We carried out colchicine treatment of lateral buds and their grafting in some monoembryonic citrus cultivars to induce tetraploid plants. Among the grafted plants, 19 eutetraploid plants were obtained from 8 cultivars. The successful cultivars were ‘Ootachibana’, ‘Suisho-buntan’, ‘Nouma-benihassaku’, ‘Kiyomi’, ‘Aki-tangor’ ‘Nishinokaori’, ‘Ariake’ and ‘Hiroshimakaken No. 11’. Then efficiency of triploid production was very high (7.68 triploid/fruit) when the tetraploid ‘Kiyomi’ were used as a seed parent. The efficiency was higher than those for crossing trials of diploid ‘Kiyomi’ × diploid ‘Ootachibana’ (0.05 triploid/a fruit) and diploid ‘Kiyomi’ × the tetraploid ‘Ootachibana’ (0.16 triploids/a fruit). In addition, when some other monoembryonic tetraploids were crossed with diploid cultivars, they also bore triploid plants efficiently as seed parents, such as 0.47–0.91 in the tetraploid ‘Ariake’, 2.13–2.86 in the tetraploid ‘Hyuganatsu’, 4.25–6.00 in tetraploid ‘Clementine’, 6.79–11.33 in tetraploid ‘Kiyomi’. Although the sizes of the hybrid seeds were smaller than the averaged diploid seeds, but the seeds matured fully and germinated well (79.1%) in vitro. This study showed that 99.8% of the raised hybrid plants were triploid (487 plants).

View full abstract

Crossings between triploid and diploid in cultivated Japanese butterbur (Petasites japonicus Fr. Schmidt) were made and the agronomic traits of hybrid plants for harvesting petioles were investigated. As a result hybrid plants from the crosses of ‘Aichiwasebuki’ (triploid) × ‘Mizubuki’ (diploid, native cultivar of Gunma pref.), ‘Mizubuki’ (triploid, native cultivar of Tokushima pref.) × ‘Mizubuki’ (Gunma) and ‘Kibiji’ (triploid) × ‘Mizubuki’ (Gunma) were obtained. Some hybrid plants from ‘Aichiwasebuki’ × ‘Mizubuki’ (Gunma) grew more vigorously than their parents. Among hybrid plants, there were several hybrids that did not develop anthocyanin pigments at petioles. By flow cytometry, the hybrid plant ‘AM-35’ was estimated as diploid, and ‘AM-1’ and ‘AM-51’ as aneuploid. ‘AM-1’ showed early maturing, high petiole yield, and less anthocyanin pigments at the petioles compared with ‘Aichiwasebuki’. Therefore, there is a possibility of selecting a new cultivar for harvesting petioles from hybrid plants of ‘Aichiwasebuki’ (triploid) and ‘Mizubuki’ (diploid, Gunma).

View full abstract

Nodal culture of flower stalk was carried out to maintain the breeding line of lettuce. The flower buds of lettuce and its interspecific hybrids with Lactuca serriola and tetraploid lettuce were initiated on 40th to 34th node of main stem and bloomed at 140 to 110 days after sowing. The explants from node of secondary stem of tetraploid lettuce and L. serriola × lettuce proliferated leaf buds in a rate of 44.8 and 19.9%, respectively, indicating that the explants from the developed stage of flower seemed to form flower bud rather than leaf bud or shoot. Then, the explants of secondary stem from the lower node of the main stem showed higher shoot formation than those from the upper node. When the terminal flower of the main stem bloomed, the percentage of explants which formed leaf buds (5.6%) was less than that of none-bloomed explants (55.1%). Explants from lower node of secondary stalk formed leaf bud more frequently than those of upper node. This study enables the maintenance of the plants on breeding lines of lettuce even after the seed production by node culture of flower stalk.

View full abstract

We investigated the effects of bottom-heat (BH) treatment during low-air-temperature (5–10°C) storage on the rooting of eggplant grafted-cuttings that were planted after storage. BH treatment was applied by holding the cut end of cuttings in warmed water. Root growth of cuttings following storage tended to be much improved by BH treatment temperatures ranging from 26 to 31°C. BH treatment should end just before rooting begins in order to avoid the inhibition of root growth caused by root damage during planting. In this study, optimal BH treatment duration is thought to be 3 days, because rooting during storage was observed 4 days after starting treatment when BH treatment was performed up to 5 days. BH treatment was applied to the grafted-cuttings for 3 days using a BH treatment temperature of 27°C at the beginning of 14 days’ storage. The cuttings stored with BH treatment were planted in the growing medium, and then grown for 14 days. Root fresh weight of the grafted plant obtained from cuttings that received BH treatment was 1.4 and 2.8 times greater than those that were stored without the treatment or not stored at all, respectively.

