Nagabo-natsuhaze (Vaccinium sieboldii Miq., 2n = 2x = 24), which is designated as critically endangered (CR), is a Japanese endemic Vaccinium species. In order to use it as a breeding material for blueberries, we carried out in vitro chromosome doubling of multiple shoots in two lines (M3 and M15) of Nagabo-natsuhaze. Furthermore, we investigated the morphological characteristics of tetraploids induced by these treatments. Multiple shoots were aseptically treated with two antimitotic agents, oryzalin and colchicine, at different concentrations and times. The survival rate of colchicine-treated shoots tended to decrease with increasing treatment time, whereas the survival rate on oryzalin treatment differed between M3 and M15. M3 showed high survival rates (over 90.0%) of colchicine-treated shoots regardless of the concentration and time. In those of M15, the survival rate tended to decrease with increasing treatment time. When the ploidy levels of the new shoots obtained from colchicine and/or oryzalin treatments were analyzed by flow cytometry, various polyploid shoots such as tetraploid and ploidy chimera (2x + 4x and 4x + 8x) were obtained in both treatments. Among the treatment conditions tested in the present study, tetraploid induction by colchicine treatment occurred in 3 of 9 treatment conditions in M3 and in only 1 treatment condition in M15. In the case of oryzalin treatment, on the other hand, tetraploid shoots were induced more than with colchicine treatment in both lines. Especially, the tetraploid induction rate in both lines reached its highest (10.0%) on treatment with 0.005% oryzaline for 24 h. Moreover, these tetraploids had large leaves, flowers, and pollen, which are typical traits of other tetraploid plants, and produced pollens that could be stained with acetocarmine.

To clarify the effects of ultrafine bubble (UFB) water irrigation on dry weight (DW) allocation and nitrogen uptake efficiency of pot grown two-year-old ‘O’Neal’ southern highbush blueberry (Vaccinium corymbosum L.), a destructive investigation and ¹⁵N-tracer method were carried out. The trees were irrigated with UFB water or tap water daily by hand irrigation. ¹⁵N-labeled ammonium sulfate was applied on April 19, May 25, and July 24 during the 2018 growing season, and the labeled trees were destructively harvested 2 weeks later for DW measurements, atom% of ¹⁵N, and N content of each of the plant organs. The first destructive investigation showed no difference in DW of each organ between treatments; however, the ¹⁵N content of fine roots was significantly higher with UFB treatment. The second and third destructive investigations showed the significant promotion on not only underground but also aboveground organ DW allocation with UFB treatment. The ¹⁵N content of the third destructive investigation showed a consistent result with an increase of DW with UFB treatment. In July, DW and ¹⁵N content of underground organs and summer shoot were significantly higher, resulting in a significant elongation of the total shoot length per tree. These results suggest that UFB treatment promoted nitrogen absorption and further supports the growth of aboveground organs. We have demonstrated for the first time that UFB water irrigation can enhance the physiological activity of roots, thus improving nitrogen absorption, in blueberry.

To improve the yield of greenhouse cucumbers in Japan, we investigated the effects of environmental elements on yields of cucumber grown in environmentally controlled greenhouses. Several cultivars of the cucumber were grown in 2 greenhouse compartments. In the conventional compartment, only the air temperature was controlled. In the controlled compartment, the air temperature, humidity, and CO₂ concentration were controlled. In total, 3–5-month experiments were conducted 6 times for 3 years, and yields were compared between the conventional and controlled greenhouses. Although air temperatures were controlled at the same settings in both greenhouses, in half of the experiments, the temperatures differed significantly between the conventional and controlled greenhouses. Relative humidity and humidity deficiency in the controlled greenhouse were significantly higher and lower, respectively, than those in the conventional greenhouse. The CO₂ concentration in the controlled greenhouse was significantly higher than that in the conventional greenhouse in 3 experiments conducted in the winter season. Cucumber yields in the controlled greenhouse were significantly higher than those in the conventional greenhouse in 4 experiments but there was no difference in 2 experiments. The yield was strongly correlated with average daily solar radiation in the greenhouses. The yield per unit solar radiation was positively and strongly correlated with the daytime CO₂ concentration in the greenhouses. Thus, the controlled CO₂ concentration improved the yield in the controlled greenhouse. However, there was no significant correlation between the yield per unit solar radiation and relative humidity or humidity deficit.

