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Volume 86 , Issue 2
Showing 1-16 articles out of 16 articles from the selected issue
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ORIGINAL ARTICLES
  • Yoshito Sasaki, Yasuo Ishii, Hironobu Abe, Katsuaki Mitachi, Takayoshi ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 139-144
    Released: April 25, 2017
    [Advance publication] Released: August 11, 2016
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    To examine the translocation of radiocesium scattered by the Fukushima Daiichi nuclear power plant accident that occurred in March 2011 to the Japanese chestnut, we investigated the autoradiography and radiocesium concentration in each part of Japanese chestnuts. The Japanese chestnut fruit has a thin skin between the kernel (cotyledons) and shell; the kernel of the fruit is edible. The 137Cs concentration in each part of the fruit was found to be almost the same at about 1.0 × 104 Bq·kg−1 DW, as well as leaves. The radiocesium concentration in chestnut weevil larvae found on the fruit was approximately one-seventh of that in the kernel.

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  • Fumio Fukuda, Yuki Tomita, Yukihito Aishima, Kumiko Koumoto, Yuichiro ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 145-150
    Released: April 25, 2017
    [Advance publication] Released: August 18, 2016
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    Reddish pulp is one of the most serious disorders in peach production, in which originally white flesh undergoes pink to red discoloration with the development of a mealy texture. In order to clarify the relationship between the incidence of reddish pulp and flowering date, the occurrence of reddish pulp was investigated in ‘Benishimizu’ and ‘Shimizu Hakuto’ fruit with different flowering dates for three seasons. In both cultivars, the percentage of fruit with reddish pulp was higher in early flowering fruit than late flowering fruit in all three seasons. Analysis of pectin and boron contents in immature fruit sampled from June 23 to July 8, prior to observing the symptoms of reddish pulp, showed no statistically significant differences in pectin content between early and late flowering fruit. On the other hand, the boron content in flesh was significantly lower in early flowering fruit that bloomed on April 1 than in late flowering fruit that bloomed on April 11 in ‘Benishimizu’. In addition, a significantly higher total polyphenol content, which is one of the characteristics of reddish pulp, was found in early flowering fruit. The results indicate that the flowering date has a large impact on the incidence of reddish pulp, and the disorder is more prevalent in early than late flowering fruit. The possible relationships among the development of reddish pulp, boron deficiency, pectin content, and increase in total polyphenol content are discussed.

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  • Naftali Zur, Lyudmila Shlizerman, Giora Ben-Ari, Avi Sadka
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 151-158
    Released: April 25, 2017
    [Advance publication] Released: July 12, 2016
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    Fruit splitting is a preharvest physiological disorder that occurs in many commercially important fruit species, including some citrus cultivars such as Navel oranges, Valencia oranges, and some mandarins. The phenomenon is affected by both genetic background and environmental conditions, causing heavy fruit loss in splitting-prone cultivars in some years. For instance, high levels of irrigation usually enhance splitting incidence. The phenomenon initiates at the end of the summer, toward fruit maturation, and to date, there is no way to predict splitting incidence. Here, we tested the ability of nondestructive magnetic resonance imaging (MRI), which does not alter the dimensions of the internal fruit tissues, to predict splitting incidence in ‘Nova’ mandarin fruit populations of trees subjected to two levels of irrigation (low and high). Samples, collected about two months prior to splitting appearance, were sorted by their internal tissues dimensions. Among all measured tissues, sorted navel dimensions showed the best correlation with splitting incidence. This was determined by dividing the MRI-sampled fruits into two populations, according to the actual splitting incidence, as calculated at the end of the season. Prediction of the splitting percentage in the low irrigation fruit population was than possible in the high irrigation fruit population, and vice versa. These results demonstrated the power of MRI to predict splitting probability as early as 2 months before split fruit are found. In addition to its potential practical application, the ability to predict splitting probability in a given fruit population could help elucidate the mechanism underlying the disorder.