View full abstract

The most suitable period to reintroduce protocorms of Habenaria radiata that had been gel covered and inoculated with orchid mycorrhizal fungi to a habitat in order to restore the population was investigated. Seed germination rates changed during the sowing season. In October, the germination rate was high except in the dark, but there were no differences in the seed germination rate among different light conditions and dark condition in May the following year. The germination of H. radiata seeds in a habitat started during late March and peaked in late April, then fungal infection of protocorms began. Most of the protocorms were infected with fungi in late May. Protocorms inoculated with orchid mycorrhizal fungi and covered with gel were reintroduced to the habitat between late May and early July. The protocorms reintroduced during late May or mid June showed the best growth.

View full abstract

In order to prevent on-tree fruit softening in Japanese persimmon ‘Saijo’ (Diospyros kaki Thunb.), the effects of foliar application of MnSO₄ and soil application of manganese manure along with soil pH adjustment to acidity were investigated. Foliar application of MnSO₄ did not affect Mn concentration in the leaves, calyx and flesh. However, soil application of manganese after pH adjustment by sulfur powder application remarkably increased in the Mn concentration in the leaves, calyx, flesh and one-year-old shoots. In accordance with this increase, ethylene production in the fruit was decreased and the occurrence of fruit softening reduced. These results suggested that the maintenance of Mn concentration over 100 ppm by Mn manure application to the soil and pH reduction is necessary to prevent on-tree fruit softening of Japanese persimmon.

View full abstract

The absorption and translocation of urea applied to the foliage of satsuma mandarin at the sprouting stage was monitored for two years using the ¹⁵N-tracer method in potted and field-planted trees. Urea applied to foliage even in late March was absorbed into old leaves, regardless of combination with or without petroleum oil emulsion. Of the urea absorbed, 57% moved to newly developed organs until mid-June and almost none moved to the roots. The absorbance of urea applied to the foliage increased with the number of applications up to at least three-fold and about forty percent of the applied the amount was absorbed. These finding’s suggest that urea applied in late March or early April effectively increases nitrogen level of trees with nitrogen deficiency.

View full abstract

The effect of mother-stem length on cut flower stem yield and characteristic form during the high-rack training system for rose plants ‘Asami·Red’ (syn. ‘Rote Rose’) was studied for five different mother-stem lengths, 0 cm (control; arching), 5 cm, 10 cm, 15 cm and 20 cm for a year. Three months after being planted on a high rockwool bench in September 1997, all scion stems and Rosa odorata Sweet rootstock stems were bent below the horizontal position. The yield of cut flowers was much higher in the 15 cm and 20 cm treatments than in the 0 cm, 5 cm and 10 cm treatments. The characteristic form of the cut flowers, i.e., stem length, stem weight and weight/length ratio (g·cm⁻¹), after 0 cm treatment was superior to those after treatments. However, the characteristics of cut flowers in the high-rack system was commercially acceptable and almost the same for each of the other four mother-stem lengths. These results suggest that mother-stem lengths of 15 to 20 cm may be the most favourable for the high-rack training system of ‘Asami·Red’ rose plants.

View full abstract

Effect of gibberellin application on vegetative propagation and flowering was studied in Saxifraga stolonifera Meerb. Vegetative propagation was promoted by gibberellin spraying under open-field conditions. The number of runners increased by gibberellin sprays and lateral buds were grown by 50–200 mg·L⁻¹ gibberellin in pot culture under room conditions. The leaf color after spraying with a high concentration of gibberellin was lighter than that with low concentrations or water. Flower stalk development and flowering were promoted by application of 50–200 mg·L⁻¹ gibberellin sprays. The length of spikes was increased using 10–50 mg·L⁻¹ gibberellin. In addition, when cuttings from the top of the runners were used after 50 mg·L⁻¹ gibberellin treatment to the mother plants, differentiation of young plants was promoted by 50 mg·L⁻¹ gibberellin in comparison with that after spraying water. The growth of young plants induced with gibberellins was, however, slower compared with that of controls. Results indicate that vegetative propagation and flowering are promoted in Saxifraga stolonifera M. by application of 50 mg·L⁻¹ gibberellin.

