Interspecific graft-chimeras between leaf mustard (Brassica juncea) and red cabbage (B. oleracea var. capitata cv. Ruby Ball) were generated by in vitro grafting. Leaf morphological investigation confirmed that the individuals derived from the chimeras by axillary bud culture were periclinal chimeras whose three apical cell layers were the HHR or HRR type. PCR detection confirmed that the periclinal chimeras shared the DNA polymorphisms of their donor plant. Leaf and flower morphological characteristic analyses of the periclinal chimeras suggested that trichome formation and calyx coloring were derived from the first cell layer (LI) of the apical meristem, while the pinnate leaflet, petaloid stamen formation, and peduncle coloring were from the second cell layer (LII) in Brassica. Furthermore, a propagation system for the periclinal chimeras was established by combining axillary bud and soil-less cultures.

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Most persimmon (Diospyros kaki Thunb.) cultivars bear only female flowers, which limits persimmon cross-breeding. Although the genetic and molecular bases of sexuality in persimmon have yet to be determined, a maleness-associated region, DlSx-AF4S, was recently identified in D. lotus L., which is a wild diploid relative of hexaploid/nonaploid D. kaki. This finding suggests that D. lotus has a heterogametic male (XY-type) dioecious sexual system. Here, we investigated the association between DlSx-AF4S genotypes and the maleness (sexuality) of 174 persimmon cultivars. DlSx-AF4S was detected in all but three cultivars that bear male flowers, suggesting that the maleness of persimmon is controlled by a genetic factor similar to that in D. lotus. On the other hand, DlSx-AF4S was also found in 17% of the tested cultivars that were reported to bear only female flowers. Considering that the sexuality of persimmon is more susceptible to environmental factors, some cultivars may hardly bear male flowers under certain conditions even though they have male determinants. In addition, a higher ploidy level in persimmon may also complicate sex expression. This elusive sex expression system in persimmon will be better understood when a male determinant(s) linked to DlSx-AF4S is identified and characterized in the future.

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The establishment of a method for citrus cultivar identification is required to protect domestic citrus producers and breeders’rights. In order to establish a scientific method for citrus cultivar identification with marked reliability, it is necessary to develop appropriate DNA markers. Accordingly, this study aimed to establish such a method based on CAPS markers to realize expedient cultivar identification. Thirty-three citrus cultivars and breeding lines were genotyped using nine CAPS markers and the results obtained. The data constitute a source of basic information for the identification of domestic citrus cultivars. Using the genotyping data, we computed the smallest marker set that can distinguish between all 33 cultivars and breeding lines. This showed that all cultivars and breeding lines could be identified using eight CAPS markers. The genotyping data were also used to perform parentage analysis of seven cultivars bred in Japan. This analysis revealed that ‘Shiranuhi’ was not the male parent of ‘Kanpei’. Further analysis strongly suggested that ponkan was the male parent of ‘Kanpei’.

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The effects of the nitrogen application rate of substrates and concentration of nutrient solution in hydroponics on the growth of rooted cuttings were investigated in Elatostema involucratum Franch. & Sav. The rooted cuttings were potted in vermiculite containing 0, 200, 400, or 800 mg per L of nitrogen fertilizer. The growth of transplants was similar in all concentrations 21 days after being potted. However, the growth of transplants with 400 mg per L was more favorable than that of the others 42 days after being potted. The rooted cuttings were grown hydroponically with a concentration of 0.25, 0.5, or 1 unit of standard nutrient solution. With 0.5 and 1 unit, death or leaf tip drying of transplants was observed. The optimal growth of transplants was observed with a concentration of 0.25 units.

