The Horticulture Journal
Online ISSN : 2189-0110
Print ISSN : 2189-0102
ISSN-L : 2189-0102
Advance online publication
Displaying 1-8 of 8 articles from this issue
  • Kaori Nakajima, Kyoushiro Okamoto, Taishi Hayashida, Kazuyoshi Nada, S ...
    Article type: Original Articles
    Article ID: QH-155
    Published: 2025
    Advance online publication: October 25, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Japanese pear [Pyrus pyrifolia (Burm. F.) Nakai] has a S-RNase-based self-incompatibility system and inactivation of S-RNase causes self-incompatibility breakdown in this system. Copper ions (Cu++) strongly inhibited the RNase activity of crude stylar proteins, but did not overcome self-incompatibility in the Japanese pear ‘Kosui’ (S4S5). To elucidate the cause of this phenomenon, the present study aimed to separate stylar RNases and clarify their responses to Cu++ in ‘Kosui’. Using an anion exchange chromatograph equipped with a Mono-Q column, one strong non-S-RNase was separated, and at least six non-S-RNases together with 2 S-RNases were isolated, by cation exchange chromatography with the Mono-S column. S-RNases were identified by dot blot analysis using S-RNase antiserum, and hereafter, the seven non-S-RNases isolated are designated as NS1 to NS7 in eluting order. NS1 and NS2 were abundant RNases with strong activities, and their activities were reduced to 6.6 and 4.5% of the control by 1 mM CuSO4, respectively. NS3, NS4, NS5, NS6, and NS7 were weak RNases, and NS7 showed intermediate inhibition (31%) with Cu++, whereas inhibition of other RNases was weak, from 44 to 74% of the control. Meanwhile, the degree of inhibition was quite low in S4- and S5-RNase (86 to 89%). Thus, RNase inhibition of crude stylar proteins by Cu++ is due to strong repression of NS1 and NS2 activities. These results indicate that active S-RNase can cause a self-incompatibility reaction despite large decreases in non-S-RNase activities in the pear style.

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  • Hayato Morimoto, Kenichi Shibuya
    Article type: Original Articles
    Article ID: SZD-006
    Published: 2025
    Advance online publication: October 23, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Autophagy is a conserved system responsible for the degradation of intracellular components and remobilization of nutrients in eukaryotes. Autophagy-like processes have been observed in senescing petals of several plant species. Further, significant expression levels of autophagy-related genes are induced along with an increase in ethylene production in flowers that show ethylene-dependent senescence. However, knowledge of autophagy-like processes in ethylene-independent flower senescence remains limited. In this study, we isolated autophagy-related genes (LhATG5, LhATG6, five LhATG8 homologues, and LhATG10), and analyzed their expression levels during tepal senescence in the Oriental hybrid lily, which shows ethylene-independent senescence. The transcript levels of LhATG5, LhATG6 and LhATG8s, but not LhATG8e, increased as tepals senesced. Furthermore, we observed cellular structures stained with monodansylcadaverine (MDC) dye, which stains acidified vesicular compartments, in lily tepals. MDC-stained structures were observed more frequently in the mesophyll cells of senescing tepals than in pre-senescent tepals. These results suggest that autophagy-like processes are induced as lily tepals senesce. Moreover, the amino acid content gradually increased in tepal mesophyll as the flowers senesced. Such increased amino-acid content was accompanied by a decrease in protein content and an increase in the transcript levels of autophagy-related genes, suggesting the involvement of autophagy-like processes in the production of nitrogenous components resulting from bulk protein degradation. Overall, our data indicated that autophagy-like processes were induced during lily tepal senescence. Further studies on the regulatory mechanisms of autophagy-like processes in ethylene-independent petal senescence may contribute to improvements in flower quality.

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  • Ilya Dovjik, Yosepha Shahak, Avi Sadka
    Article type: Original Articles
    Article ID: SZD-013
    Published: 2025
    Advance online publication: October 19, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Fruit cracking is a fruit peel physiological disorder. In citrus, it typically results in fruit splitting and abscission. Cracking is related to plant water factors and the irrigation regime; heavy or non-regular irrigation is correlated with elevated cracking incidence. In addition, cracking is more common in larger fruit than in smaller ones. Some cultivars are more prone to cracking, suggesting that the phenomenon has a genetic background. However, it has become evident that climatic conditions also affect fruit cracking. As a result, some years are characterized by heavy cracking incidence, and this may be associated with yearly climate variations. Top netting is a useful tool to mitigate microclimates, and it can potentially reduce cracking intensity. We conducted a five-year experiment in a commercial ‘Valencia’ orange orchard, using three different photoselective nets and three distinct irrigation regimes: the recommended level (100%), and two reduced regimes (80% and 60%). Out of the five experimental years, cracking occurred in three years with various intensities. As expected, reduced irrigation in control trees resulted in decreased cracking intensity, and there was a positive relationship between the fraction of cracking and larger fruit size. In netted trees, the cracking intensity was reduced regardless of net color, irrigation regime or fruit size. During the summer, canopy temperature was reduced under the nets, and relative humidity increased. The possible involvement of climatic parameters, modified under the nets, in altering cracking intensity is discussed. Results of this experiment demonstrate the potential of top-netting technology to mitigate cracking intensity in citrus.

