The Horticulture Journal
Online ISSN : 2189-0110
Print ISSN : 2189-0102
Volume 87 , Issue 3
Showing 1-16 articles out of 16 articles from the selected issue
REVIEW
  • Chikako Honda, Shigeki Moriya
    Type: Review
    2018 Volume 87 Issue 3 Pages 305-314
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: March 13, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Anthocyanin accumulation is responsible for the red color of the skin and flesh of apple fruits (Malus × domestica Borkh.), and redder fruits are more marketable. Pigmentation in the skin of apple fruit varies among different cultivars and is influenced by environmental factors, including temperature conditions and the level of sunlight irradiation. Because warmer temperatures suppress anthocyanin synthesis in the skin of apple fruit, there are increasing concerns that global warming may be detrimental to fruit pigmentation. Recent molecular studies have revealed that the MdMYB1/10/110a gene, which encodes a transcription factor, plays a critical role in regulating anthocyanin synthesis in both the skin and flesh of apple fruits. A marker-assisted selection process has been developed to identify MdMYB1 genotypes and predict those fruits that will develop redder skin. These apples may be better adapted to a warmer global climate. The application of hormones can also increase the level of pigmentation in fruit skin, and plant growth regulators such as ethylene and jasmonate are commercially available. The mechanisms that regulate anthocyanin biosynthesis in the flesh of red-fleshed apple fruit appear to partially differ from those that function in the skin of red-skinned fruit. In the flesh of red-fleshed fruit, the pigment accumulates under dark conditions, whereas no anthocyanin is synthesized in the skin of bagged apple fruit. Conversely, in both red-skinned and red-fleshed apple fruits, warmer temperatures inhibit anthocyanin accumulation. Further studies on the regulation of anthocyanin synthesis in the flesh of red-fleshed apple fruit are necessary.

ORIGINAL ARTICLES
  • Soichiro Nishiyama, Noriyuki Onoue, Atsushi Kono, Akihiko Sato, Koichi ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 315-323
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: February 01, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Persimmon (Diospyros kaki) is a tree crop species that originated in East Asia, consists mainly of hexaploid individuals (2n = 6x = 90) with some nonaploid individuals. One of the unique characteristics of persimmon is the continuous accumulation of proanthocyanidins (PAs) in its fruit until the middle of fruit development, resulting in a strong astringent taste even at commercial fruit maturity. Among persimmon cultivars, pollination-constant and non-astringent (PCNA) types cease PA accumulation in early fruit development and become non-astringent at commercial maturity. PCNA is an allelic trait to non-PCNA and is controlled by a single locus called the ASTRINGENCY (AST) locus. Previous segregation analyses indicated that the AST locus shows hexasomic inheritance; a recessive allele, ast, at this locus confers PCNA. Here, we report a shuttle mapping approach to delimit the AST locus region in the hexaploid persimmon genome by using D. lotus, a diploid relative of D. kaki, as a reference. A D. lotus F1 population of 333 individuals and 296 D. kaki siblings segregating for the PCNA trait were used to map the AST region using haplotype-specific markers covering the AST region. This indicated that the AST locus is syntenic to an approximately 915-kb region of the D. lotus genome. In this 915-kb region, we found several candidates for AST that were revealed from the fruit transcriptome of a population segregating for the PCNA trait. These results could provide important clues for the isolation of AST in hexaploid persimmon.

  • Yoshitaka Kawai, Tadashi Baba, Mika Yoshida, Josephine U. Agravante, D ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 324-328
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: February 08, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    In harvested calamondin fruit, the effects of benzyladenine (BA) and light on the rind color and fruit quality were investigated. BA application delayed degreening of the calamondin fruit in both light and dark conditions. At 5 days, BA application had no influence on total soluble solids (TSS), titratable acid (TA), sugar contents, ascorbic acid (AA), and organic acid in the fruit juice and at 9 days, only AA content has decreased in BA-treated fruits. Light promoted quick degreening of calamondin fruit, whereas in the dark, degreening had proceeded very little in un-treated fruit at 9 days. Light did not influence fruit quality at 5 days either. However, light influenced the sugar content, especially increasing glucose and total sugar, as well as AA content in fruit at 9 days. Concerning the AA content in calamondin fruit, BA decreased and light increased it. These results indicated that BA treatment after harvest and maintaining fruit in the dark are sufficient to retain the green rind color of harvested calamondin fruit without affecting fruit quality, except for AA content.

