‘Shiikuu’ (Citrus sp.) is cultivated on Kikai Island located in the Amami Islands, Japan, and the skin of its fruits has an aroma that is almost the same as that of ‘Bergamot’ (C. bergamia Risso et Piet.). A similar type of local citrus grows only in the northern part of the Amami Islands. In this study, the aroma of ‘Shiikuu’ was compared with that of ‘Bergamot’ and ‘Tanaka Bergamot’ (C. balotina Poit. et Turp.). Three major components were common in the three citrus accessions: “linalyl acetate”, “linalool”, and “d-limonene”, and they comprised 77–91% of the total in each aromatic constitution. The concentration of the phototoxic compounds, furocoumarins, was much lower in ‘Shiikuu’ than in ‘Bergamot’, despite the similarity of their aromas. Water distillation was suggested to be a suitable method for ‘Shiikuu’ essential oil extraction because of its small fruit with a thin flavedo. The results of a sequence-related amplified polymorphism (SRAP) analysis confirmed that ‘Shiikuu’ differs from ‘Bergamot’. ‘Shiikuu’ probably arose as a local Citrus accession derived from an incidentally dispersed seedling growing in the northern part of the Amami Islands.
We investigated the characteristics and polyploidy of pollen and fruit tissue in 2x-4x-4x ploidy chimeras induced by colchicine treatment of citrus. The pollen size of 2x-4x-4x ploidy chimeras and tetraploids was larger than that of diploids in all cultivars and strains that we investigated. The peel of the tetraploid fruit was thicker than that of diploids in all cultivars and strains, but a constant tendency was not seen in 2x-4x-4x ploidy chimera fruits. The flavedo, segment membranes, and juice sac showed diploidy and tetraploidy, the albedo showed tetraploidy only, and the pollen showed diploidy and tetraploidy in all 2x-4x-4x ploidy chimeras cultivars and strains. All plants raised from a seed, which we crossbred with diploid pollens in these individuals, showed triploidy. These results indicate that the 2x-4x-4x ploidy chimeras would be useful parents for triploid breeding by crossing with diploids like tetraploids.
Six offspring in each of 26 families and their parents in Japanese pear were evaluated regarding the fruit weight. Analysis of variance of the offspring, which estimated the between- and within-family variance, and multiple-regression of the mean value in a full-sib family with the mid-parental value (MP) and inbreeding coefficient (F) revealed that the genetic differences among families could be explained mostly by MP and F. Genotypic values of offspring in a family were assumed to be normally distributed around the multiple-regression line with the sum of within-family genetic variance and variance due to the deviation of the family-mean from the multiple-regression line. Based on the parental mean performance of 10 fruits on a single tree for five years, the coefficients of multiple-regression of mean values in a full-sib family on MP and F were 0.6263 ± 0.13 and –0.7343 ± 0.20, respectively, and the proportion of offspring with genotypic values and a fruit weight > 350 g was estimated as 23.6 and 1.3% for 0.104 and 0.3438 F values, respectively, in individuals from a cross with MP = 300 g.
Intergeneric hybrid plants were obtained by crosses between spinach mustard (Brassica rapa L. Perviridis Group) and arugula (Eruca sativa Mill.), both belonging to the Brassicaceae family, followed by ovule culture. The morphological characteristics of the hybrid were as follows: inflorescences and leaf blades were intermediate between the parents, while the sequence of the placenta was B. rapa L. type, and the shape of the stalk leaf base was E. sativa Mill. type. GISH analysis by probing with total genomic DNA of either B. rapa L. or E. sativa Mill. confirmed the hybridity of the amphihaploid. Analysis of the secondary metabolites revealed that the crossing hybrid contained all the glucosinolates and isothiocyanates that were found in both species, in addition to the erucin precursor (4-methylthiobutyl-GSL: Glucoerucin) and sulforaphane precursor (4-methylsulfinylbutyl-GSL: Glucoraphanin), both specific to arugula. These results demonstrate that intergeneric crosses between B. rapa L. and E. sativa Mill. are expected to expand genetic variation and lead to the successful breeding of new value-added tender greens that meet consumer needs.
