Strawberries grown under low nitrogen during floral transition develop a normal dichasial cyme. However, in ‘Ai-Berry’, the shoot apical meristem flattens and develops into fasciated inflorescences when floral transition is suppressed by rich nitrogen and high temperatures in early autumn. In greenhouses, the fertility of pistils and pollen decreases for various reasons, but normal and well-shaped fruit production can be achieved by introducing pollinators. When a flower bud develops under excessive nitrogen, the number of rows (whorls) of pistils on the receptacle increases, so the occurrence of “catfaced berries” and “tip-green (white) berries” increases in ‘Ai-Berry’. In addition, if vegetative growth becomes too vigorous due to excessive fertilization or GA₃ treatment, boron and/or calcium translocation to the flower buds is suppressed, and “abnormal flowers” in ‘Hokowase’, “poorly fertilized berries” in ‘Tochiotome’, and “tip-shrunk berries” in ‘Sagahonoka’ develop along with tip burn of newly emerging leaves and sepals. The greening of pistils (“phyllody”) is caused by mycoplasma infection, similar to hydrangea, but another symptom of phyllody, transformation to sepal-like organs, is not caused by mycoplasma, but by high temperature during pistil differentiation. It is considered that “seedy” is caused by insufficient translocation of boron during fruit enlargement, and “tip softening” is caused by a lack of photosynthate during fruit ripening.

Kaki-shibu is made from astringent types of persimmon fruit, with none made from non-astringent types. We have produced Kaki-shibu using the PCNA (pollination constant and non-astringent) type of persimmon when fruits have high tannin levels as well as astringent-type fruits. We expected to obtain a new material of Kaki-shibu from PCNA fruits, since PCNA fruits have different chemical properties regarding tannins compared with astringent types. In this study, we focused on how the differences in chemical properties of these kaki-shibu affect their biological activities, such as antioxidation and α-glucosidase inhibition, using each Kaki-shibu made from PCNA ‘Fuyu’, PCA (pollination constant and astringent) ‘Atago’, and PVA (pollination variant and astringent) ‘Hiratanenashi’. The results showed that the total polyphenol content of PCNA ‘Fuyu’ was comparable to that of non-PCNA with no significant difference, when the same weight of freeze-dried samples was prepared from Kaki-shibu and dissolved with the same amount of distilled water. Kaki-shibu from PCNA ‘Fuyu’ showed marked DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, as well as that from PCA ‘Atago’ and PVA ‘Hiratanenashi’. Furthermore, Kaki-shibu from PCNA ‘Fuyu’ also showed high α-glucosidase inhibitory activity by non-competitive inhibition, the same as Kaki-shibu from astringent types. These results suggest that Kaki-shibu made from PCNA ‘Fuyu’ is also reliable for commercial use instead of Kaki-shibu made from astringent types. However, Kaki-shibu from PCNA ‘Fuyu’ did not show activity as high as Kaki-shibu from astringent types based on an oral glucose tolerance test using an ICR mouse, probably due to the higher sugar contents in Kaki-shibu of PCNA ‘Fuyu’. Further investigation is needed to evaluate their functionality in vivo.

Inheritance of muscat flavor, a typical grape berry flavor, is controlled by several loci. A QTL in linkage group (LG) 5 was identified by several previous QTL analyses as a major muscat QTL. A total of 36 cultivars and a selection including muscat cultivars released in Japan were genotyped using four SSR markers: Nifts5-50910, Nifts5-50929, Nifts5-50937, and VVII52, located near QTL. We found that an SSR haplotype (LG5-Hap1) was harbored by all cultivars with muscat flavor. This haplotype was inherited from ‘Muscat of Alexandria’ to ‘Neo Muscat’ to ‘Kaiji’ to ‘Hakunan,’ and then to ‘Shine Muscat.’ Cultivars harboring LG5-Hap1 were also genotyped as muscat-type by the previously reported CAPS marker linked to the muscat trait. Overall, 145 grapevine plants that were produced by 75 crosses at NARO were divided into a group with muscat flavor and a group without the flavor. The ratios of selections with LG5-Hap1 were compared between the two groups. The proportion harboring LG5-Hap1 in the muscat group was significantly larger than that in the non-muscat group. All individuals with berries that were constantly evaluated as muscat throughout the evaluated years harbored the haplotype. Although the genotypes at other QTLs need to be muscat-type to breed grapevine plants with muscat flavor, the SSR polymorphisms defined as LG5-Hap1 as well as the CAPS marker may be used as DNA markers for muscat grapevine breeding.

This experiment was conducted with the aim of establishing a technique to preserve the original strain by creating a seed strain using tissue culture. For the test material, the tip side, base side, and petiole of undeveloped and developed leaves of 1- and 2-yr-olds were also tested. The expanded 1st-year leaf-petiole plot produced the highest number of somatic embyros. We developed an effective acclimatization method that involved aseptic pre-acclimation in a liquid medium with vermiculite as the support, and then transplanted the culture onto a urethane mat for hydroponics. As a result, the survival rate increased to about 80%. When gibberellic acid was applied to plants that had lost their leaves during hydroponic acclimatization, the next leaf foliated from the buds. The morphology of plants was similar to that of 2-yr-old plants. The number of individuals that developed new leaves increased with a rise in concentration of sucrose added to the liquid medium. After 4 plantlets were planted in a planter, 2 of the 4 plantlets survived until the following year, and 1 of them flowered and set fruits, yielding 7 seeds.

We investigated the influence of the blooming stage, different parts within the petal, and dark treatment on adventitious bud formation in Chrysanthemum morifolium ‘Jimba’ petal tissue culture. In this petal tissue culture, the percentage of adventitious bud formation can be increased by culturing the central part of petals from fully-bloomed flowers after L-Kynurenine treatment in the dark for 10 days. It is suggested that adventitious bud formation involves endogenous plant hormones present in petals. The fact that adventitious buds occurring on the petal after 35 days of tissue culture did not arise from calli suggests that the level of mutation of adventitious buds formed is low.