  • Manato Ohishi-Yamazaki, Miho Watanabe, Ai Nakanishi, Jingai Che, Naomi ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 329-339
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: March 13, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    We attempted to shorten the juvenile phase of southern highbush blueberries by using controlled rooms under artificial light. Seeds were extracted from fresh fruits and sowed in the Woody Plant Medium (WPM) immediately after harvest. When these seeds were irradiated with red LED, their germination rate was over 80% by the 35 days after sowing. The seedlings in the controlled room continued to grow without entering the dormant phase. Especially, maximum growth was observed under the long-day condition of 12-h light. Even under the short-day condition of 8-h light, increased growth was observed when grown at a high light intensity (400 μmol·m−2·s−1). For the seedlings that were moved from the long-day controlled room to the short-day controlled room after 10 months, the ‘Misty’ seedlings flowered within 327 days after sowing while the ‘Sharpblue’ seedlings flowered within 357 days after sowing. Furthermore, when cultivated under the short-day condition at 400 μmol·m−2·s−1 for the entire length of the experiment, the flowering of ‘Misty’ seedlings was observed within 300 days after sowing. The seedlings maintained under the short day condition of high light intensity flowered earlier than seedlings moved from the long-day controlled room to the short-day controlled room. Thus, southern highbush blueberries were successfully induced to flower in less than a year from seed planting, using a combination of techniques to promote germination and control the growth environment conditions in a controlled room.

  • Masashi Yamamoto, Yuta Natori, Kei Kawai
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 340-348
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: March 13, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    An investigation of local citrus genetic resources grown on the Chuuk Islands of the Federated States of Micronesia was conducted in August 2013. A total of 21 accessions were examined. According to the morphological traits, ten, four, four, two, and one accession resembled lime (local name “Nayimis”), sour orange (“Kurukur”), calamondin (“Tangerin” and “Gunkan”), sweet orange (“Kurukur” and “American Kurukur”), and pummelo (“Kurukur”), respectively. Next, cleaved amplified polymorphic sequence (CAPS) analysis was conducted. Then, precise accession identification was made based on the results of CAPS analysis in conjunction with morphological traits. “Nayimis” accessions were classified into at least two types. Genotypes of “Nayimis” type 1 were identical to those of Mexican lime. A genetic influence from mandarin was detected in “Nayimis” type 2. Although the morphological traits of all “Kurukur” sour orange types were similar, their diversity was revealed by CAPS analysis. The genotype of one “Kurukur” accession was identical to that of sour orange. Genotypes of the sweet orange-type “Kurukur” and “American Kurukur” were different. The types of “American Kurukur” and sweet orange were the same. Pummelo-type “Kurukur” was considered to be true pummelo based on the results of morphological and molecular markers. Morphologically, the calamondin-like accessions “Tangerin” and “Gunkan” showed the same genotype combinations on CAPS analysis. These genotypes were identical to those of calamondin used as a control. The combined results of morphological and molecular markers offer valuable information for the identification of citrus genetic resources on the Chuuk Islands.

  • Yu Sung, Shih-Wen Chen
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 349-355
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: March 20, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Currently, biofortification breeding programs are being conducted to increase the selenium (Se) content of crops. Se is an element essential to humans and is mostly acquired via consumption of vegetables. However, the effects of Se on the main plant metabolisms such as nitrogen metabolism are unclear. The main objective of this study was to determine the effect of the application of different concentrations of Se (10, 20, and 30 μM) as Na2SeO4 on nitrogen metabolism in Pak-choi grown hydroponically. Supplemental Se increased all enzyme activities analyzed, including nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT). In 20-μM Se treatment of two cultivars, the fresh weight was significantly increased and the foliar NO3 content was significantly decreased. Compared to the control, the data on Se treatments showed stronger activations of NR, GS, and GOGAT, as well as greater concentrations of total ammonium, amino acid, and protein, and a higher nitrogen use efficiency, resulting in increased biomass production. This suggests the mechanism of Se applied to Pak-choi to decrease NO3 content was due to increasing nitrogen metabolism and protein synthesis to biomass.