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  • Shigeki Moriya, Miyuki Kunihisa, Kazuma Okada, Hiroshi Iwanami, Hiroyo ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 159-170
    Released: April 25, 2017
    [Advance publication] Released: July 23, 2016
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    During apple (Malus × domestica Borkh.) storage, a loss in fruit firmness can occur. This is frequently associated with mealiness, an undesirable trait. There have been studies, such as phenotypic analyses and transcriptomics, as well as others employing a transgenic approach, focusing on this trait. Certain genetic approaches, such as quantitative trait loci (QTL) approach, however, have not been attempted. In this study, to identify and characterize QTLs controlling flesh mealiness and to investigate their application in apple breeding, we performed classical QTL mapping based on a bi-parental population and a genome-wide association study (GWAS) of mealiness. Phenotypic data for mealiness allowed us to identify two QTLs in the bi-parental family located on linkage group 10. The GWAS discovered significant marker-trait associations on chromosomes 2, 9, and 10. The MdPG1 locus, located on chromosome 10, was identified as the locus with the strongest significance by both QTL mapping and GWAS, suggesting its primary contribution to flesh mealiness. Using a tri-allelic simple sequence repeat marker, Md-PG1SSR10kd, 10 kb downstream of the MdPG1 coding sequence, we divided apple accessions into six groups based on their genotypes. Among the six groups, the Md-PG1SSR10kd genotype “2/2” had the least mealy phenotype.

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  • Mei Gao-Takai, Ayako Katayama-Ikegami, Shinichi Nakano, Kenichi Matsud ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 171-182
    Released: April 25, 2017
    [Advance publication] Released: September 17, 2016
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    The growth and berry quality of ‘Ruby Roman’ (Vitis labruscana) grapevines grafted on two species of rootstock, ‘Kober 5BB’ [‘5BB(2×)’] (V. berlandieri × V. riparia, a semi-dwarf rootstock) and ‘Hybrid Franc’ [‘HF(2×)’] (V. rupestris × V. vinifera, a vigorous rootstock), and their colchicine-induced autotetraploids [‘5BB(4×)’ and ‘HF(4×)’] were investigated through 2 years of pot cultivation followed by 2 years of ground cultivation. During the nursery stage, the survival rate and root and shoot growth of the grafted cuttings in the two diploid rootstocks were obviously greater than in their corresponding tetraploids. During subsequent cultivation in pots and in the ground, the grapevines grafted on ‘5BB(4×)’ had less shoot growth (weight and length), shorter internode length, and in some cases smaller stem diameter than those grafted on ‘5BB(2×)’. However, in contrast with ‘5BB’, there was no significant difference in total vine growth between ‘HF(2×)’ and ‘HF(4×)’ during pot cultivation, and the total shoot length and weight in the ‘HF(4×)’ grapevine was greater than in ‘HF(2×)’ during ground cultivation in 2014. After 2 years of pot cultivation, the root growth of the ‘HF’ (diploid and tetraploid) rootstocks was more vigorous than that of the ‘5BB’ (diploid and tetraploid) rootstocks. In addition, the proportions of the thin roots (diameters <1 mm) in the two diploid rootstocks [‘5BB(2×)’ and ‘HF(2×)’] were greater than those in the two tetraploid rootstocks [‘5BB(4×)’ and ‘HF(4×)’]. In contrast, the proportions of the thick roots (diameters 1–2 mm, 2–5 mm, and >5 mm) in the two diploid rootstocks were less than those in the two tetraploid rootstocks. Furthermore, the berries of ‘Ruby Roman’ harvested from the grapevines grafted on ‘5BB(4×)’ exhibited a much deeper skin coloration than those harvested from the other grapevines.

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  • Nobuhiro Kotoda, Satoshi Matsuo, Ichiro Honda, Kanako Yano, Tokurou Sh ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 183-193
    Released: April 25, 2017
    [Advance publication] Released: September 27, 2016
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    Gibberellins (GAs) are involved in many aspects of plant growth and development in higher plants. In this study, we aimed to characterize Satsuma mandarin (Citrus unshiu Marc.) GA 2-oxidase genes encoding enzymes with GA inactivation activity because the accumulation of active GAs is regulated by the balance between their synthesis and inactivation. We showed that CuGA2ox4, CuGA2ox2/3, and CuGA2ox8 were differentially expressed in various tissues in Satsuma mandarin and that these genes functioned like GA 2-oxidase genes in transgenic Arabidopsis. The expression pattern of CuGA2ox4 resembled that of CuGA20ox1, which was reported previously as a Satsuma mandarin GA 20-oxidase gene, in the reproductive tissues of the adult trees in that both genes were expressed in juice sacs in November and December and peel in December, suggesting that CuGA2ox4 and CuGA20ox1 act in concert to regulate the accumulation of active GAs in fruit at the maturing stage. On the other hand, CuGA2ox2/3 and CuGA2ox8 were more highly expressed in seeds and flower buds, respectively. Further study of GA biosynthetic genes, including GA 2-oxidase genes, would provide insight into the mechanism of flowering, fruit development, seedlessness, biennial bearing, and peel puffins of citrus such as Satsuma mandarin.