In recent years, freezing injuries of chestnut trees have become more frequent with the increase in new plantings of chestnuts. Furthermore, global warming may accelerate the increase in freezing injuries of chestnut trees. In this study, we aimed to elucidate meteorological factors that affected the occurrence of freezing injuries of chestnut trees from the viewpoint of the effects of year-to-year differences (Exp. 1) and orchard locations (Exp. 2). At first, in Exp. 1, we examined relationships between meteorological factors (temperature and precipitation) and freezing injuries of chestnut trees in Kasai, located in Hyogo Prefecture, over the past 11 years. A positive correlation was recognized between the minimum temperature in January and degree of damage, minimum temperature in January and tree death rate, and mean temperature in January and degree of damage. Years with warmer average temperatures in January tended to have more freezing injuries. Next, in Exp. 2, we examined to elucidate relationships between freezing injuries (change of freezing tolerance) and several meteorological parameters including the temperature, precipitation, soil water, and water contents of current shoots in 7 different locations in Hyogo Prefecture. The degree of freezing tolerance of buds of the current shoots was positively related to the minimum temperature, but not the precipitation or soil moisture. However, even if the minimum temperature was the same, a difference in freezing tolerance of buds of the current shoots was observed. Reasons for this may be that trees have been transplanted from mountain hills and rice fields, and the soil has a low air ratio, and a high compactness. It was also suggested that when sunshine conditions are good, or when livestock compost or base application is applied during the winter, the freezing temperature rises and may lead to freezing injuries.

The effect of planting density on dry matter production was investigated in the cultivation of spinach for processing, which is grown more sparsely than for fresh use. Dry matter production was analyzed based on the fraction of radiation intercepted (f_i-SR), amount of radiation intercepted (DIR), and radiation use efficiency (RUE) of a spinach canopy grown at a row spacing of 30, 35, or 40 cm and a plant spacing of 5 or 10 cm. The light absorption coefficient, representing the relationship between f_i-SR and the leaf area index (LAI), did not differ depending on the planting density, and LAI determined DIR. Although there was no significant difference of RUE by planting density in 2021, the value with the 10 cm planting interval was significantly higher than that with the 5 cm due to late snowing and a rapid decline in the temperature. Dry weight per unit ground area was significantly higher with the 5 cm plant spacing than with the 10 cm spacing during growth. However, no significant difference was observed at harvest. Until f_i-SR was saturated, a higher dry weight yield depended on the high DIR caused by the increase in LAI arising from dense planting. After f_i-SR became saturated, the increase in dry matter depended on RUE, and the difference in dry matter accumulation became relatively small. A spacing of approximately 10 cm between plants could produce spinach with traits suitable for processing and commercial use while maintaining a yield equivalent to that of dense planting with a spacing of approximately 5 cm.

A spring-sown onion trial was conducted in different soil areas in the same geographical area. The harvest date of onion grown in gray lowland soil was four to ten days earlier than that in andosol, depending on the onion variety. Throughout the study period from seedling to harvest, plants in the lowland area showed vigorous growth in height and number of leaves before bulb enlargement, and bulb enlargement in the lowland area was earlier than in the andosol area. In addition, the average daily soil temperature in the lowland area during the mid-growth stage in June was high. ANOVA was conducted for the year of cultivation and soil treatment of ‘Momiji No. 3’, which revealed that the lowland area significantly influenced the increase in bulb weight and bulb diameter. Furthermore, considering the physical properties of soil, the lowland had higher bulk density and solid phase distribution than andosol. The distribution of the liquid phase was higher in andosol, indicating that the moisture content was higher in this soil type. It was hypothesized that the higher moisture content in andosol prevented an increase in soil temperature by evaporation, resulting in growth differences. While this study investigated the influence of environmental factors such as soil variation and meteorological data on crop growth, future research should focus on both environmental and genetic factors to fully clarify the onion bulb enlargement process.

Flowering control of field-cultivated summer-to-autumn flowering chrysanthemums was established using light culture and selecting appropriate cultivars. In order to make the technique applicable in wider areas, we attempted to stabilize the period from light-off to anthesis. The effects of natural day-length after light-off on flowering were studied. Long days, especially near the summer solstice in the northern part of Japan, inhibited floral development of some cultivars selected in mid-latitude regions. We characterized and selected cultivars suitable for light culture and that flower stably under longer photoperiods. The use of cultivars with a longer critical day-length for flowering could reduce the delay of anthesis.

In this study, we determined the appropriate ripening conditions for early harvesting, and analyzed the phenotype and gene expression of 「Shonan Pomoron Red」 a tomato bred in Kanagawa Agricultural Technology Center. Tomatoes harvested at the breaker stage ripened at various temperatures, and the results showed that accumulation of lycopene was promoted by 20–25°C ripening treatments. Gene expression levels of phytoene synthase (PSY) and carotenoid isomerase (CRTISO) were also higher at similar temperatures. On the other hand, at 5 or 35°C, the level of lycopene accumulations was low. Fluorescent lamp irradiation also increased accumulations of lycopene and β-carotene, and accelerated fruit coloration. Moreover the expression of carotenoid biosynthesis-related genes was also increased indicating that fluorescent lamp irradiation activates the carotenoid biosynthesis pathway. These results indicate that the appropriate ripening temperature and light irradiation of 「Shonan Pomoron Red」 can affect lycopene and β-carotene accumulations and expressions of carotenoid biosynthesis-related genes at phenotypic and gene expression levels.