  • Takanori Masukawa, Masayuki Kadowaki, Toshikazu Matsumoto, Akira Nakat ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 356-363
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: January 06, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Purple and red colored root characteristics were introduced to a local pungent radish “Izumo orochi daikon” ‘Susanoo’, and several characteristics including food functional components were evaluated. The root and leaf phenotype, the pigment composition, the isothiocyanate and soluble solids contents, and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in the root were investigated. These characteristics were compared between the mass selection breeding lines of purple, red roots and their parent cultivars. Although one-third of individuals in the M6 and M7 were non colored, the colored root characteristics was introduced into ‘Susanoo’. The main anthocyanins in the deep reddish purple colored purple root lines were acylated cyanidin 3-sophoroside-5-glucosides, and those in the vivid purplish red colored red root lines were acylated pelargonidin 3-sophoroside-5-glucosides, which corresponded to the main anthocyanins in their respective colored root parental cultivars. The isothiocyanate contents in the purple and red root lines were almost the same as that in ‘Susanoo’. The DPPH radical scavenging activity of the purple and red root lines was almost two times higher than that of ‘Susanoo’. These results showed that the food functionality was enhanced by introduction of a colored root characteristic in ‘Susanoo’.

  • Sota Koeda, Kanami Homma, Yuri Tanaka, Daiki Onizaki, Elly Kesumawati, ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 364-371
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: December 20, 2017
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Indonesia is one of the world’s largest fresh pepper (Capsicum spp.) fruit-producing countries, and hot peppers are essential spices in Indonesian cuisine. During the last two decades, begomovirus, which is transmitted by the whitefly, Bemisia tabaci (Gennadius), and causes pepper yellow leaf curl disease, began to cause a huge economic loss by damaging pepper plants in Indonesia. In the present study, a highly efficient inoculation method was established for Pepper yellow leaf curl Indonesia virus (PepYLCIV), the most infectious bipartite begomovirus in pepper plants cultivated in North Sumatra, by combining agroinoculation and subsequent grafting. Partial tandem repeats of PepYLCIV DNA A and B were constructed and cloned into a binary pGreenII vector, and their infectivity was tested. Co-inoculation of Nicotiana benthamiana L. and Solanum lycopersicum L. ‘Momotaro’ with PepYLCIV DNA A and DNA B resulted in the production of typical begomoviral symptoms. Both the injection of the cotyledons with cultured agrobacteria and the inoculation of the hypocotyl with agrobacterial colonies induced viral symptoms in pepper No. 218 (C. annuum L.) seedlings in approximately 55–75%. When agroinoculated symptomatic No. 218 was grafted onto an uninfected ‘Takanotsume’ (C. annuum), all newly elongated shoots from the rootstock of ‘Takanotsume’ produced typical begomoviral symptoms. Agroinoculation combined with subsequent grafting provides a highly efficient method for introducing PepYLCIV into pepper plants.

