaro J’ cultivar developing leaf marginal necrosis at the tip leaflets positioned under the flowering fruit truss. Next, a comparison between the basal and tip region of the leaflet from four cultivars differing in their symptom intensities revealed that the K+ concentration in tip leaflets was significantly lower in the tip regions compared to the basal region, especially in the two cultivars ‘CF Momotaro J’ and ‘Momotaro grande’, leading to leaf marginal necrosis. The gene expression analysis of the basal and tip regions identified that the expression patterns of jasmonate-related genes were upregulated in the tomato leaflets with low K+ concentration. The gene expression of a leaf senescence marker gene, a homologue of the SAG12 gene of Arabidopsis thaliana, was detected only in the leaf tip region samples with the lowest K+ concentration. Furthermore, ‘CF Momotaro J’ plants cultivated with K+-supplemented medium showed an increase in the K+ concentration, a decrease in the occurrence of leaf marginal necrosis, and down-regulation of the expression of jasmonate-related genes in tip leaflets. These results indicate that tomato leaf marginal necrosis occurs because of K+ starvation in the tip region of leaflets, leading to the activation of jasmonate-induced signal for necrosis.

  • Takayuki Kobayashi, Katsuhiro Shiratake, Toshihito Tabuchi
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 214-221
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: October 12, 2017
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    Formaldehyde (HCHO) absorption capacity (indicating that HCHO was absorbed into foliage) was measured. Then, the metabolism-related substances (glutathione: GSH) and enzymes (glutathione-dependent formaldehyde dehydrogenase: FALDH and formate dehydrogenase: FDH) in the foliage of wild tomato species were investigated histochemically. In the measurement of HCHO absorption capacity, fresh foliage explant, which was placed in a sealed glass container, was treated with the adjusted 5 ppm HCHO from outside. As a result, in Lycopersicon (Solanum) pennellii LA0716, the HCHO concentration in the glass container significantly decreased down to 0.08 ppm, which is a guideline value indicating the safety of indoor air concentration established by the World Health Organization (WHO). On the other hand, the HCHO concentration of L. chilense TOMATO(WILD)94 did not decrease to the guideline value. Therefore, these results showed that LA0716 was an HCHO “high-absorbing” type in terms of capacity to remove HCHO, and TOMATO(WILD)94 was a “low-absorbing” type. An interspecific difference was observed among the wild tomatoes that were used in this study. In addition, changes in localization of HCHO metabolism-related substances and enzyme activity during treatment with HCHO was observed in the HCHO “high-absorbing” type, but was not shown in the HCHO “low-absorbing” type for each passage of time after HCHO treatment. In our study, we showed the possibility that fresh foliage explant in one wild tomato species, L. (S.) pennellii, absorbed and metabolized “toxic” HCHO.

  • Yoshiyuki Tanaka, Shiho Fukuta, Sota Koeda, Tanjuro Goto, Yuichi Yoshi ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 222-228
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: October 28, 2017
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    Capsinoids are low-pungent capsaicinoid analogues in chili pepper fruits. They exhibit various bioactivities in humans similar to capsaicinoids, but do not produce a nasty burning sensation, encouraging their application in foods and supplements. Previous reports demonstrated that loss-of-function of putative aminotransferase (pAMT) leads to low-pungency and capsinoid accumulation. Therefore, the pamt allele is a useful gene in chili pepper breeding programs to enhance health-promoting properties. Eight loss-of-function alleles have been identified in the Capsicum genus, but the variation in pamt alleles remains to be fully elucidated. In this study, we identified one novel loss-of-function allele from the analysis of low-pungent chili pepper ‘No. 4034’ (C. chinense). ‘No. 4034’ contained mainly capsinoid with an undetectable level of capsaicinoid. A genetic complementation test was conducted by crossing ‘No. 4034’ with other accessions. The results indicated that ‘No. 4034’ possessed a loss-of-function pamt allele. Sequence analysis showed that the novel mutant allele contained a 7-bp insertion (TCGGTAC) in the 16th exon region, which we designated as pamt9. The insertion caused a frameshift mutation and resulted in a truncated protein. Gene expression analysis showed that the expression level of pAMT specifically decreased among biosynthetic genes tested here in ‘No. 4034’, compared with that of pungent accession. pamt9 will be useful for low-pungency and capsinoid breeding, and will provide additional information for variations in pAMT mutants.

