Horticultural Research (Japan)
Online ISSN : 1880-3571
Print ISSN : 1347-2658
ISSN-L : 1347-2658
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REPORTS
Breeding & Germplasm Resources
  • Shigeru Satoh, Nakao Kubo, Kaei Nakatani
    2020 Volume 19 Issue 1 Pages 1-6
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    Twelve cultivars of heirloom red turnips that have been cultivated in Shiga Prefecture were separated into two groups: one group consisted of seven cultivars and contained pelargonidin, coloring reddish vermilion, and the other group had five cultivars and contained cyanidin, coloring reddish purple. The former group was present in the northern and north-western land areas and the latter in the eastern land area of Lake Biwa. Anthocyanin was generally present over the whole surface of the pelargonidin-containing turnips, whereas it was limited to mainly the above-ground part in the cyanidin-containing turnips. The former group contained more anthocyanin per unit volume of the colored surface tissue than the latter. Among the cyanidin-containing turnips, ‘Shinshukabu’ gave a UV-VIS absorption spectrum similar to ‘Kisobenikabu’ that originated in Nagano Prefecture, confirming a previously postulated relationship between the two turnips.

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Crop Production & Cropping Type
  • Keita Watanabe, Masaru Nishino, Takeshi Kanto, Kaichi Uchihashi, Fumio ...
    2020 Volume 19 Issue 1 Pages 7-12
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    The application of UV-B (Ultraviolet-B) to tomatoes (Solanum lycopersicum) cv. ‘House-momotaro’ and ‘Redore’ grown in forcing culture was investigated in order to induce resistance to disease and reveal any damage to yield. Irradiation with UV-B was performed every night between 11 pm and 2 am with an intensity of 2.30 to 12.56 μW・cm–2. As a result, the shrinkage of irradiated leaves, increase of the dry matter ratio of leaves and stems, and induction of burned fruits were observed in both cultivars. The UV-B irradiation of plants had no influence on the days from planting to blooming, fruit set ratio, or yield of fruits. Both an increase of brix and decrease of acidity were observed in fruit juices from irradiated plants. The UV-B irradiation had no effect on the fruit coloring or lycopene content of fruits.

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  • Masami Asai, Kenji Murakami
    2020 Volume 19 Issue 1 Pages 13-19
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    In this study, we investigated the relationship between onion growth during snow cover and varietal differences in soluble carbohydrate accumulation and survival rates after snow melting. The survival rate after melting differed among varieties and was highest in ‘Tarzan’ suggesting that overwintering ability under snow differs according to the variety. No relationship was found between the survival rate after snow melting and size of the plant from the beginning of snow cover to after melting. At the beginning of snow cover, soluble carbohydrate accumulation of the leaf sheath was about twice that of the leaf blade. The leaf sheath accumulated a larger amount of polymerized fructan compared with the leaf blade. The soluble carbohydrate accumulation decreased from the beginning of snow cover until melting. The kestose content (1-kestose plus neokestose) of the leaf sheath after melting was also determined; here too it was highest in ‘Tarzan’. The findings suggest that fructans—especially residual fructans in the leaf sheath—are important for survival and growth following snow melting. Consistent with this, the consumption of soluble carbohydrates by onions growing in snow was low, and it is considered that this affects the amount of residual fructan after melting. The results suggest that the metabolism of soluble carbohydrates during snow cover is related to the overwintering ability of onions under snow. ‘Tarzan’, which has little soluble carbohydrate content during snow cover and retains fructan after snow melting, and has a high overwintering ability, suggesting that it is a suitable variety for autumn-sowing cultivation in snowy areas.

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  • Tomoaki Toya, Yoshiharu Fujii, Takeshi Suzuki
    2020 Volume 19 Issue 1 Pages 21-27
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    We applied the rhizosphere soil assay method used for asparagus, and conducted the following tests to establish a soil sickness risk evaluation method for the Japanese pear. First, when we measured the pear soil gradually diluted with non-pear soil with the rhizosphere soil assay, the inhibition rate of soil decreased from 75.6 to 18.3% according to the level of dilution (y = 12.9ln(x) + 11.5, r = 0.97, x: proportion of pear soil, y: percentage of soil inhibition). In addition to this, in the same way as the above-mentioned test, we gradually diluted the pear soil with non-pear soil, and we planted an annual nursery of pear. As the results, the growth of shoots increased accordingly. Therefore, it was clear that the rhizosphere soil assay method was effective as a technique to evaluate the risk of soil sickness for the pear. On the other hand, when we measured the soil around a pear tree planted in the field with the rhizosphere soil assay method, it was revealed that there is a difference in distance and depth.