  • Moalla Rached, Baldet Pierre, Gibon Yves, Chiaki Matsukura, Toru Ariiz ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 372-381
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: February 16, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Calcium is widely accepted as the main factor responsible for blossom-end rot (BER) appearance in tomato (Solanum lycopersicum L.) fruit. However, reactive oxygen species (ROS), which can damage plant tissues have also been proposed to initiate BER appearance in tomatoes and other fruit-bearing vegetables. Ascorbate, the major antioxidant in tomato fruit, is generally lower during green fruit development, which corresponds to the stage of BER appearance. Accordingly, one hypothesis is that tomato cultivars with a lower susceptibility to BER under salt stress have higher ascorbate contents and thus better control of ROS levels. In this study, to clarify the relationship between BER incidence and oxidative stress, two BER resistant cultivars, ‘Managua RZ’ and ‘House Momotaro’ and one BER-susceptible cultivar ‘Reiyoh’, were cultivated under salinity or standard nutrient solution (control) conditions. Calcium, potassium, magnesium, total hydro-soluble antioxidants, and ascorbate concentrations were measured in the distal pericarp 1 to 2 days prior to symptom appearance and during symptom appearance in healthy and affected fruits. When salt stress was applied, only BER-resistant cultivars showed a significant increase in ascorbate contents prior to BER appearance as compared with their levels under the control condition. In contrast, pre-BER Ca2+ concentrations did not associate with the BER susceptibility of each cultivar. Interestingly, ‘Reiyoh’ showed much higher K+/Ca2+ and (K++Mg2+)/Ca2+ ratios than the two other cultivars in healthy fruits due to a strong tendency towards lowered Ca2+ concentrations. A similar tendency was also observed in apple “bitter pit”. The ability to increase the fruit antioxidant capacity and maintain mineral balance under salt stress conditions may explain the resistance to BER development in highly resistant cultivars, probably by the avoidance of oxidative-induced cell necrosis and stabilization of the cell membranes, respectively.

  • Ryuichi Suwa, Hironori Tajima, Shinichi Gima, Naoko Uehara, Kenta Wata ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 382-388
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: March 13, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    In Japan, several plant species have high commercial value because of their functional properties. In this study, we aimed to investigate the effects of soil type (red, dark-red, and gray soil) and growth stage (vegetative and reproductive) on the growth and polyphenol production (chlorogenic acid, rutin, hesperidin, and diosmin) of P. japonicum. Plants grown in gray soil had the heaviest dry weight, followed by those grown in dark-red soil. Flowering plants grown in gray soil had a polyphenol concentration lower than those grown in the other two soil types. However, differences in the concentration of polyphenols were even larger between the growth stages. During the flowering period, the concentration of polyphenols sharply increased in the stems. Additionally, the flowers contained relatively similar amounts of polyphenols to stems and leaves, accounting for approximately 1/4–1/2 of the net amount in the plant.

  • Yong Ha Rhie, Seonghwan Kang, Dong Chan Kim, Jongyun Kim
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 389-394
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: December 27, 2017
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Improving water use and nutrient efficiency can play a pivotal role in ensuring sustainable production of horticultural crops. This study aimed to investigate the optimum moisture level that best management practices need to ensure for high-quality garden mum production, and also determine the feasibility of using a soil moisture sensor-based automated fertigation system for water and nutrient management for high-quality garden mum production. We used 20 5TE (Decagon Devices, Pullman, WA, USA) sensors to monitor and control fertigation based either on the substrate volumetric water content (θ, v/v) at 0.25, 0.35, 0.45, and 0.55 m3·m−3, or conventional greenhouse management culture practices. At harvest, most vegetative growth parameters were not significantly different across the treatments, but the leaf relative water content of plants under the 0.25 m3·m−3 treatment was lower than that of plants under other treatments, indicating that the plants were drought stressed. Although flower diameters and peduncle lengths were similar across the treatments, the number of flowers of plants under the 0.25 and 0.35 m3·m−3 treatments were 25–37% less compared to that of plants under the 0.45 and 0.55 m3·m−3 treatments, and the conventional culture practice, which suggested decreased quality of garden mums under water stress. Water savings without a decrease in product quality by adopting the automated fertigation system with the threshold θ values of 0.45 and 0.55 m3·m−3 were 34.2% and 42.7% of the conventional cultural practice, respectively. The soil moisture sensor-based automated fertigation system can therefore save a considerable amount of water and fertilizer and ensure efficient water and nutrient management for practical production of high-quality garden mums.