View full abstract

The effects of taping, branch age, position, and the extent of phloem removal of the girdle on healing of the girdle and fruit characteristics in grapes were investigated. Retaining a part of the phloem tissue, which was the thin innermost-layer tissue of phloem, did not increase anthocyanin concentration of skins or diminish the increase in total soluble solids (TSS) of berries. In contrast, complete removal of phloem tissue increased the anthocyanin concentration and TSS, whether the girdle was taped or exposed. When the girdle was exposed, necrosis appeared in part of the pith. Callus developed faster in old branches than in young branches. However, when the girdles were covered with vinyl-tape, branch age did not affect the rate of callus development. Furthermore, girdled areas healed directly and rapidly eventhough phloem tissue was completely removed. Trunk girdling height of 0.4, 0.7, 1.0, 1.3 m above the ground did not affect the fruit characteristics. When the girdle was taped, girdled areas healed rapidly and widely after this treatment, but anthocyanin concentration and TSS increased. Based on these results, complete removal of phloem tissue and covering of the girdled areas with tape is necessary to increase anthocyanin concentration and TSS without causing necrosis in pith.

View full abstract

A study was carried out to develop a forcing culture of Japanese butterbur using one-year-old rootstocks ‘Haruibuki’ and ‘Mizubuki’ (the latter a native cultivar of Gunma pref.) with the objective of harvesting spikes between January and February and petioles in March. In the initial phase of this experiment, rootstocks with spikes were dug out in December, and kept in cold storage, then rootstocks with spikes were planted in a hotbed after removing them from the refrigerator in January, February and March. When rootstocks were immediately taken from the refrigerator, the color of bracts was too light for the spikes to be marketed. The color of bracts became deep green and the quality was improved by exposure to sunlight for six days after planting rootstocks in a greenhouse hotbed. When rootstocks were planted in March, spikes were loose since bracts were opened. When rootstocks were planted in a hotbed in January, it was possible to harvest S-size petioles (length: 40~50 cm) in March after harvesting spikes in January. It was thought that ‘Haruibuki’ was more suitable than ‘Mizubuki’ for forcing culture using one-year-old rootstocks, judging from the total spike and petiole yield.

View full abstract

Early shipping of immature fruit of the Japanese pepper (Zanthoxylum piperitum (L.) DC.) grown under greenhouse conditions is advantageous for commanding a higher price for the fruit. However, in order to achieve a yield per unit area of fruit under greenhouse conditions, artificial pollination is required. For successful pollination, pollen with a high potential for germination must be used. Additionally identification of optimal conditions for pollen germination is also required. In this paper, we identified the optimal concentrations of sucrose, agar, and boric acid, as well as the optimal temperature for pollen germination and pollen tube length for fresh pollen of Japanese pepper at the beginning of flowering and the full bloom stage under an artificial environments. With 2% agar media, the highest percentage of germination at the beginning of flowering and at the full bloom stages were obtained at 15% and 15–20% respectively. Pollen tube length at both times excelled comparatively at 15–25% sucrose. The highest germination at both times was obtained at 30°C. Pollen tube length at the beginning of flowering and full bloom stage were comparatively higher at 20–30°C and 15–35°C, respectively. Adding 100–1000 ppm boric acid enhanced pollen germination percentage and tube length.

View full abstract

This experiment was intended to examine the effects of nitrogen absorbed during summer and autumn on shoot growth, fruit quality and yield of forced cultured ‘Muscat of Alexandria’ grape. After harvest in May, three groups of trees (each group consisted of three trees) were applied for fertilizer experiment. Nitrogen was fertilized for each group by three different levels of 5 g, 10 g and 15 g N·m⁻² in summer and the same amount of nitrogen (12 g N·m⁻²) was applied for all groups in autumn. Warming started on December 14. Before blooming, there were no differences in shoot elongation between plants treated with 10 g and 15 g. However, significantly less growth was observed in those treated with 5 g. After blooming, the difference in shoot elongation became less than that before blooming and there was almost no difference in cluster weight or berry size and yield among treatments. However, pH and Brix in juice were obviously less in plants treated with 5 g. Correlation analysis of the leaf area, flower cluster numbers per shoot, fruit quality and yield was performed with respect to nitrogen absorbed in summer and autumn. Consequently, the appropriate amount of nitrogen absorbed in summer or autumn is supposed to be 8 g·m⁻² per plant.