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  • Atsushi Shimada, Tatsuya Kubo, Shigeto Tominaga, Masashi Yamamoto
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 194-199
    Released: April 25, 2017
    [Advance publication] Released: September 27, 2016
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    The effects of temperature and light on photosynthetic, chlorophyll fluorescence characteristics under high temperature in the passion fruits ‘Summer Queen’ (P. edulis × P. edulis f. flavicarpa) and ‘Ruby Star’ (P. edulis × P. edulis f. flavicarpa) were examined. Photosynthetic rates of both cultivars markedly and linearly increased up to 300 μmol·m−2·s−1, and less markedly increased from 300 to 1500 μmol·m−2·s−1 under several light conditions. Their light saturation points were recorded at around 1200 μmol·m−2·s−1 photosynthetic photon flux densities (PPFD). Regarding the relationship between temperature and photosynthesis, the maximum value of the apparent photosynthetic rate of ‘Summer Queen’ was observed at 30°C, and it was lower at both lower and higher temperatures. In ‘Ruby Star’, on the other hand, the maximum value was observed at 20 to 30°C, and this decreased at 35 and 40°C. The gross photosynthetic rate of ‘Summer Queen’ decreased over 30°C whereas in ‘Ruby Star’, it decreased to a lesser extent. The transpiration rate of ‘Ruby Star’ was higher than that of ‘Summer Queen’ at 40°C. Dark respiration increased from 20 to 40°C in both cultivars. Concerning chlorophyll fluorescence characteristics, ‘Summer Queen’ showed high-temperature injury at 40°C and all parameters were significantly decreased at 45°C. On the other hand, Fv/Fm showed only a slight decrease at 45°C in ‘Ruby Star’. These results indicate that ‘Summer Queen’ is susceptible to heat stress and that the range of its optimal temperature for photosynthesis is lower than ‘Ruby Star’.

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  • Atsushi Imai, Takeshi Kuniga, Terutaka Yoshioka, Keisuke Nonaka, Nobuh ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 200-207
    Released: April 25, 2017
    [Advance publication] Released: September 24, 2016
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    We analyzed the pedigree records (1995–2010) of the Kuchinotsu Citrus Breeding Program (KCBP) at the National Institute of Fruit Tree Science (NIFTS) in Japan, abbreviated as NIFTS-KCBP, to reveal the genetic background and current status of inbreeding and genetic uniformity of the parental cultivars/genotypes and their F1 breeding progenies. The founding genotypes mostly used for crossing in NIFTS-KCBP were satsuma mandarin (Citrus unshiu Marcow.), sweet orange (C. sinensis [L.] Osbeck), king mandarin (C. nobilis Lour.), clementine (C. clementina hort. ex Tanaka), mediterranean mandarin (C. deliciosa Ten.), dancy tangerine (C. tangerina hort. ex Tanaka), and ponkan (C. reticulata Blanco). The intensive use of these seven genotypes and their progenies as crossed parents has led to a high degree of inbreeding in the breeding population. Moreover, these seven genotypes have dominated about 80% of the genetic composition of the breeding population. Although further studies are needed to reveal the influence of inbreeding and genetic uniformity on agronomically important traits, these data offer useful information for the selection of cross combinations and breeding strategies in the ongoing NIFTS citrus breeding program, Japan.

