Six lines of Meiwa kumquat (Fortunella crassifolia Swingle) showing tetraploidy (No.5, No.6, No.8, No.12, No.18 and No.19), which had been induced by treating the nucellar embryos with colchicines, were investigated for ploidy level, origin and horticultural characteristics. Furthermore, these tetraploid plants were crossed with diploid kumquats for triploid production. All tetraploid plants were confirmed to be derived from the nucellar embryo of Meiwa kumquat by investigation of chromosome composition with chromomycin A3 staining. Flow cytometric analysis and chromosome observation of young leaves demonstrated that No.8 was a ploidy chimera that was both diploid and tetraploid. Five lines showing tetraploidy had the typical morphological characteristics of tetraploid Citrus plants, such as large leaves, flowers and pollen grains with low pollen fertility. However, these tetraploid plants have desirable traits for kumquat such as thicker pericarp, high sugar content and smaller number of developed seeds. No.8 had horticultural characteristics that were similar to those of tetraploid plants excluding the dermal system. When their polyploids were crossed with some diploid cultivars, triploid progenies were obtained from almost all cross combinations.

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We conducted a diallel analysis using an 8 × 8 half-diallel cross among inbred lines of the Japanese radish ‘Sakurajima daikon’ to obtain genetic information concerning its root weight and hollow root for breeding. Root weight showed a high broad-sense heritability and a low narrow-sense heritability. Average degree of dominance was 1.65, suggesting that its root weight is controlled by overdominance. Dominant genes had a positive effect on root weight. Hollow root occurrence expressed by a hollow area ratio showed a low broad-sense heritability and a low narrow-sense heritability. Average degree of dominance was 0.91, suggesting that hollow root occurrence is an incomplete dominant trait similar to a complete dominant trait. Dominant genes had a negative effect on hollow root occurrence. These findings indicate that the F₁ hybrid is effective for breeding a bigger root in ‘Sakurajima daikon’. However, hollow root is susceptible to environmental factors, suggesting that we need to consider environmental effects when selecting for hollow root-resistant lines.

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Methods of propagating and storing fern sporophytic plants through encapsulation of the callus in gel beads were examined. Morphogenetic potential callus were induced from an axillary bud of a fern, Ceratopteris thalictroides cultured on MS medium containing 3% sucrose and 10⁻⁵ M BA solidified with 0.2% Gelrite. Sporophytic plants were regenerated from subcultured callus, when transplanted to BA-free medium. Callus pieces were encapsulated in arginate gel beads with or without preculture on regrowth medium. Callus tissues prepared by encapsulation and stored at 20 or 30°C for 28 days successfully germinated and regenerated to sporophytic plants. Thus, encapsulation appears to be a technique that could be used for the stable propagation of in vitro cultures of fern sporophytic plants and for the storage of horticulturally important or endangered germplasm of ferns.

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We studied the water consumption of ‘Kyoho’ grape at each growing stage to develop a simple and practical irrigation program for the soil-mound rhizosphere restricted culture in a plastic house to reduce the load on the environment. It was considered that any management by tensionmeters would be difficult due to the uneven water content in the soil-mound and the large fluctuation in the water content depending on the location of the tensionmeters in the plastic house. A correlation of y = 0.250x was observed between the solar radiation intensity (x: MJ·m⁻²·day⁻¹) and water consumption (y: L·day⁻¹/tree). Average water uptake (AWU) per m² leaf area on fine days was 1.3 L at flowering, 1.0 L as the berry enlarged, and 1.3 L at the ripening stage, respectively. AWU did not differ in relation to the growth stage on cloudy/rainy days. Suitable amounts of daily irrigation were investigated. By controlling the daily irrigation based on the water consumption of the grapes and the amount of solar radiation, annual irrigation could be reduced by 46 to 47% of the conventional irrigation method based on the tensionmeter, proving the efficiency in lowering the load on the environment while producing high quality grapes.

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We investigated the effects of flower bearing types and pinching methods on the characteristics of water consumption in winter-spring harvest cropping type of carnation (Dianthus caryophyllus L.) in order to develop liquid fertilizer management of cultivation by fertigation. The standard type ‘Nora’ and spray type ‘Barbara’ were cultivated by bottom fertigation with single pinching or double pinching. The amount of daily water consumption changed with cultivation time, the amount of daily water consumption was lowest in summer for the early cultivation time and greatest in spring for the later cultivation time. The total amount of water consumption for ‘Nora’ grown by single pinching was 32.29 L (per plant), that of ‘Nora’ grown by double pinching was 35.26 L, that of ‘Barbara’ grown by single pinching was 29.75 L and that of ‘Barbara’ grown by double pinching was 30.29 L. There was a positive correlation between the amount of water consumption over 4 weeks and the number of leaves during those 4 weeks. There was a positive correlation between the amount of daily water consumption and the daily integrated solar radiation 4 weeks after planting. The amount of water consumption (y: L·plant⁻¹·4 weeks⁻¹) could be estimated by a regression line between the integrated solar radiation (X₁: MJ·m⁻²·4 weeks⁻¹) and the leaf number at that time (X₂: per plant) as follows; y = 0.00697X₁ + 0.00930X₂ − 1.36616, regardless of cultivar or pinching methods. Moreover, the amount of water consumption could be estimated by solar radiation alone starting 12 weeks after planting.