Experiments were performed to investigate the influence of daytime heating temperature on dry matter production and photosynthesis of tomato plants grown under low light conditions. The light use efficiency and dry weight of tomato plants increased significantly with a high daytime temperature when the light intensity was between 10 and 25 W・m^–2PAR. In actual cultivation, it was considered that the recommended daytime heating was a solar radiation intensity of 125 W・m^–2 or more. When the daytime heating temperature setpoint was raised from 20°C to 24°C in May with higher light conditions, the growth rate of tomato increased to develop more leaves and shorten the intervals of trusses. The photosynthetic rate of tomato plants grown at 24°C in the daytime was significantly higher than in those grown at 20°C, when examined at a light intensity not less than 200 μmol・m^–2・s^–1 (50 W・m^–2PAR). In addition, the number of leaves increased and intervals between anthesis were improved. In order to clarify the heat balance of daytime heating, the daytime heating load of the pipe framed greenhouse was determined in a region with low winter light conditions. The daytime heating load in a single span greenhouse located in Fukuoka Prefecture increased with a higher temperature setting, with heat loss from walls and roofs accounting for 82 to 89% of the total heat loss from the greenhouse. In addition, it was considered that the heating load for daytime heating could be calculated by subtracting the value of the untreated house from heat loss and soil heat flux of the heated house. The values of the monthly heating load were similarly high from December to February and relatively low in March in forcing culture of tomato. The total fuel consumption for daytime heating (heating temperature setpoint: 20°C) from December to March was estimated to be 1.20 L・m^–2. The amount of fuel consumption was the largest between 9 to 10 o’clock when heating was started, accounting for 20 to 30% of the total.

A continuous cultivation method for tomato as a new technique to increase yields using a plastic greenhouse with an eave height of 2 meters was developed. This method led to harvesting a total of 24 bunches in a year without year-round cultivation by combining 6–8 bunch pruning and intercropping 2–3 times. When the difference in the number of intercropping times was compared, the amount of light received by the leaves above the fruit cluster where the fruit grows during the low light intensity season is larger in the 4 intercroppings per year than in the 3 intercroppings per year. In addition, the average fruit weight and marketable fruit rates were improved, and the marketable fruit yield per unit area was increased. It became clear that more than 30 ton per 10 a yield was obtained by 6 bunches pruning with 3 times intercropping method.

Relationships among the length of shoots, number of flower buds attached to shoots, and distribution of starch grains in the shoots of rabbiteye blueberries were investigated. The growth of shoots to 20 cm in length was weak. The shoot length showed an increasing tendency with an increasing number of flower buds attached to the shoot until 80 cm in length. Storage starch grains were observed in the cortex, xylem, and pith of the shoot, and the density in the pith was higher than in other organs. There was a strong positive correlation between the shoot length and percentage of the pith area in the cross-sectional area of the shoots. Hence, to obtain a stable yield, using shoots from 30 to 70 cm in length as bearing shoots under conditions of the Kanto region of Japan is recommended. The results of this study also suggest that summer pruned vigorous shoots could produce high-quality berries if the length of shoots is controlled.

We developed an effective technique of spot replanting to promote early high yield in young trees of Japanese pear ‘Kosui’ and ‘Keisui.’ Planting 3 trees per stock and 1-main branch training promoted shoot growth. They increased lateral branches more than the usual 1 tree and 3-main branch training in 2–5 years young trees aged 2–5 years. As a result, the yield of young trees aged 3–5 years was high and lead to increases in growth and fruit quality in maturing orchards five years after replanting. This result suggested that 1-main branch training strengthens tree vigor more than 3-main branch training and increases lateral branches in early stages after replanting. It follows from this that the increase of lateral branches leads to early high yields when applying the pruning technique of using 1-year lateral branches. These results showed that 3 trees per stock and 1-main branch training effectively promted early high product spot replanting.