  • Yasushi Kawasaki, Tadahisa Higashide
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 229-235
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: November 17, 2017
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    Fruit growth represents the balance between material influxes via xylem and phloem and efflux by transpiration via the stomata of the calyx and cuticle of fruit, which determines the yield and soluble solids content (SSC). Knowledge of these factors is important for the production of high-SSC tomato fruit, but no physiological indicator is available to allow prediction of fruit yield and SSC for breeding and crop production purposes. To identify indicators, we grew Japanese, Dutch, Japanese × Dutch, and high-SSC cultivars and sought correlations of the fluxes to fruit with yield and SSC. To estimate the contributions of the xylem, phloem, and transpiration fluxes to fruit weight increase, we measured 2-day growth rates of intact, detached, and heat-girdled (peduncle steamed for 90 to 120 s) fruits treated at 14, 28, or 42 days after flowering (DAF). Xylem influx was much lower in the high-SSC cultivar than in the others. Phloem influx was lower in the Dutch and hybrid cultivars at 28 DAF. Transpiration efflux was greater in the Japanese cultivar at 42 DAF. Fruit growth rate at 14 DAF was positively correlated with yield, and phloem influx per fruit weight increase at 14 and 28 DAF was positively correlated with SSC. These results show how the xylem, phloem, and transpiration fluxes of fruit can predict fruit yield and SSC. This information will help the production and breeding of high-SSC fruit.

  • Tomoko Hirota, Shinya Yoshida, Takayuki Sawada, Yasunori Nakamura
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 236-249
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: December 19, 2017
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    The black soybean landrace ‘Tanbaguro’, consumed as vegetable seeds (edamame), is characterized by its uniquely high maltose production after heat processing, which is an important trait contributing to its enhanced sweetness. We investigated starch properties related to the maltose production in edamame together with several other affecting biochemical factors. As a result, it was estimated that the low gelatinization temperature of starch predominantly contributed to the increased maltose production and was associated with the increased proportion of short-chain amylopectin, although β-amylase activity did not show any significant correlation with maltose productivity. Additionally, amylose content may promote maltose production by the progression of starch gelatinization together with its effectiveness as a substrate of β-amylase. These starch properties were sensitive to ambient temperature, especially during the latter half of the maturation period. Therefore, it is suggested that maltose productivity in edamame seeds was strongly correlated with the maturing properties of soybean lines. On the other hand, starch content that was insensitive to ambient temperature during the maturing period was also estimated to contribute to the increase in maltose productivity complementarily by multiple regression analysis for varietal difference. These results suggested that starch content showed the additional importance in the varietal difference of maltose productivity among earlier maturing soybean lines than ‘Tanbaguro’.

  • Yoshinori Kanayama, Michiaki Omura, Takeshi Goryo, Tomohisa Shigeta, T ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 250-257
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: December 20, 2017
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    Brassica napus was cultivated in three test fields exposed to different radionuclide contamination levels 1.5 years after the Fukushima Daiichi nuclear power plant accident to investigate the correlation between soil contamination and radiocesium activity concentration (RCs conc.) in plants. The correlations between total and exchangeable RCs conc. were strong in the plow layer (L1) and the layer 5 cm below L1 (L2). Water-soluble radiocesium was not detected in either layer, and little radiocesium penetration was observed below L2. Correlation coefficients between RCs conc. in each plant organ and soil layers were calculated. Correlations between RCs conc. in each vegetative organ and total and exchangeable RCs conc. in L1 and correlations between vegetative organs were mostly strong during vegetative growth and flowering periods. Correlations between RCs conc. in flowers with that in L1, L2, and other vegetative organs were not significant. RCs conc. in L1 may more directly affect concentrations in roots and shoots. RCs conc. in oil extracted from seeds was measured, and the results suggested that radiocesium was not detectable in the oil fraction. Our data regarding radiocesium in soil and plants and their correlations obtained by extensive cultivation in contaminated soils could be useful to gain a better scientific understanding of radiocesium transport and accumulation and to provide useful information for the future utilization of areas with low contamination levels.

