Horticultural Research (Japan)
Online ISSN : 1880-3571
Print ISSN : 1347-2658
ISSN-L : 1347-2658
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Breeding & Germplasm Resources
  • Naoya Hamabe, Akiko Baba, Minori Maeda, Hiroyuki Katsuoka, Motohiro Ta ...
    2020 Volume 19 Issue 3 Pages 229-235
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    ‘Koyama New Summer’ is a bud mutation of ‘Hyuganatsu’ (Citrus tamurana hort. ex. Tanaka), which has the characteristic of producing more seedless fruits than ‘Hyuganatsu’. We examined the cause of seedlessness in ‘Koyama New Summer’. In the self-pollination process of ‘Koyama New Summer’ and ‘Hyuganatsu’, the pollen tube elongation stopped in the upper part of the style, and there was no significant difference between the two. This indicates that ‘Koyama New Summer’ has self-incompatibility like ‘Hyuganatsu’. The fruit setting rate after physiological fruit drop of ‘Koyama New Summer’ under the non-pollen condition was 60.8%, being higher than in ‘Nishiuchi Konatsu’, ‘Muroto Konatsu’, and ‘Hyuganatsu’. This indicates that ‘Koyama New Summer’ has highly parthenocarpic traits compared with ‘Nishiuchi Konatsu’, ‘Muroto Konatsu’, and ‘Hyuganatsu’. In addition, parthenocarpy in ‘Koyama New Summer’ gives rise to autonomic parthenocarpic traits because it was induced under non-pollen and non-agent-administered conditions. In conclusion, after examining the causes of seedlessness in ‘Koyama New Summer’, it was determined that it exhibits not only self-incompatibility but also highly autonomic parthenocarpic traits.

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  • Takayuki Mizuno, Risa Nakane, Takashi Kaidzuka, Yuko Ishikawa-Takano, ...
    2020 Volume 19 Issue 3 Pages 237-245
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    Red welsh onion (Allium fistulosum L.) ‘Hitachi-benikko’, which has red leaf sheaths, was bred by Ibaraki Agricultural Center as a commercial vegetable in Ibaraki Prefecture. In this study, four anthocyanins including a novel glycoside [cyanidin 3-O-(3″-O-acetyl-6″-O-malonyl)-glucoside] and five flavonols were isolated and characterized by chemical and spectroscopic methods. The novel anthocyanin was the main component in the underground part of ‘Hitachi-benikko’. Of these flavonols, four were identified as quercetin and its glycosides, which are known to exhibit marked antioxidant activity. Furthermore, we measured the polyphenol content and antioxidant activity (H-ORAC) of the aerial and underground parts of ‘Hitachi-benikko’ and compared them with those of another general welsh onion cultivar. As the results, the reddish underground parts of ‘Hitachi-benikko’ showed higher polyphenol contents and antioxidant activities than the aerial parts of ‘Hitachi-benikko’ and those of the general welsh onion cultivar. These results promote the value of red welsh onion cultivar ‘Hitachi-benikko’ as a vegetable.

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Propagation & Transplant Production
  • Shiro Mori, Daisuke Ando, Toshiaki Kaeriyama, Tomo Oomiya
    2020 Volume 19 Issue 3 Pages 247-252
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    The Asiatic hybrid lily ‘Kitakirari’ has a division-type bulb that produces multiple flower stalks, and bulbs for cut flower production are cultivated for 2 or 3 years in an open field. The division-type bulb forms bulblet primordia on the stalk axis in the mother bulb, and then the bulblets enlarge; as a result, the bulb divides. In this study, the effects of temperature on ‘Kitakirari’ division in bulb production were investigated with the bulblet attached to biennial plants. In experiment 1, the effects of temperature before freezing storage on bulb quality in the final stage of bulb production were investigated. When the bulbs were treated at 8°C for 12 weeks before freezing storage, many non-standard bulbs were observed. The non-standard bulbs had five or more bulblets in the mother bulb and were not suitable for use in cut flower production. In contrast, non-standard bulbs were not found in the treatment group that was promptly frozen and stored at –2°C. In experiment 2, although temperature treatments after freezing storage did not affect the number of bulblets in the mother bulb, the bulb weight in the high-temperature group (heat cultivation at 15°C) was significantly heavier than in the low-temperature group (cultivation in the open field), and the bulb width was also significantly greater than in the low-temperature group.