View full abstract

We designed a new device for grapevine flower thinning to improve task efficiency and lighten the work burden. The prototype is a palm-sized tool equipped with two semicircular blades. Each blade is surrounded by a support plate, and the two support plates are connected to each other by a curved spring. The tool is used by placing the axis of the primary rachis within the circular space between the blades and locking the support plates together with the provided locking clip. Then, the cutting tool is slid downward along the primary rachis to cut off the unwanted flowers. In a pilot experiment conducted to test the prototype tool, the time required for flower thinning of the seedless cultivars ‘Aki Queen’ and ‘Kyoho’ (Vitis vinifera × V. labruscana) was shortened by 24%–39% when the prototype was used, compared to the time required using horticultural scissors. Similarly, this tool reduced the time required for flower thinning of the seeded cultivar `Kyoho' by about 35%. The tool did not cause large scars on the surface of the primary axis after its use, and did not have any undesirable effect on fruit quality. Therefore, this new cutter is a useful labor-saving tool for flower thinning of both seedless and seeded cultured grapevine varieties in accordance with established practice.

View full abstract

The objective of this study was to establish the cultivation technique for high yield with high profit in mother fern green asparagus (Asparagus officinalis L.) cultivation. Effects of pinching and lower branch pruning on the yield and size of spears were investigated. The marketable yield, especially large (L) class spear yield with high unit price was the highest in both the summer and subsequent spring seasons, when mother ferns are pinched to a 140 cm height with removal of the lower branches at a 50 cm height. The marketable yield in summer spears showed maximum values when the width between pinching and the lowest branch heights was 80~90 cm. The marketable yield of spears in the subsequent spring increased with increases in both the width of pinching and the lowest branch height to 90 cm.

View full abstract

This study investigated cultivation techniques to achieve high yield with high quality in mother fern green asparagus (Asparagus officinalis L.) cultivation. The effects of training with a net and time of pruning secondary branches on the yield and size of spears were investigated. Training with 10 cm and 20 cm mesh vertical nets increased the yield of dense green spears as compared with control, and 10 cm mesh net gave enough working space between the beds to allow the use of ambulatory control machines. The marketable yield, especially high price L class spear yield was increased by removing secondary branches of mother ferns by the end of June.

View full abstract

To improve the yield of sweet cherries (Prunus avium L.) grown by hedge-row training, the following two methods were compared: increased numbers of spurs and bouquet spurs to improve the spur composition and narrowed row intervals to increase planting density. To develop spurs and bouquet spurs, 30 cm long branches were positioned at 30 cm intervals on lateral branches in addition to the conventional spur development from 5 cm current shoots. Although this measure decreased the number of bouquet spurs, it increased the total number of spurs including the conventional short spurs to improve the yield to 1,024 kg·10 a⁻¹ from 557 kg·10 a⁻¹ using conventional hedge-row training. However, this method decreased solar radiation in the tree crowns thereby lowering fruit quality. In contrast, increasing planting density from 3-m intervals to 2- or 1.5-m intervals did not affect fruit quality. Moreover, in contrast to a yield of 588 kg·10 a⁻¹ when row intervals were 3 m, the row intervals narrowed to 2 m and 1.5 m improved the yield to 881 kg·10 a⁻¹ and 1,101 kg·10 a⁻¹, respectively. The above results show that decreasing row intervals is an effective method for increasing the yield of sweet cherries grown by hedge-row training without lowering fruit quality.