  • Naomi Oyama-Okubo, Tomoaki Haketa, Hiroyuki Furuichi, Shunsuke Iioka
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 258-263
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: September 15, 2017
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    A new blue petunia cultivar, TX-794 bred by Takii & Co., Ltd, has a sweet floral fragrance different from conventional petunia cultivars that typically have no odor or have a somewhat unfavorable smell. Since fragrant bedding plants suitable for summer cultivation are rare, we expect that the fragrance will enhance the value of TX-794. The characteristics of emitted scent compounds from TX-794 were evaluated in this study. The major scent compound was phenylacetaldehyde, a C6-C2 aromatic compound that was emitted at higher levels in TX-794 compared to conventional petunia cultivars. iso-Eugenol, a C6-C3 aromatic compound, is the major scent compound in conventional petunia cultivars. These results suggest that TX-794 has a high capacity to biosynthesize C6-C2 aromatic compounds, resulting in a significantly different scent compound composition compared to conventional petunia cultivars. Time-course analysis of scent compound emission revealed that the largest release of scent compounds by TX-794 occurs during the switch from light periods to dark periods. Soon after flowering, that is, in the light period on the day of anthesis, the major scent compound was p-cresol. Thereafter, the primary scent compound was phenylacetaldehyde or methyl benzoate with 2-phenylethanol occupying the next position. Since a bed or a container of petunias has flowers that are primarily over 2-days old, the basic fragrance of TX-794 plants is derived from phenylacetaldehyde, which has a hyacinth-like scent, 2-phenylethanol, which has a rose-like scent, and methyl benzoate, which has a dry fruit-like scent.

  • Takamitsu Waki, Masaharu Kodama, Midori Akutsu, Kiyoshi Namai, Masayuk ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 264-273
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: September 29, 2017
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    Double flower and hortensia (mophead) hydrangea (Hydrangea macrophylla (Thunb.) Ser.) traits are recessively inherited. Cross breeding of these traits in hydrangea is difficult because it takes about two years from crossing to flowering. In this study, we aimed to obtain DNA linkage markers that would allow accelerated selection of these traits. We used next-generation sequencing to comprehensively collect DNA sequences from the ‘Kirakiraboshi’ with a double flower and lacecap inflorescence and the ‘Frau Yoshimi’ with a single flower and hortensia inflorescence, and designed simple sequence repeat (SSR) primer pairs for map construction. We screened 768 SSR primer pairs in 93 F2 progeny derived from ‘Kirakiraboshi’ and ‘Frau Yoshimi’. We identified 147 loci, which were expanded to 18 linkage groups with a total map length of 980 cM. Linkage analysis identified that both the double flower trait from ‘Kirakiraboshi’ (dKira) and the hortensia trait from ‘Frau Yoshimi’ (hFrau) were located on linkage group KF_4. Detailed linkage analysis using 351 F2 progeny revealed a 34.8 cM map length between the two loci and identified two tightly linked SSR markers, STAB045 for dKira and HS071 for hFrau. Genetic analysis suggested that double flower and hortensia traits are each controlled by a single recessive gene. Together, the linkage map, SSR markers, and genetic information obtained in this study will be useful for future hydrangea breeding.