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Crop Production & Cropping Type
  • Atsushi Matsumura, Yuki Nagasawa, Kanako Hirase, Hiroyuki Masumoto
    2020 Volume 19 Issue 3 Pages 253-260
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    This study was carried out to examine the effects of shoot and root pruning treatments on the yield of green soybean. First, the influences of shoot and root pruning during the nursing period on the yield of green soybean were investigated. The results showed that neither pruning treatment led to better yields than the control. In the next experiment, shoot pruning at the fifth leaf stage led to no difference in yield between the shoot pruning treatment and control (non-shoot pruning). Finally, the influences of root pruning at transplanting on shoot growth and yield were investigated. The results showed that 1/2 root pruning has positive effects on the number of pods and yield compared with the control in the summer season. Heavy root pruning, however, had no effect on the yield. These results suggest that shoot pruning leads to no marked increase in yield, but root pruning at transplanting is effective to improve the productivity of green soybean in the summer cropping season.

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  • Kazuki Tsuge, Satoru Motoki
    2020 Volume 19 Issue 3 Pages 261-268
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    “Norabona” is a Brassica napus L. leafy vegetable landrace that is grown in Kawasaki City of Kanagawa Prefecture, Japan. The main stems of norabona are pinched at the beginning of the harvest period, and the flower stalks (lateral shoots), which grow immediately after this, are harvested. However, few studies have been conducted on pinching of the main stems, which may influence the yield, in the Brassica leafy vegetable and norabona. In the present study, a survey including four trials, performed in different years, was conducted to examine the effects of pinching of norabona’s main stems, and the influences of differences in the timing and position of pinching of the main stems on the yield. The number of flower stalks, total yield, total biomass, and yield of salable products were significantly higher when the main stems were pinched at the beginning of the bolting stage (the stems had been growing but no buds had been identified). When pinching was conducted at the beginning of the bolting stage and the pinching position was low (close to the earth and half the number of true leaves in stock were removed), the total biomass in the trial of 2017 was smaller than when the pinching position was high (one quarter the number of true leaves in stock were removed), but half or fewer trials showed no significant differences in the total biomass. Furthermore, the mean weight of the flower stalk in the early harvest period was significantly greater when the pinching position was low.

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  • Takashi Tsukamoto, Satomi Ishii, Sayuri Tanabata, Nobuo Suzui, Naoki K ...
    2020 Volume 19 Issue 3 Pages 269-275
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    The translocation of photoassimilate from intact tomato plant lateral shoot leaves and their rate of contribution to the soluble solid content of tomato fruit were investigated using 11CO2 and a positron-emitting tracer imaging system (PETIS). After 11CO2 application to the 4th leaf of the lateral shoots or to the leaf just below the fruit truss in the main shoots, 11C translocation to the fruits began after about 40 min and 1 hour, respectively. The contribution of lateral shoot leaves to photoassimilate translocation to the fruits was based on the amount of 11C translocated from the 7th, 8th, and 10–12th leaves of the main shoots and the 1st–4th leaves of the lateral shoots to the fruits. This contribution, expressed as a rate, of the 1st–4th leaves of the lateral shoots to photoassimilate translocation to the fruit was 44.6–80.1%. The photosynthetic rate of the 4th leaf of the lateral shoots was higher than that of the leaf just below the fruit truss. These results show that the lateral shoot leaves significantly contribute to the translocation of photoassimilate to fruits, and so leaving the lateral shoots may increase the soluble solid content of tomato fruit.

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  • Taishi Kadota, Akihiko Kataoka, Jyunpei Shibuya, Naoko Fukuta, Ayuko U ...
    2020 Volume 19 Issue 3 Pages 277-284
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    Winter cultivation of Eustoma grandiflorum is commonly associated with flower bud blasting, leading to a reduced cut flower quality. CO2 enrichment is expected to alleviate this problem. In this study, we investigated the effects of CO2 enrichment on cut flower quality of E. grandiflorum, cultivated during winter in a greenhouse located in Kochi Prefecture, where the controlled daytime temperature was 25°C. Plants were cultivated under three greenhouse conditions: (i) without CO2 enrichment and under a controlled daytime temperature of 25°C (non-enriched/25°C), (ii) with CO2 enrichment and under a controlled daytime temperature of 25°C (enriched/25°C), and (iii) with CO2 enrichment and under a controlled daytime temperature of 30°C (enriched/30°C). The harvest dates of enriched/30°C were earlier than those of non-enriched/25°C. The two treatments with CO2 enrichment caused increases in the cut flower length and number of flowers. We clarified that the improvement of cut flower quality in enriched/25°C was approximately equivalent to that in enriched/30°C, although the CO2 concentration during the daytime was maintained at 1,000 ppm for a shorter time in enriched/25°C than in enriched/30°C as the ventilation windows of the greenhouse were kept open for a longer time in the former treatment.