In this experiment, we investigated the physical and chemical properties of foamed waste glass, and its application for the growth of Japanese mustard spinach (Brassica rapa L. Perviridis Group), in order to assess the utility of foamed waste glass as a culture medium for horticulture. Foamed waste glass with a particle size of less than 4 mm led to more favorable water availability than larger particle sizes. When mixing particles of less than 4 and 4–15 mm, the availability water was adjusted. The pH and exchangeable magnesium levels of foamed waste glass were higher than those of the commonly used culture medium of Masa (decomposed granite) and bark compost. On the other hand, CEC of foamed waste glass was lower than that of the common culture medium. The pH and exchangeable magnesium levels were both decreased by draining water, although the decrease of the pH was insufficient for cultivation. Foamed waste glass with an adjusted pH of 6 using dilute sulfuric acid led to the more favorable growth of Japanese mustard spinach than alkaline conditions. We conclude that foamed waste glass with a pH adjusted to 6 and with a particle size of less than 4 mm at rates of 25 to 75% is effective as a culture medium for horticulture.
The incidence of blossom-end rot in relation to the Ca concentration in tomato fruits as affected by a long daily photoperiod was examined using supplemental lighting (60~168 μmol・m–2・s–1 of PPFD at plant canopies) in autumn cropping. Low Ca solutions (1/4Ca or 1/8Ca of Enshi standard solution) were supplied for the medium-sized fruit tomato cultivar ‘Cindy Sweet’. Supplemental lighting significantly decreased both total and water-soluble Ca concentrations in distal fruit tissue and aggravated the incidence of BER in the tomato. No significant difference was observed in the fruit growth rate; however, a positive relationship was found between leaf stomatal conductance and the intensity of supplemental lighting. Therefore active leaf transpiration after sunset caused by supplemental lighting may have resulted in decreased Ca translocation into the fruit through xylem vessels. In addition to the vigorous growth and increased Ca demand of fruit resulting from a high temperature and strong solar radiation, reduced Ca translocation into the fruit due to a short dark period may aggravate tomato fruit susceptibility to BER in the late spring to mid-summer season.
In Japan, grape berries are generally eaten only after the skin has been peeled off. The Japanese grape cultivar ‘Shine Muscat’ is consumed as a whole fruit that is not peeled prior to consumption. However, the palatability of unpeeled fruit varies with cultivating conditions such as seedless treatments and irrigation. Because of the improved edibility of whole berries, we investigated the effect of an application of 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) with 25 ppm gibberellic acid solution at the full bloom stage on the texture of whole fruit. The palatability of unpeeled fruit was evaluated based on the physical properties, skin thickness, and sensory evaluation. Treatments using the following four CPPU concentrations were tested: 10, 5, 2 ppm and no-application. The results of the physical property test revealed that, compared with the 2 ppm and no-application CPPU treatments, the 10 and 5 ppm CPPU treatments resulted in easily deformed berries with a non-friable skin. In particular, the 10 ppm CPPU treatment led to the skin with low friability during mastication. Although the thickness of the skin, peeled by hand, was not different between the 2 ppm and no application CPPU treatments, there was a tendency toward an increase in the thickness with a rise in CPPU concentrations. The 10 ppm CPPU treatment led to the lowest scores on sensory evaluation and the physical property test. As the results of sensory evaluation, the 5 ppm CPPU treatment scored lower than the 2 ppm CPPU treatment in terms of the texture of berries. Therefore, it was suggested that a 10 and 5 ppm CPPU application reduces the palatability of fruit with skin. The results obtained in this study demonstrate that 10 and 5 ppm CPPU treatments at full bloom have a negative effect on the palatability of whole fruit.