  • Yoshikuni Kitamura, Sachiyo Ueno, Hiroe Aizawa, WeiWei Teoh
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 274-280
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: December 20, 2017
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    Two types of cut hydrangea flowers are marketed: Fresh-stage cut flowers (harvested just after the decorative sepals are completely colored before or during flowering) and antique-stage cut flowers (harvested when the decorative sepals become green and/or red after flowering). We investigated the differences in vase lives between fresh- and antique-stage cut flowers using 10 cultivars and 5 lines of hydrangea. The antique-stage cut flowers of ‘Endless Summer’, ‘Glowing Alps’, ‘Grünherz’, ‘Masja’, ‘Temari Ezo’, and line No. 2 exhibited significantly longer vase lives than their fresh-stage cut flowers. The difference in vase lives between the cut flowers of ‘Masja’ harvested at two different stages was approximately 60 days. We conducted further studies to elucidate the contribution of detailed differences in the harvest stages to differences in the vase lives using ‘Masja’ and ‘Xi’an’. Vase lives were compared among the cut flowers harvested at four different harvest stages that were divided based on flowering of florets and greening of the decorative sepals. The cut flowers of ‘Xi’an’ harvested at the decorative florets flowering- and decorative sepal greening-stages showed significantly longer vase lives than those harvested at the non-decorative floret flowering stage. The cut flowers of ‘Masja’ harvested at two harvest stages following the beginning of the decorative sepal greening stage exhibited significantly longer vase lives than those harvested at the other two harvest stages. A recutting treatment rescued the cut flowers harvested at the decorative sepal greening completed-stages that exhibited softening of the decorative sepals. This result suggested that the vase lives of cut hydrangea flowers were terminated by the disruption of water balance caused by vessel occlusion in the stem ends. In conclusion, a relatively longer vase life can be expected when cut hydrangea flowers are harvested after flowering of the decorative florets. However, we should note that cut flowers of some cultivars harvested at the decorative floret flowering stage may exhibit relatively short vase lives. Treatments that suppress vessel occlusion may be effective for lengthening the vase lives of cut hydrangea flowers.

  • Ryohei Nakano, Hidemi Akimoto, Fumio Fukuda, Takashi Kawai, Koichiro U ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 281-287
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: October 12, 2017
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    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.

  • Yusuke Kamiyoshihara, Takuya Nakamura, Yasuharu Itagaki, Shinichi Asad ...
    Type: Original Articles
    2018 Volume 87 Issue 2 Pages 288-296
    Published: 2018
    Released: April 18, 2018
    [Advance publication] Released: February 01, 2018
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    Actinidin is a major protein contained in kiwifruit (Actinidia spp.). While uptake of actinidin is beneficial to help gastric protein digestion with cysteine protease activity, the protein is also recognized as a major elicitor of allergy which can induce tingling in the oral cavity and occasionally severe anaphylactic reactions. Given that consumption of fresh kiwifruit has increased globally, development of Actinidia cultivars with lower level of actinidin is required to reduce the risk of allergenicity. In the present study, we examined variations in the actinidin level in Actinidia varieties. Among several varieties having trace amounts of actinidin, A. chinensis ‘Kohi’ was targeted to be analyzed for the molecular basis for the phenotype. ‘Kohi’ had below the detectable transcript level of Act1a, a critical gene for actinidin level. The upstream region of Act1a in ‘Kohi’ constituted different sequences from that of A. deliciosa ‘Hayward’, which has an active promoter for high expression of Act1a. The ‘Kohi’ sequence in the diverged region (upstream from −873 b) was rich in cytosine residues methylated at a higher level than in ‘Hayward’. Our data suggest the possibility of novel epigenetic regulation to reduce the actinidin level. The molecular mechanism for the phenotype in ‘Kohi’ was differentiated from ‘Hort16A’, a globally popular cultivar with a low level of actinidin. This cultivar could be a choice as a genetic resource in breeding to develop cultivars with controlled actinidin levels.

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