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The ‘packed bag-fertilization’ method of controlled-release fertilizer for tomato cultivation was investigated using a root-proof capillary wick watering system. This method facilitates removal of residual fertilizer before the soil is reused. The granules of fertilizer were packed in a water-permeable bag, which was placed on a wick in the soil. In this experiment, packed fertilizer (PF) was compared with mixed fertilizer (MF). Medium-fruited type of tomato plants were grown for 132 days from September to February up to the 7^th truss. There was no difference between PF and MF in plant height, whereas stem diameter at decapitation was smaller in PF than in MF. Fruit yield per plant was 2.1 kg in PF and 2.4 kg in MF. At the end of the experiment, the fertilizer bag was removed from the soil and analyzed. Elution percentages of total-N, P₂O₅, K₂O, CaO and MgO were 60, 40, 50, 50 and 30, respectively. The nutrients in soil after removing the bag were also analyzed. There was no increase in the concentration of any nutrient components during cultivation, indicating that there was no nutrient enrichment in the soil, although the amount of total-N in MF soil increased. Therefore, the soil used in PF has high reusability. The total amounts of nutrient decrease in soil were smaller in PF than in MF. It seems that the low vegetative growth and yield in PF is due to a lower elution rate of fertilizer from the bag. In conclusion, PF should be enhanced the elution rate of fertilizer during the early growth stages in order to improve fruit yield in the later growth stages.

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Effect of changing the environmental factors in a greenhouse covered with double-layered air inflated plastic film (air-inflated greenhouse) on the growth and fruit yield of cucumber in semi-forcing culture was investigated. To determine the advantages, an air-inflated greenhouse was compared with a standard type plastic greenhouse (normal greenhouse). The room temperature, ground temperature and relative humidity were higher, but the solar radiation was lower in the air-inflated greenhouse than in the normal greenhouse. The growth and yield of cucumber were improved in the air-inflated greenhouse. The lower vapor pressure deficit observed in the air-inflated greenhouse increased the stomatal conductance. So the higher room temperature and relative humidity, and the lower vapor pressure deficit increase the photosynthetic rate which improved the yield in the air-inflated greenhouse. The double-layered air inflated greenhouse was effective for both reduction in fuel consumption and increase of fruit yield.

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We designed a new labor-saving net aimed at preventing birds and animals from damaging bunches of table grapes on spur-pruned grapevines. The bag-like nets perfectly cover only the grape bunches, allowing many bunches to be quickly protected all at the same time; moreover, because the nets are easily hung beneath the trellis, workers do not need to use stepladders or other such implements. We investigated the efficiency of working with these prototype nets and the degree of protection from bird and animal damage. The time required to install the prototype nets was 32.8% of the time required to install standard commercial netting. We confirmed that the prototype nets almost completely prevented bird and animal damage in two cultivars. Furthermore, there were no undesirable effects of the prototype nets on fruit quality. These findings suggest that using this type of net is an effective method of preventing bird and animal damage to grape bunches on spur-pruned grapevines.

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To determine the sowing and transplanting date to produce a sufficient yield of immature black soybean (Glycine max L. cv. ‘Tankuro’) as a pre-culture crop for summer spinach (Spinacia oleracea L.), we sowed seeds of the soybean plants on various dates (from February 25 to April 9), and compared the plant growth and yield of each crop. The vegetative growth of the soybean plants stopped by the flowering date. To increase the yield of ‘Tankuro’ cultured in the spring, it was therefore important to increase the vegetative growth between sowing and flowering. Because the average temperature in the unheated greenhouse where the plant plug seedlings of soybean were transplanted greatly affected the vegetative growth of the soybean plants, yields differed greatly among years and sowing dates. Our analysis of 3 years of yield and temperature data revealed that a mean temperature of more than 18.8°C in the greenhouse from transplanting to flowering was required to yield 100 kg·a⁻¹ of pods containing two or more seeds. In practice, it would be desirable to transplant soybean after April 15 to avoid low temperatures that would prevent the plants from yielding 100 kg·a⁻¹ of pod weight.