Impatiens (Impatiens walleriana Hook. f.), whose cultivation requires heating in a greenhouse during the winter season, was used in this experiment to investigate the effects of root-zone heating on growth, flowering, and energy consumption. Four combinations of minimum air temperatures and root-zone temperatures: 8°C/non-heating, 13°C/non-heating, 8°C/13°C, and 8°C/18°C, were set, respectively, and the Impatiens plants were cultivated from February 1 to April 22, 2014 in a greenhouse. The number of leaves, leaf area, and dry weight of the top increased with rising average root-zone temperatures, and there was a close relationship between growth and the average root-zone temperature. The flowering season was about 10 days earlier at 8°C/13°C and 8°C/18°C than that at 13°C/non-heating. Energy consumption at 8°C/18°C, when growth and flowering were the most accelerated, was reduced by about 32% compared with that at 13°C/non-heating.
Beet (Beta vulgaris L.), belonging to the family Amaranthaceae, contains a large amount of betalain, a markedly antioxidant pigment. However, few studies have been conducted to examine the betalain content in different varieties in Japan. Beet is usually harvested when the diameter of the taproot (edible root) has reached approximately five to six centimeters. However, few standards for its shipment to market have been established, and only limited information on the appropriate period to harvest beet crops containing the highest betalain content is available. The present study, involving four varieties of beet: ‘Detroit Dark Red’, ‘Saffron Yellow’, ‘Gorgo’, and ‘Rivolta’, with taproots of different colors, was conducted to examine differences in the betalain content among the varieties, and changes in the betalain content in red beet (‘Detroit Dark Red’) at six different growth stages. ‘Detroit Dark Red’, a type of red beet, contained the highest betalain content. The betalain content on a fresh weight basis in ‘Detroit Dark Red’ was the highest when the diameter of the taproots had reached approximately five to six centimeters, indicating that betalain intake from ‘Detroit Dark Red’ harvested around this period would be optimal.
To establish an effective night-break (NB) lighting system for the commercial production of chrysanthemum, it is necessary to clarify the optimum timing and duration of lighting at night. Therefore, we determined the duration of darkness before the achievement of maximum sensitivity to NB (dusk-NBmax) and the relationship between the timing and duration of light exposure that optimized the inhibition of flowering in the chrysanthemum cultivars ‘Jimba’ and ‘Iwano-hakusen’. The duration of dusk-NBmax was 10 h and 15–25 min and 7.5–8 h for ‘Jimba’ and ‘Iwano-hakusen’, respectively. In both cultivars, the most effective NB timing was achieved by extending the illumination by 0.5–1 h after the end of NBmax. The inhibitory effects of NB on flowering increased in proportion to the length of NB; however, further extension of NB adversely reduced its effects. The reduction in the NB effect induced by extending the duration of illumination was associated with the presence or absence of darkness before NB. On the basis of these results, we propose a practical lighting system for the optimum inhibition of flowering in chrysanthemum, whereby the most effective timing and duration of NB are 4 h after dusk and 0.5–1 h after dusk-Nbmax, respectively, for each cultivar.
The effects of abscisic acid (ABA)-containing fertilizer treatment at a late growing stage (from 25 to 40 days after véraison) on the color development and quality of tetraploid red grape cultivars ‘Aki Queen’ and ‘Ruby Roman’, undergoing seedless cultivation, were investigated. The treatments at the late growing stage promoted ideal coloration without negative effects such as over-coloration or a decrease in the sugar content, which indicated the beneficial effect of color improvement induced by this fertilizer treated at the late growing stage. The enhanced accumulation of total anthocyanins due to this treatment was more notable in ‘Aki Queen’ than in ‘Ruby Roman’. Time-dependent anthocyanin accumulation and the expression of genes involved in anthocyanin biosynthesis and related transcription factors, VlMybA1-2 and VlMybA1-3, and expression of the enzyme UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) revealed the difference between these cultivars: all values were higher in ‘Ruby Roman’ than in ‘Aki Queen’ at the late stage of berry development, suggesting that higher levels of anthocyanins are accumulated in ‘Ruby Roman’.