View full abstract

Effects of temperature at various stages during flower bud development on flowering time and cut flower quality were investigated in summer-to-autumn flowering-type ‘Iwa-no-hakusen’ chrysanthemum. Plants grown in a plastic green house were transferred to artificial climate rooms at 0, 5, 10, 15 and 20 days after the start of short days, and were grown under control, low or high temperature for 10 days. The artificial climate rooms were maintained at 25/20°C (day/night) for control temperature, and 20/15°C or 30/25°C in 2005 and 17/12°C or 33/28°C in 2006 for low or high temperature regimens, respectively. The stage that was most sensitive to temperature for anthesis was during petal formation and flower budding in 2005. The development of flower bud after flower budding was delayed by high temperature at this stage, and the number of days to anthesis was increased. In 2006, this stage was extended by a more severe low or high temperature regimen before petal formation compared to that in 2005. High temperature during the late stage of involucre formation and late stage of floret formation increased the weight of inflorescence and number of florets, and decreased the percentage of disk florets, resulting in preferable cut flower quality. In conclusion, unstable temperature during petal formation and flower budding contributes to the annual fluctuation in the flowering time of ‘Iwa-no-hakusen’ chrysanthemum.

View full abstract

To establish a stable production method for soft ripe ‘Saijo’ persimmon (Diospyros kaki Thunb.) fruit, the fruit were treated with fatty acids or ethylene after several weeks’ storage at 0°C. Softening of the fruit first occurred in the vicinity of the calyx. Partial softening was observed at 23, 16 and 3 days after the beginning of treatment in the control, and those treated with 100 μL linolenic acid and 100 ppm ethylene for 48 hours, respectively. With each treatment, the fruit soft-ripened (complete removal of astringency) 3 days after partial softening. All the ethylene treated fruit soft-ripened at one time 6 days after the beginning of treatment. Ethylene treatment was found to be the fastest and the most reliable method for producing soft ripe ‘Saijo’. Coloration in the ethylene-treated fruit was improved and fruit firmness decreased linearly. Soluble tannin concentration began to decrease 3 days after the beginning of treatment and astringency was removed completely on the sixth day. Fruit that was stored at 0°C for 2 to 8 weeks and then treated with ethylene soft-ripened 6 days after beginning of treatment. When fruit were stored for longer than 4 weeks at 0°C and then treated with ethylene, cracking occurred in the fruit during the course of soft-ripening.

View full abstract

Physiology of potted carnations under low light intensity was evaluated in order to improve their postharvest quality. Light compensation points of single leaves were estimated at photosynthetic photon flux density (PPFD) of 10.3 and 12.9 μmol·m⁻²·s⁻¹ for ‘My fair lady’ and ‘Scarlet’, respectively. Fv/Fm, φPSII and chlorophyll concentration in the leaves remained high under 120 μmol·m⁻²·s⁻¹ PPFD (16 h of light) but were significantly decreased under 10 μmol·m⁻²·s⁻¹. Under 10 μmol·m⁻²·s⁻¹ PPFD, concentrations of sugars and anthocyanin in petals decreased. Moreover, development of flower buds and unfolding of flowers were suppressed and thus potted plant longevity was short at a low light intensity. These findings suggested that low light intensity less than light compensation point resulted in a low photosynthesis rate, shortage of sugar accumulation, and reduced longevity of potted plants and florets. In ‘Scarlet’ maintained under 10 μmol·m⁻²·s⁻¹, treatments with 30 ppm 5-aminolevulinic acid (ALA) alleviated the decrements of chlorophyll concentrations and φPSII, and thereby slightly improved the numbers of unfolded flowers, and longevity of florets and potted plants. In ‘My fair lady’, treatments with 30 and 150 ppm ALA significantly prolonged the longevity of potted plant under 5 μmol·m⁻²·s⁻¹ (24 h of light). In ‘My fair lady’, treatments with 30 ppm ALA alleviated the decrease in chlorophyll concentration but did not affect either the photosynthesis rate or light compensation point under 15 μmol·m⁻²·s⁻¹ (12 h of light).