  • Kyoko Kawakatsu, Taro Harada, Ayuko Ushio, Mitsuru Dozono, Naoko Fukut ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 395-405
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: February 17, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    The number of petals in a flower is one of the most important appearance qualities of ornamental flowers. In Eustoma, the number of petals fluctuates significantly and little is known about how it is controlled. We investigated the cultivating conditions that affect the number of petals in double flowers and tried to develop a technique for growing splendid corolla. High temperature in the reproductive phase reduces the number of petals. The transient treatment of high temperature just prior to the petal initiation stage is sufficient to control such a reduction. The measurement of flower bud growth showed that one week of temperature treatment is necessary to control the number of petals in a flower. The integration of our results demonstrated that both daytime and nighttime temperatures affected the number of petals and that the number of petals was clearly correlated with average daily temperature within the range of 20°C < x < 25°C. This phenomenon applies to various cultivars in Eustoma grandiflorum. We propose the greenhouse conditions necessary to achieve both high quality flowers and reduced energy consumption by considering the temperature and stages of flower development.

  • Kenji Yamane, Kitaro Sumida, Yuri Terui, Nagisa Kojima, Chairat Burana ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 406-412
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: February 08, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Temperature regimes that cause malformed flowers were examined and histological observation was carried out at the developmental stage of flowers by using mutants of the potted carnation (Dianthus caryophyllus L.) ‘Cherie’ producing malformed flowers according to cultivation season. Plants of normal (WT) and malformed (mlf) lines were grown under several temperature regimes. All WT plants produced normal flowers, whereas mlf lines showed a variety of malformed floral phenotypes, including phyllody-like proliferated sepaloids, proliferated petaloids, proliferated pistillodes with or without petals, secondary flower formation, and a flattened receptacle. In Experiment 1, mlf plants produced no malformed flowers when grown under constant 26°C, whereas 34.2% of mlf plants produced malformed flowers at 14–16/12°C (day/night, natural light). Malformation frequency was slightly lower at a night temperature of 5°C compared with 14–16/12°C. When malformed mlf plants were transferred from 17/5°C to 23/18°C, flower malformation was alleviated. Conversely, when mlf plants grown under constant 26°C with a normal phenotype were transferred to 17/12°C, flower malformation was induced. Thus, flower malformation was reversible depending on the temperature regime. In Experiment 2, 92.2% of mlf plants produced malformed flowers under constant 15°C, whereas 3.1% and 1.3% showed flower malformation when grown under constant 20°C and 25/20°C, respectively. These findings suggested that the threshold for flower malformation is between 15°C and 20°C. Observation of shoot apices by optical microscopy and scanning electron microscopy revealed morphological differences between WT and mlf after sepal formation. Petal primordia were not visible in mlf plants at 15°C, although petal primordia were initiated in WT. After this stage, flower malformations observed in mlf included undeveloped petals, undeveloped or irregularly developed stamens, secondary flower primordia formation, and completely irregular arrangement of undeveloped flower organs. No phytoplasma was detected by PCR, indicating that it could not be the causal agent of the abnormal phenotypes. This is the first report of mutant flower phenotypes dependent on temperature and induced by only a 5°C difference within optimal growing-temperature regimes in carnations.

  • Keigo Fukushima, Shinji Kajihara, Satoshi Ishikura, Noritoshi Katsutan ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 413-420
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: February 08, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    This study was initiated to investigate the effects of wet treatment at 10°C (WT10°C) and subsequent re-drying treatment (RDT) on the germination and growth of Eustoma grandiflorum seeds. Both treatments, WT10°C and RDT, were applied at 10°C under dark conditions. In all the experiments, ‘King of Snow’, which is one of the major Eustoma cultivars in Japan, was used. When the total number of days exposed to WT10°C and RDT was set to 35 days, the prevention of rosettes and the promotion of growth were dependent on the number of days of WT10°C, and these effects were maintained after RDT. When RDT was applied to the seeds after WT10°C for 35 days, the growth promotion due to WT10°C was maintained regardless of the length of re-drying time from 7 to 28 days; however, the germination rate decreased with RDT. On the other hand, applying RDT after WT10°C for 14 days had no effect on the germination rate; however, the growth promotion was insufficient compared with WT10°C for 28 days. This problem was solved by carrying out a further 14 days of WT10°C after RDT. When the seeds were exposed to WT10°C for 14 days, then re-dried for 7 days, and exposed to WT10°C for a further 14 days, the same growth promotion was achieved as for seeds exposed to WT10°C for 28 days continuously. The above results suggest that the promotion of growth depends on the total number of days of WT10°C regardless of whether these days are continuous or not. Moreover, the growth promotion was maintained after RDT. The results also suggest the possibility that when both the processes of WT10°C and the RDT are carried out by seed companies, growers who have no cooling equipment can produce cut flowers using seedlings grown in the high-temperature season.