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  • Keisuke Nonaka, Hiroshi Fujii, Masayuki Kita, Takehiko Shimada, Tomoko ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 208-221
    Released: April 25, 2017
    [Advance publication] Released: October 04, 2016
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    To protect the rights of breeders of the major citrus cultivars developed under breeding programs by the national institute of Japan, we developed a method of cultivar identification based on cleaved amplified polymorphic sequence (CAPS) markers, and used it to evaluate their identity and parentage. We selected 19 CAPS markers that had a single-locus origin and moderate polymorphism, and used them to construct genotyping data for 59 citrus cultivars (including American accessions), local varieties, and selections. Of the 19 CAPS markers, 8 were sufficient to discriminate among all accessions except ‘Mato’ buntan (Citrus grandis Osbeck) and ‘Hirado’ buntan (Citrus grandis Osbeck). Among the 33 Japanese cultivars, the parentage of 30 agreed with that reported, but ‘Setoka’, ‘Southern Red’, and ‘Reikou’ had discrepancies at one or more loci. Using 15 to 18 CAPS markers to validate the putative parentage revealed that the seed parent of ‘Setoka’ was ‘KyEn No. 4’, not ‘Tsunonozomi’, and the pollen parent of ‘Southern Red’ was ‘Osceola’, not ponkan (C. reticulate Blanco). The seed parent of ‘Reikou’ remains unknown.

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  • Miriam Valle Arizaga, Oscar Fabián Villalobos Navarro, Carlos Roman Ca ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 222-228
    Released: April 25, 2017
    [Advance publication] Released: July 16, 2016
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    We modified the D cryo-plate protocol by paper mounting to the cryo-plate with alginate gel and shoot tips, and cryopreserved shoot tips of 13 potato genotypes (potato genetic resources in Mexico) using the revised and optimized D cryo-plate protocol. There were no significant differences in regrowth of cryopreserved shoot tips by addition of the paper mounting step to the base D cryo-plate protocol, besides a reduction in dropping shoot tips in steps during the whole procedure. Some steps of revised D cryo-plate protocol were optimized or reconfirmed, and the effect of optimizations such as cold-hardening, loading solution treatment, and post-rewarming treatment on the regeneration of shoot tips was studied. This optimized protocol was successfully applied to ‘B-71-240-2’ and 12 additional potato genotypes, resulting in 70.0%–93.3% regrowth with an average of 82.8% and stable storage for 1 year. When introducing new cryopreservation techniques, modification and optimization of the method are required to adjust to each laboratory’s circumstances. This optimized D cryo-plate method will facilitate cryobanking of potato and other plant genetic resources in Mexico for long-term preservation in a genebank.

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  • Geng Zhang, Masahumi Johkan, Masaaki Hohjo, Satoru Tsukagoshi, Toru Ma ...
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 229-237
    Released: April 25, 2017
    [Advance publication] Released: September 08, 2016
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    Chronic kidney disease has become a major public health problem worldwide. The aim of this study was to investigate the differences in plant growth and photosynthesis among three lettuce (Lactuca sativa) types with different morphological characteristics under low potassium conditions, providing information for improving the method of low-potassium lettuce culture. Lettuce was hydroponically grown in half-strength Enshi formula nutrient solution containing 4, 2, or 1 me·L−1 K+. The plant yield and relative growth rates (RGR) of all three lettuce types were lowest under a treatment with 1 me·L−1 K+. In green leaf lettuce, reductions in both the net assimilate rate (NAR) and leaf area ratio (LAR) led to a decline in RGR. In Boston lettuce and romaine lettuce, the reduction of RGR was mainly due to a reduction in LAR, and to a lesser extent caused by NAR. Reduced potassium in the nutrient solution had a greater effect on mature leaves than on newly expanded leaves for all three lettuce types. In green leaf lettuce and Boston lettuce, photosynthetic rates of mature leaves significantly decreased under reduced potassium treatments, with a steady or gradually increased intercellular CO2 concentration; this indicated that non-stomatal factors suppressed photosynthesis. In romaine lettuce, the photosynthetic rate was less influenced by reduced potassium levels in the nutrient solution, and the significant increase observed in leaf mass per area might contribute to maintaining photosynthesis in the leaf. The decrease in photosynthesis in mature leaves exhibited a similar trend to the decreased potassium content in the leaves within the three lettuce types, but the factor related to the reduction of photosynthesis was different.