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Growth Regulation
  • Kenichi Matsuda, Ayako Katayama-Ikegami, Narumi Higashi, Kanoko Sakai, ...
    2020 Volume 19 Issue 1 Pages 29-38
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    The effects of temperature on the color of ‘Ruby Roman’ grape berry skin in 5-year-old potted trees were investigated. Thirty-six trees were divided into six groups: five groups received low-temperature treatment (28°C/20°C, day/night) at different developmental stages: at 54 (13 days after veraison) to 63 days after full-bloom (DAFB) (54 DAFB group); 63–72 DAFB (63 DAFB group); 72–81 DAFB (72 DAFB group); 81–90 DAFB (81 DAFB group); 54–90 DAFB (low-temperature control, 28°C/20°C); and one group received high-temperature treatment (35°C/27°C) at 54–90 DAFB (high-temperature control). Before and after treatments, the trees were kept under high-temperature conditions. After treatment, color change including the color chart value and concentration of anthocyanin in berry skin were the highest in the 63 DAFB group, followed by the 72 DAFB group. For harvested berries, the low-temperature control group had the deepest skin color, whereas the high-temperature control and 54 DAFB groups had the lightest skin colors. These results indicate that the color of ‘Ruby Roman’ berry skin is enhanced by exposure to low temperature after 63 DAFB and is the most sensitive to low temperature from 63 to 80 DAFB. Gene expression analysis showed higher expression levels of the VlMybA1-2 and VlMybA1-3 genes in the high-temperature than in the low-temperature control group. However, the expression levels of VviF3′H and VviF3′5′H2 immediately following low-temperature treatment in the 63 and 72 DAFB groups were higher than in both control groups. These findings suggest that the decrease in anthocyanin accumulation under high-temperature conditions might not be controlled by VlMybA1 transcriptional factors, and that a different mechanism may be involved in regulation of the biosynthesis of anthocyanin in ‘Ruby Roman’ grape berry skin.

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  • Kenichi Matsuda, Ayako Katayama-Ikegami, Narumi Higashi, Kanoko Sakai, ...
    2020 Volume 19 Issue 1 Pages 39-47
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    The effects of temperature on the color of detached ‘Ruby Roman’ grape berries at different developmental stages after véraison were investigated. The berries were collected from grapevines at 50 days after full-bloom (DAFB), 60 DAFB, 70 DAFB, and 80 DAFB, and incubated at 18°C, 21°C, 24°C, 27°C, and 30°C for ten days, respectively. The color chart value increased after treatment compared with that before treatment under all temperature conditions at 50 DAFB, 18–24°C at 60 and 70 DAFB, and 18°C at 80 DAFB. These results indicate that the color of ‘Ruby Roman’ grape berry skin is enhanced by exposure to lower temperatures after 60 DAFB, and that the closer the berry is to maturity, the higher is its requirement for low temperatures to achieve the desired color. We performed an analysis of abscisic acid (ABA) metabolites and expression of genes involved in anthocyanin biosynthesis in the berry skins. The findings of the analysis indicated that the exposure to high temperature (30°C) increased the biosynthesis of ABA and expression of the VlMybA1 genes. In addition, expression of the anthocyanin biosynthesis-related structural genes, such as VviF3′5′H2 and VviFAOMT, was more accelerated at a low temperature of 18°C at 50 and 60 DAFB than at 70 and 80 DAFB. Therefore, anthocyanin accumulation in ‘Ruby Roman’ berry skin under different temperature conditions is not directly related to the endogenous ABA concentration and VlMybA1s expression levels, but may be related to ABA signal transduction, the substrates of anthocyanin biosynthesis and activities of related enzymes, and (or) other different factors.