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‘Akita-Oni-Shibori’ is an F₁ hybrid developed from the inbred fixed lines of ‘Matsudate-Shibori’, a native Japanese radish variety. Although ‘Akita-Oni-Shibori’ is an F₁ hybrid of related lines, it shows heterosis in its yield characteristics, such as the leaf weight, root weight, and T-R ratio, compared with its parental inbred lines. On the other hand, ‘Akita-Oni-Shibori’ does not show heterosis in its morphological characteristics, internal characteristics of the root, or component characteristics (content of isothiocyanate and sugar), indicating its acquisition of dominant or additive effects. Compared with the original cultivar ‘Matsudate-Shibori’, ‘Akita-Oni-Shibori’ exhibits marked uniformity in its morphological characteristics and internal characteristics of the root. In addition, high-level uniformity even in its component characteristics (content and composition of isothiocyanate and sugar) has been confirmed. These suggest that the development of the F₁ variety is effective for achieving the commercialization of ‘Matsudate-Shibori’. On the other hand, native ‘Matsudate-Shibori’ has diverse genetic resources and it is necessary to continue preserving them.

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Cypripedium macranthos var. rebunense is an endangered wild orchid in Japan. We have developed two kinds of propagation method for this orchid: an aseptic culture method through protocorm-like bodies (PLBs), and a fungi-utilizing culture method using a symbiotic fungus. Plants propagated using the two methods have been grown in our botanic garden, and now nearly 100 plants bloom every year. Using these propagated C. macranthos var. rebunense plants, we examined the differences in growth and flowering traits between aseptically- and symbiotically-cultured plants. Symbiotically-cultured plants grew vigorously and produced more flowers than aseptically-cultured plants. The survival rate at six years after potting was 94% for symbiotically-cultured plants, while that of aseptically-cultured plants was 42%. Flowering occurred depending on the plant size and not on the plant age: plants which were heavier than 10 g in fresh weight and developed 3–4 leaves at more than 10 cm were able to produce flower buds. Consequently, we propagated seedlings by symbiotic culture using fruits obtained from the cultured plants. Thus, a sustainable cultivation system for this endangered orchid, which is completely independent of plants in their natural habitat, was successfully established.

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We investigated the influence of the placement and amount of the applied calcium superphosphate on the early growth of direct-sown onions (Allium cepa L.) on Andosols. The effect of localized fertilizer application was compared with broadcast application. The placement of calcium superphosphate below the onion seed may affect the early growth of onions, especially in the early growth stage. Fertilizer placed 0 to 4 cm below the seed was more effective than broadcast application. Seedling emergence based on the amount of calcium superphosphate 0 cm below the seed was not affected by the amount of calcium superphosphate in our experiment. The soil solution EC value of localized calcium superphosphate did not affect seedling emergence. These results suggest that the most effective placement of phosphatic fertilizer is directly below the seeds, and the effective amount to be applied is 30 or 45 kg・10 a⁻¹ as P₂O₅.

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To clarify factors which contribute to fruit yield in low-truss tomato cultivation, we investigated the effects of the planting stage and density of seedlings on transplantation on the growth, fresh fruit yield, and yield components. Tomato seedlings were transplanted at four seedling stages, and at two planting densities. Seedlings with 2–3 leaves (Direct planting, no secondary raising), immediately before anthesis in the first inflorescence, at the first flower anthesis, or at the 3rd flower anthesis were transplanted onto rock wool slabs at 2.6 or 3.9 plants per m². Significant differences in the fruit yield, leaf area index (LAI), and total dry matter production (TDM) were observed among the seedling stages and densities at 110 days after sowing. However, neither the seedling stage nor plant density significantly influenced the light use efficiency (LUE). Since the difference in LAI caused the difference in the fraction of light interception by plants, the fraction mainly influenced the yield and TDM. These results were also supported by Pearson’s correlation between each yield component. TDM had positive correlations with dry fruit yield and fraction of light interception. There was a significant positive correlation between the fractions of light interception and LAI. Accordingly, the differences in fruit yield and TDM would be mainly due to the fraction of light interception resulting from the difference in LAI. These suggest that there is no improvement of LUE on modifying the seedling stages and densities at transplantation, and that increases in LAI and the fraction of light interception would increase the fresh fruit yield on low-truss tomato cultivation.