Lily bulbs of Oriental hybrid ‘Casa Blanca’ produced in Hokkaido or Niigata were packed in polyethylene bags with wet peat moss and subjected to pre-chilling at various temperatures for various durations from 0 to 20 weeks before storing at –2.0°C. On moving to –2.0°C, bulbs were dissected and the shoot length and Brix of shoot tip juice were measured. Soluble carbohydrate concentrations of the shoot tip were analyzed by a conventional extraction method using hot ethanol with HPLC. After storage at –2.0°C for more than 7 months, they were grown in a glass house kept at a minimum temperature of 15°C to check for the occurrence of black shoots, non-flowering plants, and damaged leaves, which might be caused by long-term storage at –2.0°C.

Rates of black shoots, non-flowered plants, and damaged leaves became high when bulbs were subjected to pre-chilling at 1°C for more than 12 weeks. The rise in rates and decrease of the sucrose content occurred simultaneously. Furthermore, changes in the sucrose content were closely related to changes of Brix.

When bulbs were pre-chilled at 1, 6, 8, or 12°C for 8 weeks followed by 1°C for 10 weeks, those pre-chilled at 1 or 6°C showed a decreased sucrose content or Brix at the end of pre-chilling and higher rates of non-flowering plants and damaged leaves after storage at –2.0°C for 24 weeks. An extended duration of storage at –2.0°C for 8 weeks induced black shoots and non-flowering plants when bulbs were pre-chilled at 1°C for 18 weeks before moving to –2.0°C.

From these results, it was concluded that excessively long pre-chilling of bulbs at low temperatures below 6°C induces black shoots and leaf damage after long-term storage at a subzero temperature.

Effects of daytime heating on yield, photosynthesis, translocation and distribution of photosynthetic assimilates of strawberry ‘Sagahonoka’ during the winter season in northern Kyushu were examined. Daytime heating at 18°C resulted in increases of the commercial fruit number and yield from December to February. The days from flowering to ripening of top fruits in the first and second inflorescences were shortened by about 5 days by daytime heating treatment. The photosynthetic rate was higher at 18°C than at 13°C when PPFD was 300 μmol・m^–2・s^–1 or higher. The translocation rate of ¹³C-photosynthetic assimilates under low light conditions was significantly higher at 18°C than at 13°C. On the other hand, the distribution patterns of ¹³C-photosynthetic assimilates were similar at 18°C and 13°C in the daytime. Since daytime heating increased the commercial fruit yield from December to February, it was indicated that daytime heating was effective for high productivity in winter strawberry forcing culture in northern Kyushu. Also, physiological factors promoting an increase in yield involved higher temperatures accelerating photosynthesis and translocation rates.

Hydrangea sepals show seasonal coloration change. They express red and blue as the summer color due to a delphinidin-based anthocyanin. Through changing to green color, they newly express red or purple as the autumn color. Recently, the horticultural value of Hydrangea expressing the autumn color has increased. We studied pigment biosynthesis and the coloration mechanism of autumn color expression. The pigments responsible for autumn color were cyanidin-based anthocyanins including cyanidin 3-lathyroside, which was newly detected as a main pigment of sepals in this study. The autumn color could not be expressed in shaded parts and was uniformly expressed even in sepals that display a marginal picotee pattern in the summer color. The pigment biosynthetic mechanisms of autumn and summer color expression differ in terms of the anthocyanin structure including chromophores, light requirement, and tissue specificity. In contrast, the coloration mechanisms of autumn and summer colors were similar; i.e., the blue color was generated by the formation of a chelate structure of aluminum ion by anthocyanin and 5-O-caffeoylquinic acid, while the red color was possibly generated by involvement of a compound that inhibits the formation of this chelate structure. This similarity causes the corresponding tone of autumn and summer colors in the same plant.

In this study, the relationship between Brix or acidity and characteristics of fruit was investigated in 7 citruses (‘Aoshima unshu’, ‘Shiranuhi’, ‘Setoka’, ‘Harehime’, ‘Seinannohikari’, ‘Tsunokagayaki’, and ‘Reikou’). In all 7 citruses, the height of fruiting affected Brix, and Brix was low when the transverse diameter of fruit was large. In decision tree analysis for Brix or acidity with all data on the characteristics of fruit, results differed among citruses. In decision trees for Brix of ‘Aoshima unshu’ and ‘Shiranuhi’, it was indicated that fruits with a high a* value of peel showed high Brix in juice. Also, in all citruses, fruits with low transverse or vertical diameters showed high Brix in juice. In the decision tree for acidity, it was indicated that transverse and vertical diameters affect the acidity of juice of citruses other than ‘Aoshima unshu’.