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  • Takahiro Sonoda, Priscila Miki Satake, Madoka Sawayanagi, Keiji Ueno, ...
    Article type: Original Articles
    Article ID: QH-157
    Published: 2025
    Advance online publication: October 02, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    In Japan, white asparagus is produced by blanching with soil mounds or film-cover shading methods. However, with either method, white asparagus is produced only in the spring and not during the winter months, when labor and facilities can be more effectively utilized. Recently, a forcing-culture method for green asparagus using polyethylene bags was developed to reduce the workload required in green asparagus production during winter. In this study, we selected a medium composition that reduces bag weight while maximizing yield under a white asparagus forcing culture, as well as cultivars with superior yield and quality. In the first experiment, asparagus was cultivated under forcing culture in polyethylene bags using three different mixed-composition media: lightweight media and horticultural media (1:1, v/v), lightweight media and bark compost (1:1, v/v), and horticultural media and bark compost (1:1, v/v), comprising lightweight media with a bulk density of 0.45 g·mL−1, horticultural media with a bulk density of 0.8–0.9 g·mL−1, and bark compost of 0.4 g·mL−1. The lightest bag (weighing 8.0 kg) contained a combination of lightweight medium and bark compost. No differences were observed between the three combinations in terms of asparagus growth, yield, or spear weight. In the second experiment, the cultivars ‘Taihowase’, No. 056, ‘Suguderu II’, and ‘Welcome’ were grown in a combination (1:1, v/v) of lightweight medium and bark compost. The spear weight of No. 056 was greater than that of ‘Welcome’. No differences in sugar content were observed among the four cultivars. The protodioscin content of ‘Suguderu II’ was higher than that of ‘Taihowase’, No. 056, and ‘Welcome’. These results indicated that forcing culture using bags is practical and that a combination of lightweight medium and bark compost is suitable for this culture method. The best asparagus cultivars among those tested were No. 056, which produced heavy young stems, and ‘Suguderu II’, which developed spears with a high protodioscin content.

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  • Hiroki Taniguchi, Yuki Tsukuda, Ko Motoki, Tanjuro Goto, Yuichi Yoshid ...
    Article type: Original Articles
    Article ID: QH-159
    Published: 2025
    Advance online publication: October 01, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Pollinator insects are required to pollinate flowers in the production of some fruits and vegetables, and strawberries fall into this category. However, the function of pollinators has not been clarified by quantitative metrics such as the duration of pollinator visits needed by flowers. Due to the long activity time of pollinators (approximately 10-h), it is not easy to observe the visitation characteristics manually. Therefore, we developed software for evaluating pollinator performance using two types of artificial intelligence (AI), YOLOv4, which is an object detection AI, and VGG16, which is an image classifier AI. In this study, we used Phaenicia sericata Meigen (green blow fly) as the strawberry pollinator. The software program can automatically estimate the visit duration of a fly on a flower from video clips. First, the position of the flower is identified using YOLO, and the identified location is cropped. Next, the cropped image is classified by VGG16 to determine if the fly is on the flower. Finally, the results are saved in CSV and HTML format. The program processed 10 h of video (collected from 07:00 h to 17:00 h) taken under actual growing conditions to estimate the visit durations of flies on flowers. The recognition accuracy was approximately 97%, with an average difference of 550 s. The software was run on a small computer board (the Jetson Nano), indicating that it can easily be used without a complicated AI configuration. This means that the software can be used immediately by distributing pre-configured disk images. When the software was run on the Jetson Nano, it took approximately 11 min to estimate one day of 2-h video. It is therefore clear that the visit duration of a fly on a flower can be estimated much faster than by manually checking videos. Furthermore, this system can estimate the visit durations of pollinators to other flowers by changing the YOLO and VGG16 model files.