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We investigated the effects of grafting Cucurbita maxima Duchesne ex Lam. cv. Kurokawa-delicious plants onto rootstocks of Cucurbita moschata Duchesne ex Poir. cv. Shima-kabocha on growth and yield under high-temperature conditions, and analyzed the bleeding rate based on the root pressure and the relative water content in leaves. The self- and cross-grafted plants of Kurokawa-delicious were planted in a glasshouse in early July (average temperature: 29.1°C). In plants grafted onto Shima-kabocha rootstocks, main stem elongation and leaf development were improved, and the harvested fruits weight per plant was significantly higher compared to that of self-grafted plants. Plants grafted onto Shima-kabocha rootstocks and grown in pots in the glasshouse for 11 days in late August (average temperature: 28.5°C) had a higher bleeding rate per unit root dry weight than self-grafted plants, suggesting that physiological activity in the root systems of Shima-kabocha rootstocks was higher. In self-grafted plants grown for 4 days under a temperature regime of 35/30°C (day/night), the relative water content of leaves was significantly lower than in plants grown at 25/20°C, whereas in plants grafted onto Shima-kabocha rootstocks, the relative water contents at 35/30°C and 25/20°C were similar, and greater than that of self-grafted plants grown at 35/30°C. Thus, the greater activity in the root system and higher relative water content in leaves of plants grafted onto Shima-kabocha rootstocks could maintain a high photosynthetic rate, resulting in improved growth and yield under high-temperature conditions.

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The study was started for the purpose of making Madonna lily (Lilium candidum L.) one of the commercial horticultural crops in Japan. From seed germination through to the growth of seedlings and first cropping of bulbs, 15°C and 19°C were optimal and a high temperature of 27°C or more was not suitable. Abscisic acid (ABA) had little influence on seed germination at optimal temperatures. With respect to the prevention of germination inhibition at the supraoptimal high temperature, fluridone treatment was effective, but gibberellin (GA₃) did not have an effect. The meristem of the secondary (daughter) bulb, which initiated and grew at the base of the flowering stem of the primary (mother) bulb, started to be lifted up in mid- or late-September. The shoot apex of the secondary bulb did not stop initiating vegetative primordia until flower differentiation. Around November a new meristem of the third (grand daughter) bulb differentiated at the base of the elongating stem axis in the daughter bulb. From next March onward, the stem of the daughter bulb elongated more rapidly and its apex shifted to the flower initiation phase. Flowering occurred from late May to early June. On the other hand, the initiation and filling of scales continued in the third bulb. Therefore, the bulb consisted of scales of three generations, until about August, when the last of the primary mother scales were consumed. Not only initiation of the leaf primordia in the apical meristem of the bulb but also the elongation and unfolding of new leaves (apical foliar part of foliage scale) above ground were continued and radical leaves existed in all seasons in Madonna lily. Therefore, Madonna lily did not have a dormancy state such as shown by Easter lily (L. longiflorum Thunb.).

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We investigated the effects of methods to train lateral branches on the growth and yield of parthenocarpic eggplant ‘Shota’ to increase profitability on forcing culture. Three different lateral branch training methods based on maintaining a different number of leaves per flower (fruit) were examined. The growth rate of primary scaffold branches was faster when two leaves were left above each flower as compared with those when one or no leaf was left. Total numbers of marketable fruits and total fruit yields on leaving two or one leaf were larger than when leaving no leaf, and the values from April to June were the largest when two leaves were left for each flower. It was also shown that the total fruit yield on leaving two leaves above each flower in ‘Shota’ was larger than the value on conventional lateral branch training in the non-parthenocarpic eggplant ‘Chikuyo’.

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We aimed to determine an appropriate choice of rootstocks and scions for raising fig (Ficus carica L.) nursery stocks within the current year by softwood grafting. The combinations for grafting were based on ‘Masui Dauphine’ as scions and ‘Ischia Black’ or ‘Negronne’ as rootstocks resistant to ceratocystis cancer disease. The cuttings were collected from dormant shoots of the rootstock cultivars at different times (December and March), and were divided into separate (basal, medium and apical) portions. At the end of March, the cuttings were placed in water or planted in a pot of soil. Growth of the cuttings was influenced by the stem portion, but not by the time of collection. The cuttings collected from the basal position leafed later but rooted earlier, and achieved their required shoot length (0.3 m) earlier than those collected from the apical position. The early grafting improved the grafting success rate. The proportion of surviving grafted nursery stock was higher when using the immature portion of a ‘Masui Dauphine’ scion shoot than a semi-mature portion.

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