The effect of shading in suspended storage under the eaves on the quality of seed bulbs of Allium × wakegi Araki cv. Kan Shirazu was investigated for improving the seed bulb quality, i.e., increase of transplantable bulbs, increases of the bulb weight and sprouting after the dormant period, and decrease of softened bulbs, for spring-harvesting cultivation. Bulbs in suspended storage under the eaves were dormant until mid-August. An increase in the respiration rate and rapid bulb softening were observed in early September in the control, but shading during storage suppressed the increase in the respiration rate. Shading also prevented the decrease in the total sugar content of the dry bulbs in September. The bulb weight and rate of softened bulbs under shading were 10 and 20% lower than those of the control, respectively, and shading increased the rate of transplantable bulbs by 20% at the end of the year, being the end of the transplant season.
We studied methods for pollination, disbudding, and the dilution of pollen for artificial pollination to reduce pollen consumption in ‘Rainbow Red’ kiwifruit (Actinidia chinensis). Pollination using a rechargeable pollen dust sprayer could reduce the volume of dry pollen mixture and work time. In disbudding, if the number of flowers was two or three per bearing shoot, the quantity of dry pollen mixture sprayed could be reduced without decreasing the yield. On spraying a diluted dry pollen mixture, the seed number was reduced and the incidence of malformed fruit increased with the dilution below 5%. Therefore, we concluded that the appropriate dry pollen mixture dilution was above 6.7%. The volume of pollen consumption for artificial pollination should be reduced using rechargeable pollen dust sprayers, two or three pollinating flowers per bearing shoot, and the spraying of a dry pollen mixture dilution above 6.7%. Pollen consumption with artificial pollination could be reduced using a combination of these methods.
The elimination of Hop stunt viroid (HSVd), Citrus dwarfing viroid (CDVd), and Citrus viroid VI (CVd-VI) from Satsuma mandarin (Citrus unshu Marc.) by shoot-tip grafting was attempted. Standard shoot-tip grafting was performed after 0.2-mm-long shoot tips were excised from young shoots of the Satsuma mandarin cultivar ‘Miekinansangou’ that was infected with HSVd, CDV, and CVd-VI. To clarify the effect of temperature on viroid elimination, some trees were pre-heated alternately for 4 h at 40°C and 4 h at 25°C, whereas others were kept at a constant temperature of 28°C. After successful shoot-tip grafting and subsequent side-grafting to seedlings of flat lemon (Citrus depressa Hayata), plantlets were tested by RT-PCR for the absence of viroids. The RT-PCR indicated that CDVd was the most easily eliminated viroid, followed by CVd-VI and HSVd, with or without heat treatment. The elimination rate of each viroid was slightly higher among plantlets with heat treatment than those without such treatment, but without significance. This is the first report on eliminating CDVd and CVd-VI from Satsuma mandarin. The results suggest that shoot-tip grafting with 0.2-mm-long shoot tips is a practical method for eliminating multiple viroids from Satsuma mandarin.
In order to develop new raspberry varieties adaptable to Japan with high quality and functionality, we aimed to produce interspecific hybrids between Rubus parvifolius L., a wild species native to Japan, and the ‘Indian Summer’ raspberry (R. idaeus L.). The morphological characteristics, such as the leaf, flower, and fruit, and random amplified polymorphic DNA (RAPD) analysis revealed that ‘07RUBIXP01’ was an interspecific hybrid. Although ‘07RUBIXP01’ had small thorns, it showed vigorous growth in the warm environment and had a significantly larger fruit compared with the parents. Also, ‘07RUBIXP01’ showed values intermediate between those of the parents for total polyphenol, anthocyanin, and ellagitannin contents. In particular, it showed an ellagitannin content that was about four times higher than that of ‘Indian Summer’. In sugar and organic acid analyses, a higher sugar acid ratio was noted compared with the parents. ‘07RUBIXP01’ was registered as a new variety in 2012 (variety registration no. 21801), and it would be a useful raspberry for growing in warm regions of Japan.