Concavities often develop on the scales of garlic bulbs stored for long periods in sub-zero conditions. Previous studies indicated that curing methods and the temperature and duration of sub-zero storage affect the occurrence of such concavities. In this study we histologically analyzed the developmental process of concavities to elucidate the causative mechanism. Striped depressions in a vertical direction were observed on the surface of the tip of garlic scales with mild symptoms. The depression parts expanded to near the base of scales in garlic with severe symptoms. Cell collapse was observed in a few cell layers near the epidermis in scales with mild symptoms. The more severe the concavity symptoms, the more cell layers showed collapse. No evidence of ice crystal formation was found in the internal tissue of scales with severe symptoms. This histological study suggests that the concavity on garlic scales is induced by factors other rather than ice crystal formation.

In this study, the effects of polyethylene (PE) wrapping and fruit size on fruit qualities and the occurrence of fruit disorders during storage for 3, 4, and 5 months at an ambient temperature were investigated in the citrus variety ‘Harumi’. On evaluating the effect of fruit size and PE wrapping, the occurrence of peel wrinkles was serious in small classes (M, L) without PE wrapping. However, it was markedly prevented by PE wrapping. In large classes (2L–4L), dehydration of flesh was observed in fruit without PE wrapping. On the contrary, the decrease of specific gravity and occurrence of dehydration of flesh were markedly prevented by PE wrapping. On testing the effects of the length and timing of PE wrapping, weight loss and the occurrence of peel wrinkles were prevented by PE wrapping regardless of the length and timing. In the tests of 3 or 4-month storage, Brix of the juice in fruit wrapped with PE in the second half of the storage period was higher than that wrapped with PE throughout the storage period. In the same treatment, the occurrence of rind wrinkles was lower than that without wrapping. These results indicate that the occurrence of fruit disorders can be suppressed and the fruit quality can be improved by storing fruit with PE wrapping in the citrus variety ‘Harumi’.

The development of a cultivar identification system for fresh and processed fruits is required to protect breeder’s rights regarding acid citrus cultivars and for the appropriate management of nursery plants for acid fruit cultivars because their fruits are mainly utilized for cooking and processing. A new set of 10 single nucleotide polymorphism (SNP) markers, which can be used to evaluate the allelic genotype on either locus of 9 citrus chromosomes, has been developed to reinforce the cultivar identification of major acid citrus by improving the previous system for fresh market cultivars. The new set of 10 SNP markers can discriminate the 85 examined citrus cultivars from each other, comprising 10 conventional acid citrus cultivars, 2 acid citrus cultivars released by Tokushima Prefecture and the National Agriculture and Bio-oriented Research Organization (NARO), and 73 fresh market cultivars. The parentage analysis of 10 SNP markers revealed no discrepancy in parent-offspring relationships of 43 combinations in the 85 examined citrus cultivars. They are applicable to SNP genotyping of fresh, and processed fruits such as peel, juice, squeezed vinegar and dry fruit of major acid citrus cultivars. The renewed cultivar identification system is a practical technology that is applicable to the rapid inspection at customs for goods infringing on intellectual property rights and will help protect breeder’s rights pertaining to the registered cultivars.

A new non-pungent sweet pepper cultivar, ‘Shishiwakamaru’, was developed. ‘Shishiwakamaru’ is a purebred cultivar selected by marker-assisted selection and continued backcross [(the sweet pepper cultivar ‘Kisyu Shishitou No. 1’ × the non-pungent sweet pepper cultivar ‘Kyohikari’) × ‘Kisyu Shishitou No. 1’]. This cultivar has the loss-of-function pun1 allele the same as that of ‘Kyohikari’. Pungent fruits were not observed at all by sensory tests. Capsaicin and dihydrocapsaicin contents in the fruits were not detected at all by LC/MS. Fruit size, external appearance, and yield were almost the same as those of ‘Kisyu Shishitou No. 1’.