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  • Ryosuke Yamanaka, Takayoshi Yano, Minori Hikawa-Endo, Hisashi Yoshikos ...
    Article type: Original Articles
    Article ID: SZD-015
    Published: 2025
    Advance online publication: September 27, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    To develop a novel highly robust humidification technology that requires minimal adjustment of operational methods, we investigated the vapor pressure deficit (VPD) conditions that cause water stress in strawberry (Fragaria × ananassa Duch.) plants. The relationship between the rate of relative change in fruit-stalk diameter (RCFSDt) and VPD conditions, including VPD and rate of change in VPD (VPD′; hPa·min−1) were analyzed by performing multiple regression. A negative RCFSDt was defined as an indicator that the plant was experiencing water stress. Regression of RCFSDt on VPD and VPD′ revealed that VPD′ greater than 0.069 hPa·min−1 led to negative RCFSDt when VPD was 8.0 hPa or higher. In addition, we investigated whether the rate of change in VPD′ (VPD″; hPa ·min−2) could be used as an indicator to cease humidification, employing both VPD and VPD′. Analysis of the relationship between RCFSDt and VPD″ revealed that even if VPD and VPD′ exceeded 8.0 hPa and 0.069 hPa·min−1, respectively, RCFSDt could not be negative when VPD″ was less than −0.00426 hPa·min−2. We measured the relative change in fruit-stalk diameter (CFSDt) of strawberry under the conditions generated by a novel humidification system. The novel humidification system humidified the air when VPD, VPD′, and VPD″ exceeded each threshold for avoiding the condition, where VPD, VPD′, and VPD″ exceeded 8.0 hPa, 0.069 hPa·min−1, and −0.00426 hPa·min−2, respectively. In practice, there were periods when humidification control was not executed because while VPD exceeded its control threshold, VPD′ and VPD″ were below their respective control thresholds. In addition, the novel humidification system prevented a decrease in CFSDt during the daytime under the non-humidification treatment.

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  • Takuo Fujimoto, Takashi Onozaki
    Article type: Original Articles
    Article ID: QH-149
    Published: 2025
    Advance online publication: September 18, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Dahlia (Dahlia Cav.) is an important ornamental plant used as cut flowers. Recently, we bred the “Eternity series” cultivars with long vase life to overcome the difficulty of long-distance transport due to their short vase life. However, dahlias, including the Eternity series, are ethylene-sensitive, inducing petal abscission within a short period. Therefore, cultivars with long vase life and low degree of abscission were crossed to examine the possibility of producing lines with both traits. The flower life of offspring after treatment with 10 μL·L−1 ethylene (time to ethylene response) was investigated in open-field cultivation during the summer–autumn of 2021. The degree of abscission was classified into three types according to the time to ethylene response and the occurrence of abscission: abscission within four days (high), abscission after four days (mid), and the absence of abscission during senescence (low). We selected 17 of the 105 lines with mid or low degrees of abscission. The degree of abscission of the selected lines was re-evaluated during greenhouse cultivation in the winter–spring of 2021–2022. Three lines (F182-10, F181-14, and F182-17) that showed no petal abscission in the winter–spring were selected. The drawing resistance force of the petals from lines F182-10 and F182-17 was maintained at 1.0 N even during the senescence stage (six days after harvest), which was related to their low degree of abscission. The degree of abscission of lines F182-10, F181-14, and F182-17 was stable during the re-evaluation in summer–autumn of 2023, and their times to ethylene response were 4.8, 5.8, and 4.6 days, respectively. Moreover, the vase lives of lines F182-10 and F182-17 were 5.8 and 5.6 days, respectively, while that of ‘Port Light Pair Beauty’ was 4.4 days. These results suggested that degree of abscission was inherited from ‘Port Light Pair Beauty’, and the vase life was improved after crossing with a cultivar with a long vase life. This is the first report about breeding dahlia with a low degree of abscission, and it indicates the possibility of producing lines with both long vase life and a low degree of abscission.

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  • Takanori Saito, Satoru Kondo, Katsuya Ohkawa, Hitoshi Ohara
    Article type: Invited Review
    Article ID: QH-R003
    Published: 2025
    Advance online publication: August 22, 2024
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Various attempts have been made to use abscisic acid (ABA) as a plant bioregulator (PBR). Recently, a new ABA formulation, produced through microbial fermentation, has been commercialized in Japan as a PBR for improving grape peel color. Nonetheless, the horticultural application of ABA remains limited compared to other plant hormones. Generally, the vital functions of ABA include the regulation of abiotic stress tolerance and plant dormancy via metabolic changes associated with the antioxidant system and the modulation of sugar biosynthesis/translocation, respectively. These metabolic changes are crucial for the quality of fruit, suggesting the potential of ABA for promoting the production of high-quality fruit. In non-climacteric fruit, ABA plays a pivotal role in anthocyanin pigmentation, a significant component of the antioxidant machinery. Studies in grapes and strawberries have shown that the responses to ABA differ depending on the type of ABA agonist used and the specific organs to which it is applied. Herein, the influence of ABA on climacteric fruit exhibiting ethylene-regulated ripening is discussed. ABA-mediated ethylene induction followed by ripening suggests a shared regulatory mechanism that underlies ripening in both climacteric and non-climacteric fruits that involves crosstalk between ABA and ethylene. This review firstly summarizes the historical challenges with ABA and its agonist for application as PBRs and discusses the role of ABA in the ripening of non-climacteric fruit, particularly grapes. Subsequently, the molecular background of ABA in both climacteric and non-climacteric fruit ripening is explained, with a focus on peel coloration, sugar synthesis, and aroma volatile synthesis.

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