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  • Manabu Nishiyama, Hiromichi Yamazaki, Yoshinori Kanayama
    2020 Volume 19 Issue 1 Pages 49-54
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    The effect of light quality on flowering in everbearing strawberry (Fragaria × ananassa Duch.), a long-day plant, was investigated under night illumination conditions. Two everbearing strawberry cultivars, ‘Natsuakari’ and ‘Suzuakane,’ were tested. Flowering was promoted under far-red light, but it was almost inhibited under red light at 30/25°C (day/night temperature) in a natural light type phytotron. In another treatment, plants were grown under night illumination in a glass house from September. In this case, flowering was reduced under red light conditions compared with under an incandescent lamp. In everbearing strawberry cultivation, flowering is markedly promoted and plants may die due to self-topping under high temperature and long-day conditions. However, the mortality rate due to self-topping was lower under red light in this study. These results reveal the flowering response of everbearing strawberry cultivars to red and far-red light under relatively high temperatures, and the possibility of using red light to maintain vegetative growth by regulating flowering.

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  • Shuichi Date, Satoshi Terabayashi
    2020 Volume 19 Issue 1 Pages 55-60
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    The aim of this study was to obtain basic information about the frequency of adventitious shoot generation on main vein tissue at the leaflet connection part in tomato (Solanum lycopercicum L. cv ‘Momotaro’) and their generating loci. Tomato plants were cultivated hydroponically and all lateral buds were removed at the start of their elongation, in the same way as conventional cultivation, and all clusters were also removed at the anthesis of their first flower. The frequency of adventitious shoot formation on main vein tissue at the leaflet connection part in each leaf node, and furthermore, the sugar and starch contents in main vein tissue of the leaves in odd-numbers and Brix in those in even-numbers were investigated. Most adventitious shoots were generated from the main vein tissue at the connection part including a large and decompound leaflet. The leaves at higher nodes up to the 10th leaf had a higher frequency of adventitious shoots, whereas those above the 11th leaf were not significant. Additionally, the frequency of adventitious shoots from the main vein tissue at the connection part, a pair of large and decompound leaflets closest to the stem, was lower. Starch content in main vein tissue of the leaves in odd-numbers showed a similar trend line as the frequency of adventitious shoot formation. A significantly positive correlation was noted between the starch contents of the leaves in odd-numbers less than 0.6 mg starch・gFW–1 and the frequency of adventitious shoots generated from the main vein tissue at the connection part of large and decompound leaflets. These results suggest that the frequency of adventitious shoots generated from main vein tissue at the connection part of large and decompound leaflets of tomato was affected by the accumulation of starch, especially at a concentration of 0–0.6 mg starch・gFW–1 in the main vein tissue. Moreover, the frequency of adventitious shoot formation at the connection part with especially large and decompound leaflets was different with variable distances from the stem.

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Postharvest Physiology & Technology
  • Takashi Kawai, Kagari Akita, Sakine Watanabe, Yosuke Fukamatsu, Daisuk ...
    2020 Volume 19 Issue 1 Pages 61-67
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    Flesh texture of peach (Prunus persica (L.) Batsch) is one of the most important traits regarding post-harvest preservation and consumer preference. Melting flesh peaches show a typical climacteric type of ripening characterized by a burst of ethylene production and rapid loss of firmness in the late maturing stage. In contrast, stony hard peaches produce little ethylene and maintain flesh firmness on the tree and after harvest. Here, we demonstrated that ‘Tosui’ peach, which is selected from open-pollinated seedlings of ‘Kawanakajimahakuto’, bears stony hard characteristics. ‘Tosui’ peach shows a long shelf life and crisp flesh; however, its ethylene production and softening characteristics remain unclear. We investigated the change of ethylene production and flesh firmness of ‘Tosui’ peach treated with or without exogenous propylene, an ethylene analogue. In non-treated control fruit, little ethylene production was detected and marked flesh firmness was maintained irrespective of the harvest season and production area. Although the flesh firmness was significantly reduced by propylene treatment, little ethylene production was detected during fruit softening. Analysis of the PpYUC11 gene, a strong candidate for the stony hard phenotype in peaches, revealed that the genotype of the transposon insertion of the 5′-flanking region and simple sequence repeat (SSR) of the first intron of ‘Tosui’ is the same as that of other stony hard peaches. These results collectively suggest that ‘Tosui’ is a stony hard peach whose ethylene production and resulting loss of firmness are suppressed.