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Experiments in 2007, 2008 and 2009 confirmed that a single application of 14.7 ppm of NAA to ‘Fuji’ apple trees during the stage of fruit cell division reduced fruit cracking in the stem cavity. In two of the three years the experiment was conducted, it was found that NAA application two weeks after full bloom reduced fruit cracking. However, it also caused a reduction of fruit weight at harvest and sometimes inhibited shoot elongation. On the other hand, when NAA was applied three or four weeks after full bloom, fruit cracking was reduced in each of the three years without adverse influence on either fruit quality or shoot elongation. It was suggested that the reduction of fruit cracking when NAA is applied during the stage of fruit cell division is related to a decline in the fruit growth rate during the stage of rapid fruit growth, due to the reduction in cell numbers.

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To promote flowering of Primula × polyantha Mill., cold storage was applied to seedlings in continuous darkness. When the seedlings of three cultivars were chilled to 0°C for 30 days till the end of August, all but the early cultivar flowered earlier. The seedlings of ‘Seventy Blight Pink’ were chilled to 0, 5, or 10°C for 15 or 30 days. Flower bud differentiation of the seedlings chilled to 10°C occurred earlier than that of those chilled to 0°C. The seedlings chilled to a higher temperature for a longer duration flowered earlier. However, their leaf widths and flower diameters were small when the seedlings were chilled to 10°C for 30 days. The seedlings chilled till the end of August flowered normally although a high proportion of those chilled till the end of July failed to show normal flowering. Based on these findings, it was considered optimal for the seedlings to be chilled to 0°C for 30 days till the end of August. Furthermore, the seedlings flowered earlier than those chilled to 0°C for 4 weeks without showing any decrease in leaf width, when they were chilled in a temperature combination of 0°C for 1 week and 10°C for 3 weeks, or they were chilled to 10°C for 4 weeks after foliar application of daminozide (1,600 ppm).

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Purple asparagus is becoming popular among consumers in Japan because of its unique appearance, thickness, sweetness, tenderness of the spears, and quality of vitamins and minerals. The growing area for purple varieties such as ‘Purple Passion’ is spreading, particularly in cool regions of Japan. However, lower yields compared to those of major green varieties have been regarded as a serious problem. Therefore, some growers hesitate to cultivate the purple varieties. In order to improve the yield of ‘Purple Passion’, we investigated the effect of high density planting on mother fern cultivation between 1999 and 2005. The yield of plots with a normal planting of ‘Purple Passion’ was lower than that of ‘UC157’ which is a green asparagus variety cultured in Japan. However, the yield of ‘Purple Passion’ in the plot with dense planting showed yields as high as those with normal planting of ‘UC157’. The spear weight of ‘Purple Passion’ in all treatments was larger than that of ‘UC157’, although the number of harvested spears of ‘Purple Passion’ per unit area was decreased compared to that from a normal planting of ‘UC157’. This advantage might contribute to labor-saving. These findings suggest that ‘Purple Passion’ can achieve a sufficient yield when cultivated by dense planting. The aptitude for dense planting and its unique properties are key factors in achieving stable cultivation and promoting the consumption of purple varieties in Japan.

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We investigated the effects of plastic house cultivation, temperature and day length during late autumn on induction of endodormancy in the Japanese pear ‘Gold Nijisseiki’. The plastic house cultivation advanced the initiation and development of flower bud by about 20 days compared with that under open-field cultivation. However, the plastic house cultivation was hardly effective in the induction and development of endodormancy of either flower or leaf buds. The potting experiment demonstrated that the lack of chilling inhibited the induction of bud dormancy, but the 16 hours photoperiod did not prevent dormancy induction. Temperature of 5°C was effective for inducing leaf bud endodormancy in the cuttings, whereas a temperature of 15°C was in effective. Leaf bud ABA concentrations in open-field cultivated ‘Gold Nijisseiki’ were increased with the induction of endodormancy by chilling in mid-November. However, the ABA concentrations in un-chilled plants were lower. In conclusion, the endodormancy of the Japanese pear ‘Gold Nijisseiki’ was mainly induced by low temperatures in autumn.

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The influence of dropping impact sustained before storage on occurrence of rot and rind disorder of stored lemons was examined. On dropping test, the incidence of rot and rind disorder was closely associated with impact energy. The rate was dependent on the area of impact, with impact on the fruit apex inducing the most rot generation. We measured all impact that lemon fruit received throughout the entire harvesting and processing procedures and investigated the incidence of rot and rind disorder in stored lemons. Most shock was induced by falling into the collecting plate at the end of the sorting line, and subsequently during the brushing and drying process. The amount of impact occurring during truck transportation and discharge at the packinghouse was not especially high. The rate of incidence of fruit rot increased with the length of the sorting line. A rot incidence model was constructed to predict the incidence of rot in lemons during sorting using storage time and impact energy as variables. The simulated and the measured incidences of rot showed a high correlation. It was thought that rot generation after harvesting could be controlled by reducing the shock, but sustained by the fruit, the reduction was not sufficient. Therefore, it was suggested that technology to control rot generation could be established by combining prestorage conditioning and packaging films.