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  • Takashi Baba, Yuki Moriya, Daisuke Sakamoto, Toshio Hanada, Hiroshi Iw ...
    2020 Volume 19 Issue 3 Pages 285-292
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    Crop load to avoid alternate bearing was investigated in 5-12786 columnar apples. Alternate bearing started from three years after first bearing. For five years from the first bearing, more than 90% of trees whose crop load was smaller than three fruits per cm2 of the trunk cross-sectional area (TCA) showed increases in the flower bud number and yield. However, eight-years-old trees being thinned to give yield two–three fruits・cm–2 of TCA at 30 days after full bloom showed less than 10% terminal flower bud formation. Compared with treatment to distribute fruits throughout whole branches, the number of terminal flower buds decreased with treatment to localize fruits in parts of the tree. To predict the frequency of terminal flower buds, the best indicator of crop load was the fruitlet cluster/fruit ratio, and the fruiting part length/fruit ratio was the second. Regarding to habits of terminal flower bud formation, long vigorous shoots more frequently formed flower buds than spur-like shoots. Because fruiting shoots mostly consist of the latter, methods to promote flower bud formation of spur-like shoots should be developed. To understand adequate crop load of columnar apples, more varieties need to be examined while considering the influence of fruit distribution and the control of long shoots.

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  • Sakura Hamasaki, Ittetsu Yamaga, Takuma Furuya, Rin Kudaka, Mao Seoka, ...
    2020 Volume 19 Issue 3 Pages 293-298
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    It was previously reported that the content of β-cryptoxanthin in juice sacs of Satsuma Mandarin was increased by mulching cultivation. In this study, to further clarify the mechanisms of mulching regulating β-cryptoxanthin accumulation, the effects of mulching on the expression of carotenoid metabolic genes were investigated in the juice sacs of Satsuma Mandarin ‘Aoshima unshiu’, which were planted in two different fields (Fields A and B) of Shimizu-ku, Shizuoka. In the mulching treatment, the β-cryptoxanthin content in the juice sacs and flavedo was 30 and 50% higher than that of the control, respectively. The changes in expression of carotenoid biosynthetic genes by mulching were different between the two fields. In fieldA, the expression of CitZDS was up-regulated, while the expression of CitHYb and CitZEP was down-regulated by mulching treatment in juice sacs. In fieldB, the expression of CitPSY, CitZDS, CitLCYb1, CitLCYb2, CitHYb, CitZEP, CitNCED2, and CitNCED3 in juice sacs was significantly up-regulated by mulching treatment. In particular, the transcript levels of the upstream carotenogenic genes were much higher on mulching treatment in fieldB. These results suggest that the transcription of carotenoid biosynthetic genes in Satsuma Mandarin is induced by mulching treatment. In addition, the high expression of upstream carotenogenic genes (high-level supply of β-carotene) was considered to be a key mechanism leading to the marked accumulation of β-cryptoxanthin in juice sacs treated by mulching.

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Postharvest Physiology & Technology
  • Takahiro Furuta, Manabu Wanaka, Shohei Kumamoto, Hirokazu Ikenaga, Rei ...
    2020 Volume 19 Issue 3 Pages 299-307
    Published: 2020
    Released: September 30, 2020
    JOURNALS FREE ACCESS

    The combined effect of 1-methylcyclopropene (1-MCP) application on CO2 exposure for astringency removal and packaging techniques on suppressing fruit softening during marine transport bound for southeast Asia was tested in early-maturing persimmon, ‘Nakatani-Wase’ fruit. In tests while simulating marine transport, 1-MCP application in combination with all packaging techniques tested in this experiment effectively suppressed the softening of fruit. Under conditions simulating the shelf-life after arrival, the combination of 1-MCP application and modified atmosphere (MA) packaging at both individual fruit and carton box levels suppressed fruit softening for 7 days at room temperature and for more than 10 days at 5°C. On the other hand, fruit packaged in normal carton boxes or boxes coated with water-impervious material softened immediately after arrival at room temperature and after 5 days at 5°C. Practical transport tests involving marine transport bound for Singapore confirmed that the combination of 1-MCP application and MA packaging in carton boxes led to the complete absence of softened fruit upon arrival in Singapore and reduced it to just 13.3% 6 days after transfer to room temperature. These results indicate that the combination of 1-MCP application, MA packaging, and a reefer container for temperature control is a practical quality control technique for marine transport of ‘Nakatani-Wase’ fruit bound for southeast Asia.

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