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  • Kiyohide Kojima, Takuma Ishibashi, Tatsuya Matsumoto, Daigo Andou
    2020 Volume 19 Issue 1 Pages 69-74
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    Functional substances in young fruits (fruit thinning time) and picking fruits (including after ripening and removal of astringency) of ‘Le Lechier’, ‘Hiratanenashi’, ‘Akatsuki’, and ‘Kosui’ and pruned branches and deciduous leaves of ‘Le Lechier’ and ‘Kosui’ were analyzed. The polyphenol concentration was higher in the peel of all fruits in the picking fruits, but the concentration tended to decrease overall compared with the young fruits. In ‘Le Lechier’ and ‘Kosui’, the polyphenol concentrations were at the same level for the pruned branches and deciduous leaves. The concentrations of flavans were high in the peels of ‘Le Lectier’ and the peels and flesh of ‘Hiratanenashi’ in the young fruits. In the harvested fruits, the peel was higher in all varieties, in particular, the peels of ‘Le Lectier’ had a high concentration, showing the same tendency as the polyphenol concentration results. The radical scavenging ability was high in the flesh of young fruits. However, the picking fruits tended to decrease compared with the young fruits. The scavenging ability was also observed in the deciduous leaves of ‘Le Lechier’ and ‘Kosui’. The presence of chlorogenic acid was detected in the peels and flesh of ‘Le Lectier’ and ‘Kosui’ in the young fruits, and in the peels and flesh of ‘Le Lectier’, ‘Kosui’, and ‘Akatsuki’ in the picking fruits.

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  • Noriko Toyohara, Akane Higashi, Tanjuro Goto
    2020 Volume 19 Issue 1 Pages 75-82
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    Dutch iris ‘Blue Magic’ cut flower rapidly loses iris ornamental value in a vase. In this experiment, we distinguished between two factors: incomplete flowering and tepal senescence, and further investigated the effects of the flower bud development level at harvest, storage method, and pretreatment with gibberellin (GA3) and benzyladenine (BA) as a stem dip. Incomplete tepal development in a vase occurred regardless of the flower bud development level at harvest. As the 10°C dry storage period exceeded 2 days, the tepal development was suppressed and the vase life was shortened. As with dry storage, the longer the storage period, the shorter the ornamental period even in wet storage. Application of a 100-ppm concentration of GA3 as a stem dip to the cut flower which had been stored under dry conditions for 1 day, promoted tepal development. However, when the same GA3 treatment was applied to flowers which had been stored under dry conditions for 3 days, its flowering was not promoted. The application of BA or mixture of BA and GA3 inhibited senescence and shrinking of the tepal, leading to a prolonged flower vase life.

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NEW TECHNOLOGY
  • Michio Hamada, Mikio Shiraishi
    2020 Volume 19 Issue 1 Pages 83-88
    Published: 2020
    Released: March 31, 2020
    JOURNALS FREE ACCESS

    Using a digital camera equipped with a fisheye lens and the image processing free-software “Fiji-Image J”, we developed a new protocol for determination of the leaf area index (LAI) of table grapes with the same level of measurement accuracy as the plant canopy analyzer (PCA). A regression analysis between the leaf width (X) and single leaf area (Y) indicated highly significant values (Y = 0.5716X2.0425, R2 = 0.99**). A highly significant correlation was obtained between the actual LAI and the LAI measured by PCA (r = 0.964**). Regarding “Fiji-Image J”, we performed the following three-step image processing: (1) R-, G-, and B-separation of the original image taken, (2) correction of the three separated images by “Subtract background algorithm” and “Minimum” threshold treatment mode, (3) calculation of cumulative vegetation rate in the three images. As the range of LAI values was 1 to 4, a highly significant linear correlation was noted between the cumulative vegetation rate (X) and actual LAI (Y): Y = 0.0769X − 18.325, R2 = 0.82**.

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