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  • Hsiang-Yi Huang, Ching-Hsiang Hsieh
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 238-243
    Released: April 25, 2017
    [Advance publication] Released: September 27, 2016
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    The objective of this study was to determine the genetic model of fruit color in the bitter gourd (Momordica charantia L.). Six generations (P1, P2, F1, F2, BCP1, and BCP2) in the hybrid set “MS 41 × MS 47” were used to estimate the genetic effects via generation mean analysis (GMA). The fruit color of the F1 population was green implying the green color was dominant over the white color. The fruit color of the F2 population showed a continuous distribution from white to dark green indicating this trait was controlled by quantitative genes. Genetic analyses using the Royal Horticultural Society scoring system (RHS score) fitted the three parameters model (χ23 = 1.59, P = 0.6607) and showed significant to highly significant additive and dominance effects, respectively. The GMA results of the six parameters model revealed a significant additive effect on chlorophyll b concentration. Chlorophyll a and total chlorophyll concentrations were nonsignificant in all parameters. The magnitudes of additive and additive × additive gene effects were larger than those of the dominance and dominance × dominance gene effects, which revealed that additive genes were more important in the contribution to chlorophyll concentrations. Broad-sense heritability estimates for color traits were 0.39, 0.611, 0.470, and 0.460 for concentrations of chlorophyll a, chlorophyll b, total chlorophyll, and RHS score, respectively. In contrast to previous findings, with the GMA analysis we believe that the genetic model of fruit color in bitter gourd is clearly a quantitative model.

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  • Takayuki Mizuno, Naoko Fukuta, Hiroko Shimizu-Yumoto
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 244-251
    Released: April 25, 2017
    [Advance publication] Released: August 03, 2016
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    Double-flowered Eustoma, a popular cut flower, sometimes shows nonuniform coloration of its petals when harvested at the flower bud stage. At the tips of the petals, pale greenish areas remain after the flowers open. This considerably reduces the value of cut Eustoma. In this study, to identify appropriate postharvest treatments leading to normal coloration of these cut flower buds, we investigated the influence of harvest stage, temperature, sugar, and methyl jasmonate (MeJA) on petal coloration using the Eustoma ‘Voyage (Type II) Blue’. Investigation of the harvest stage, which was compared at three flower bud stages (STG2, 3, and 4), revealed that detached pale greenish flower buds (STG2 and 3) had a high probability of becoming nonuniformly colored flowers, so these stages were used for subsequent investigations. Temperature, which was investigated at 20, 25, 30, and 35°C, did not show any influence on petal coloring. Investigation of sugar treatments, such as 1% or 3% glucose or sucrose, also showed no influence. However, MeJA treatment led to a significant difference in petal coloration. The nonuniform coloration of petals was reduced by continuous exposure to MeJA vapor. Furthermore, we performed shorter MeJA treatments, such as for 1 or 2 days after harvesting, which reduced the nonuniform coloration as well as continuous MeJA exposure. To evaluate the effect of MeJA treatment on petal coloration, we measured the rate of pale green areas of petals using digital images. The analysis revealed that the greenish areas in petals exposed to MeJA vapor were significantly smaller than in petals not exposed to MeJA. In addition, there were fewer days to flowering after MeJA treatment. We concluded that postharvest treatment with MeJA is effective for reducing nonuniform coloration of early harvested flower buds of the double-flowered Eustoma ‘Voyage (Type II) Blue’.

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  • Wanita Kaewphalug, Pattana Srifah Huehne, Ajaraporn Sriboonlert
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 252-262
    Released: April 25, 2017
    [Advance publication] Released: August 25, 2016
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    Orchids are economically valuable as cut flowers and in pot plant markets. However, a juvenility phase that is too long is the main disadvantage for commercial orchids. To understand the gene involving floral transition controls in orchids, a CONSTANS-like (COL) gene in the photoperiodic flowering pathway was isolated from Dendrobium crumenatum (pigeon orchid). The cDNA isolated has an open reading frame (ORF) of 969 bp, encoding 322 amino acids. Sequence alignment based on amino acid sequences revealed that the Dendrobium crumenatum COL (DcCOL) shared a high identity with COL isolated from other plant species including Phalaenopsis COL (85%), Oryza sativa Hd1 (70%), Erycina pusilla COL5 (EpCOL5) (66%), and Arabidopsis thaliana CO (39%). DcCOL has three conserved domains (CCT, B-box I, and B-box II domains) and is classified in group I CO/COL by phylogenetic analysis in the Arabidopsis B-box zinc finger protein family. Quantitative real-time RT-PCR demonstrated DcCOL was expressed in all stages of development and all tissue types with the highest expression in floral buds and opened flowers of mature orchids. The expression pattern under photoperiod pathway demonstrated a diurnal expression. The DcCOL was accumulated in the dark in all photoperiodic conditions, i.e., long, neutral, and short days suggesting that the regulation of DcCOL was controlled in a circadian rhythm-dependent manner. The results suggested that photoperiodism is not the main factor in D. crumenatum floral induction control. This DcCOL expression pattern coincided with the D. crumenatum flowering behavior in which the flowering occurs before dawn and lasts for only 24 h implying the function of DcCOL is related to flowering.