View full abstract

To enhance carotenoid accumulation in the flesh of Japanese persimmons by postharvest treatment, the concentration of carotenoids and the expression of carotenoid biosynthetic genes were investigated at different storage temperatures, 25°C, 10°C and room temperature (about 15.6°C). At 25°C, the concentrations increased not only in carotenes (lycopene, β-carotene and α-carotene), which were synthesized upstream to the carotenoid biosynthetic pathway, but also in xanthophylls (β-cryptoxanthin, zeaxanthin and lutein), which were synthesized downstream to the pathway, Especially in β-cryptoxanthin, the increase was remarkable. The gene expression of lycopene β-cyclase (DK-LCYb) and β-ring hydroxylase (DK-HYb), which are related to synthesis of β-cryptoxanthin and its precursor (β-carotene), was higher at 25°C than at other temperatures. These results suggested that the storage temperature at 25°C was good for carotenoid accumulation. However, at 10°C, the massive increase was observed only in the carotene concentration, especially in lycopene concentration. During 10°C storage, the decrease in gene expression of phytoene synthase (DK-PSY) and ζ-carotene desaturase (DK-ZDS), which are related to synthesis of phytoene and lycopene, was small, although, the gene expression of DK-LCYb and DK-HYb decreased strikingly. At room temperature, carotenoid concentrations and gene expressions were between those at 25°C and 10°C.

View full abstract

A survey to determine preferences among Japanese consumers for Satsuma mandarin (Citrus unshiu Marcow.) produced by different managing methods or cultural practices was carried out. Respondents included this study were aged 16 (sixteen) years and above; the sample size was 302 of which 127 were males and 175 were females. The fruit production systems under which fruits used in the study were three and they included, Production in open field under conventional management; Water stress—type I—water stress irrigation system without creasing feature; Water stress—type II—water stress irrigation system with creasing feature. Both water stress production types involved growing fruits in open fields that were covered with a water permeable sheet. Of the three systems, fruits produced under type II system had the highest preference at 64.5%, this was ascribed to the fruits having nice flavor and a favorable sugar to acid ratio. The second most preferred fruits were those produced under Water stress type I system, with a 19.9% preference. Conventionally produced fruits had the lowest preference (15.6%). Preference of Water stress type II fruits increased with respondents’ age, this trend was clearly demonstrated with respect to female respondents. There is a great difference in respondents’ reaction to sweetness among those production systems. However, with respect to sourness no differences were detected relative to all the three production systems. As for appearance, respondents mostly preferred Water stress type I fruits or conventionally produced fruits and considered Water stress type II fruits as inferior. Water stress type II fruits were considered the least easy to peel.

View full abstract

Powdery white and ball-like structures are often observed on spinach leaves and are often mistaken for foreign hazardous matters by consumers. We observed and analyzed these powders. The diameter of the powder grains was about 0.1–0.2 mm, and they were attached on projections from the surface of the leaves. The powders were not solved in water, but were destroyed by chloroform/methanol. Depressed areas were observed on the ball-like shapes when dipped in ammonium sulfate solution. The water concentration was determined to be about 90%. It is considered that the white powder is composed of a lipophilic semipermeable membrane that wraps around aqueous solution. The aqueous extract of the powders contained oxalic acid, citric acid and malic acid, and a very slight amount of amino acids and free sugars.

View full abstract

The flower colors of Yunnan camellia (Camellia reticulata Lindl., Theaceae) were measured using a device that indicates values by the Munsell color system. The device (ColorReader CR-11, Konica Minolta Sensing, Co., Japan) indicates the numbers of three dimensions (H V/C) that specify the petal color. In a wild C. reticulata tree in Chuxiong City, Yunnan Province, China, five flowers (each having 5–8 petals) showed the same color (7.5RP 4/12) with few exceptions at the outermost petals. In five old trees (ages 200–600), the flower colors were indicated as 7.5RP 4/12, 10RP 3/10 and 5RP 4/12 and showed little variation within individuals. Two horticultural cultivars, ‘Tali Camellia’ and ‘Sleeping Beauty’, cultivated in the Kunming Botanical Garden, were measured. In ‘Tali Camellia’, the mode of petal colors in both fully bloomed and senescent flowers was 7.5RP 4/12, the same as in wild C. reticulata. In ‘Sleeping Beauty’, the petal color of freshly bloomed flowers was 2.5RP 6/10, while 2.5RP 6/8 in older flowers. Both freshly blooming and older flowers of ‘Sleeping Beauty’ showed the same “hue”, however, the mean “value” of petal colors in older flowers was greater than that of freshly blooming flowers, and the mean “chroma” in older flowers was smaller than that of freshly blooming flowers. This device can be useful for outdoor measurement of flower colors for both wild and cultivated Yunnan camellia.

View full abstract