  • Oscar Witere Mitalo, William Olubero Asiche, Yuka Kasahara, Yasuaki To ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 421-429
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: April 19, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    ‘Rainbow Red’ kiwifruit have been reported to gradually ripen during low temperature storage and on the vine in the absence of detectable ethylene. This study was conducted to compare the expression of ripening-related genes during storage at different temperatures and on the vine. Fruit at 5°C and 10°C ripened faster to eating quality within four weeks accompanied with increased expression of ripening-related genes: AcACO3, AcXET2, AcEXP1, AcPG, AcPMEi, AcSUS, AcβAMY1, AcβAMY2, AcGA2ox2, AcNAC3, AcNAC4, and AcMADS2. Fruit at 15°C required a longer period of eight weeks to attain eating quality in concurrence with delayed accumulation of the ripening-related genes. Fruit at 22°C ripened at the slowest rate and did not attain eating quality even after eight weeks, with very minimal accumulation of ripening-related genes. On-vine ripening occurred slowly at the early stages when the average field temperature was ~20°C, but the rate increased as the temperature dropped to ≤15°C accompanied by increased expression of ripening-related genes. These results indicate that both ripening on-vine and during low temperature storage are modulated by low temperature independent of ethylene.

  • Yusuke Kamiyoshihara, Shinji Mizuno, Mirai Azuma, Fumika Miyohashi, Ma ...
    Type: Original Articles
    2018 Volume 87 Issue 3 Pages 430-435
    Published: 2018
    Released: July 28, 2018
    [Advance publication] Released: January 26, 2018
    JOURNALS OPEN ACCESS FULL-TEXT HTML

    Avocado fruit ripen with ethylene production after harvest and the flesh becomes soft and edible due to degradation of cell wall polysaccharides during ripening. α-l-Arabinofuranosidase is a hydrolytic enzyme known to digest arabinose-containing cell wall polysaccharides. It has been shown that its activity increased with fruit ripening. However, our previous study showed that an α-l-arabinofuranosidase gene (PaArf/Xyl3A) is expressed in the avocado fruit before ethylene production. In addition, the transcripts were detected in some organs in which the level of ethylene was extremely low. These results indicate that the gene expression is independent of ethylene. In the present study, we carried out immunoblot analyses of α-l-arabinofuranosidase at the protein level. Using a polyclonal antibody raised against Japanese pear α-l-arabinofuranosidase, two α-l-arabinofuranosidase proteins with molecular masses of 72 kDa and 68 kDa, presumably belonging to glycoside hydrolase family 3, were detected in ripening avocado fruit. The protein levels in ethylene or 1-methylcyclopropene (1-MCP)-treated fruits were examined and the results indicated that the two proteins responded to ethylene in opposite ways; the 68 kDa protein showed a temporary accumulation, whereas the 72 kDa protein exhibited dissipation possibly caused by a loss of stability. The total enzyme activity of α-l-arabinofuranosidase was elevated faster in the ethylene-treated fruit throughout ripening and was slower in the 1-MCP-treated fruit, suggesting the existence of another α-l-arabinofuranosidase, which did not cross-react with the antibody and was positively regulated by ethylene, in ripening avocado fruit.

feedback
Top