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  • Yoshikuni Kitamura, Tatsuya Uemachi, Yukari Kato
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 263-268
    Released: April 25, 2017
    [Advance publication] Released: September 15, 2016
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    We compared transpirations and vase lives of cut hydrangea (Hydrangea spp.) flowers using two cultivars with lacecap inflorescence (‘Blue sky’ and ‘S-1’) and their mutants with hortensia inflorescence (‘BM-1’ and ‘SM-1’). There was no significant difference in the transpirations from cut flowers with the lacecap and hortensia inflorescences in the two cultivars. However, transpiration from ‘S-1’ cut flowers tended to exhibit higher transpiration than ‘SM-1’. There was also no significant difference in the vase lives of ‘Blue sky’ and ‘BM-1’. However, ‘S-1’ had a significantly shorter vase life (3 days) than its mutant ‘SM-1’. This was due to the greater number of total florets in ‘S-1’ cut flowers than ‘SM-1’. The non-decorative floret clusters and clusters of petals, stamens, and pistil of decorative florets exhibited lower temperatures than decorative sepals in both ‘Blue sky’ and ‘BM-1’ on thermal images. Therefore, we estimated the transpiration from the non-decorative florets and studied the effect of removal of non-decorative florets on the vase life of cut flowers using two lacecap cultivars, ‘Blue sky’ and ‘Fairy eye’. Estimated transpirations from the non-decorative florets of ‘Blue sky’ and ‘Fairy eye’ accounted for approximately 61.8% and 39.7%, respectively, of total transpirations per cut flower, and the removal of non-decorative florets significantly extended the vase lives of cut flowers (18 and 22 days, respectively). The difference in the contribution of the non-decorative florets to the transpiration between the cultivars is due to the difference in the number of non-decorative florets in the inflorescences. We conclude that the use of cut flowers that do not bear too many non-decorative florets and/or treatments that suppress the transpiration from non-decorative florets would be effective in extending the vase life of cut hydrangea flowers with lacecap inflorescence.

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  • Kyeong-Seong Cheon, Akira Nakatsuka, Keisuke Tasaki, Nobuo Kobayashi
    Type: Original Articles
    Volume 86 (2017) Issue 2 Pages 269-276
    Released: April 25, 2017
    [Advance publication] Released: September 17, 2016
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    Double flower form is an important trait of ornamental flower plants such as Japanese azalea because of its high visual appeal. We investigated floral phenotypes and a MADS-box C class gene to characterize floral morphology and this gene in single- and double-flowered cultivars of Japanese azaleas. Normal floral organs (sepals, petals, stamens, and carpels) were observed from each whorl of single flowers, whereas in double flowers, petaloid stamens or petals were observed from the third and fourth whorls, and there were no normal stamens or carpels in any flowers. Molecular analysis revealed that expression of the azalea AGAMOUS/PLENA (AG/PLE) homolog was lower in the inner two whorls of double flowers than in inner two whorls of single flowers, and expression of the AG/PLE homolog was higher in the double-flowered cultivars ‘Surugaman-yo’ and ‘Yodogawa’ than in other double-flowered cultivars. Moreover, sequence analysis of AG/PLE mRNA revealed deletion mutations in the coding regions of the AG/PLE homolog in ‘Surugaman-yo’ and ‘Yodogawa’. These results suggest that the double flowers of Japanese azalea cultivars are formed as the down-regulated expression and deleted sequence mutation of the azalea AG/PLE homolog.

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