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For characterization of chemical and/or physical taste evaluation of Japanese bunching onion (welsh onion), the relationship between sensory descriptions of pungency, sweetness and texture, and the chemical and/or physical properties were investigated. Pungency score of the fresh bunching onion and the amount of pungent precursors estimated by pyruvic acid production showed a strong positive correlation (r = 0.94**). Sweetness score of the heated bunching onion and brix value did not show a positive correlation, while the concentrations of glucose, fructose, total free sugar, and sucrose equivalent sweetness showed a good agreement with the sweetness score (r = 0.98** to 0.99**). Texture scores (scores of organoleptic hardness) of boiled and grilled bunching onion showed a strong positive correlation with the penetration resistance measured by cylindrical plunger (Φ3 mm) (r = 0.90* to 0.99**). As shown above, pungency and hardness of the bunching onion can be expressed as the amount of pyruvic acid and penetration resistance, respectively. The sweetness should be estimated by the concentrations of glucose, fructose, total free sugar, and the sucrose equivalent sweetness, but not the brix value.

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Day-to-day fluctuations in the sugar contents of cucumber fruits harvested at the same greenhouse were investigated. The fruits contained glucose and fructose in almost equal quantities. The contents of the glucose (and fructose) in the fruits fluctuated between 0.8% and 1.4%, dependent on the date of harvest. A relationship was shown between glucose contents in the fruit and the weather on the day before harvest; shorter duration of the sunshine or shading treatment decreased the glucose contents of fruit harvested the next day. Because the sugar contents of cucumber fruits varied day-to-day, it is useful to measure the sugars in the fruits simply and rapidly in order to obtain cucumbers of high quality. A disposable blood glucose sensor (biosensor) was used to measure a glucose in the fruits. The results obtained by the biosensor showed high correlation with the data on glucose obtained by capillary electrophoresis. Because the sample preparations were very simple and it took less than 10 min to obtain the results, this method using the biosensor appears to be quite effective for the rapid measurement of the glucose contents in cucumber fruits.

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As a peach rootstock, ‘Hidakokufubenishidare’ was selected from local ornamental peach trees in Kokuhu-cho, Takayama city, Gifu prefecture, Japan, and registered for the Seed and Seedling Law of Japan in 2008. It was characterized by drooping, low tree height and double flowers with red petals. The maturation period was from late September to early October which was about 150 days after full bloom. It bears small clingstone fruits of 35 g and frequently contains double seeds. ‘Hidakokufubenishidare’ seedlings have high graft compatibility with major peach cultivars. When used as rootstock, death and trunk injury in young plants are suppressed compared to major rootstock varieties such as ‘Ohatsumomo’ or ‘Nagano-Yaseito’. Furthermore, tree vigor of budwoods is weaker and development of tree crowns is slightly slower than the major rootstock varieties. In trees using seedlings of this cultivar as rootstock, yields up to the 6th year are slightly lower than those using the major rootstock cultivar ‘Nagano-Yaseito’, but the fruit quality is equivalent. This new cultivar is suitable as a peach rootstock in cold areas, where death and trunk injury in young plants occur frequently because of freezing.

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New everbearing strawberry cultivars, ‘Natsuakari’ and ‘Dekoruju’ for summer and autumn production were registered in 2007. ‘Natsuakari’ was selected from hybrid seedlings between a female parent ‘Summerberry’ (everbearing) and a male parent ‘Kitanokagayaki’ (June-bearing). The fruits of ‘Natsuakari’ are very tasty and sweet. Its taste is superior to any other everbearing cultivars and is as good as high quality June-bearing cultivars. Its fruit shape is uniform and storability is high. The berry is suitable for strawberry cakes, and for fresh eating also. ‘Natsuakari’ is adapted not only to summer-autumn production but also to forcing culture. ‘Dekoruju’ was selected from hybrid seedlings between a female parent ‘Pajaro’ (June-bearing) and a male parent ‘Morioka No. 26’ (everbearing). Since the fruits of ‘Dekoruju’ are very firm, their storability is very high. The fruits are uniform, very shiny and tasty. The berry is suitable for strawberry cakes. ‘Dekoruju’ has field resistance to powdery mildew. It is adapted to summer-autumn production in cool climate regions. Seedlings of ‘Natsuakari’ and ‘Dekoruju’ are available from seed companies in Japan.

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