The gaseous plant hormone ethylene plays an essential role in a number of developmental processes, including seed germination, seedling growth, leaf and petal abscission, fruit ripening, and senescence. 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is a key enzyme in the ethylene biosynthetic pathway, and its activity increased in response to endogenous and exogenous factors. In fruit, different ACS isogenes are induced and are responsible for differences in ethylene production among cultivars. ACS is phosphorylated in vivo, and phosphorylation confers protein stability. Ethylene is perceived by ethylene receptors, many of which have been identified and are known to be negative regulators of ethylene signaling. This review focuses on transcriptional and post-translational regulation of ACS. Furthermore, the effect of ethylene on the stability of ethylene receptors in apple is described.

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The field performance of ‘Fuyu’ and ‘Hiratanenashi’ Japanese persimmon (Diospyros kaki Thunb.) trees grafted onto rootstocks propagated from cuttings of root suckers of dwarfed trees (R-a and R-b) was investigated over seven years. The results were then compared with the performance of trees grafted onto seedling stocks (S) as well as that of micropropagated and own-rooted trees (O-R). Shoot growth of both cultivars on R-b was less vigorous than that on R-a, while tree height of ‘Hiratanenashi’ on R-a was the same as that of both S and O-R. Secondary shoots on R-b trees were scarce in both cultivars in the fifth and sixth years. On R-b, both cultivars bore flowers soon after field establishment and thereafter continued to do so abundantly, with the percentage of flower-bearing shoots on R-b trees being the highest for each study year. Yield efficiencies calculated by units of trunk cross-sectional area, canopy area, and canopy volume showed that R-b trees produced fruit most effectively, although the total yields during the three harvest years were not significantly different between rootstocks. The appearance of the graft union with R-b varied depending on the scion cultivar, but no union was damaged by the occurrence of several typhoons, which uprooted a number of trees. These results show the possibility of using R-b propagated by cutting as a dwarfing rootstock for persimmon trees. Overall, the R-b rootstock improved yield efficiency, although fruit quality requires further investigation because it is thought to be affected by rootstock type.

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The locations of the 18S-5.8S-25S ribosomal RNA gene (rDNA) in the seedlings of Japanese pear [Pyrus pyrifolia (Burm. F.) Nakai] ‘Osa Gold’ and European pear (P. communis L.) ‘La France’ and the 18S ribosomal rDNA in ‘Osa Gold’ were determined using fluorescence in situ hybridization (FISH). 18S-5.8S-25S and 18S rDNA probes were labeled with biotin-16-dUTP. The probes were detected using a fluorescein isothiocyanate (FITC)-avidin conjugate with chromosomes counterstained with propidium iodide (PI). The 18S-5.8S-25S and 18S rDNA sites of ‘Osa Gold’ and the former of ‘La France’ were detected in telomeric positions of six chromosomes. The number and positions of rDNA sites were stable.

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In this study, we aimed to characterize which factors control ethylene production and fruit drop in persimmon (Diospyros kaki Thunb.). We determined the effects of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU; a specific photosynthesis inhibitor) and defoliation treatments on the photosynthetic rate, transpiration rate, sap flow, fruit drop, and ethylene evolution. DCMU treatment, which prevented photosynthate transport but allowed water flow, promoted fruit drop by 67% 10 days after treatment. Defoliation treatment, which prevented both photosynthate and water transport, significantly hastened fruit drop. On average, fruit drop occurred 2 days earlier with defoliation treatment than DCMU treatment. Compared with the control, treated fruit attached to the tree showed an increasing trend in ethylene production, although at a low level (≤ 0.8 nL · g⁻¹ · h⁻¹ in the flesh; ≤ 20 nL · g⁻¹ · h⁻¹ in the calyx). Fruit abscission is thought to be induced by a following ethylene burst, because fruit showing an abscission trend showed high rates of ethylene production (almost 200 nL · g⁻¹ · h⁻¹). Thus, blocking photosynthate transport and water flow induced initial and autocatalytic increases in the production of ethylene, which plays a crucial role in triggering fruit drop. Overall, our results suggest that the transport of photosynthates, or both photosynthates and water, to fruit inhibits fruit drop by preventing the induction of ethylene synthesis in young persimmon fruit.

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In order to develop a new male-sterile line of eggplant (Solanum melongena L.), the F₁ rootstock ‘Assist’ (Solanum aethiopicum Aculeatum L. Group × S. melongena ‘DMP’) was continuously backcrossed to S. melongena ‘Uttara’ using ‘Uttara’ as a recurrent pollen parent up to BC₄ generation. All examined F₁ ‘Assist’ produced pollen grains while BC₁ plants segregated into male fertile and sterile plants. The male-sterile plant did not produce any pollen grains. BC₂, BC₃, and BC₄ progenies obtained from male fertile backcross progenies were segregated into male fertile and sterile plants and each segregation ratio fitted 3 : 1. BC₃ and BC₄ progenies obtained from male-sterile backcross progenies were fixed to male-sterility without segregation. Selfed progenies of the male fertile BC₂ progeny were segregated into male fertile and sterile plants and the segregation ratio fitted 15 : 1. Therefore, the pollen non-formation characteristic is assumed to be a form of cytoplasmic male-sterility (CMS), induced by incompatibility between the cytoplasm of S. aethiopicum Aculeatum Group and the nucleus of S. melongena. Further, these segregation results indicated that two independent dominant fertility restorer (Rf) genes control the fertility restoration of this CMS. High values of fruit set, number of seeds per fruit, and the seed germination rate found in BC₄ progenies indicate that the cytoplasm of S. aethiopicum Aculeatum Group has no notable negative effect on seed fertility of S. melongena. A new male-sterile line of eggplant could be developed by utilizing the cytoplasm of S. aethiopicum Aculeatum Group.

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The shapes of flowers and the cross-compatibility of Curculigo latifolia, which produces a taste-modifying protein, neoculin, were investigated for the purpose of setting fruits in Japan as a resource of neoculin. C. latifolia is an andromonoecious plant, that is, flowers in a lower position in an inflorescence are hermaphrodite with long styles, although flowers in higher positions are staminate with short styles. This shows that 22% of all flowers were hermaphroditic in an inflorescence. By the hand-pollination study, the largest rate of setting C. latifolia fruits was shown by the 5th day from the first flowering. The rates of fruit set were gradually reduced after that day. The number of fruits peaked by the 13th day from first flowering. On the other hand, the rate of fruit setting was shown to be 45% by cross-pollination and 4% by self-pollination. These results indicate that C. latifolia has self-incompatibility. To improve the rate of fruit setting of C. latifolia, it is necessary to pollinate compatible pollen by around the 15th day after the first flowering.

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Sweetpea (Lathyrus odoratus L.) is an important ornamental crop belonging to the Fabaceae family. In Japan, commercial cut flower production under forced culture has flourished, but few cultivars are bred exclusively for cut flower forced culture. In order to obtain knowledge for the selection of breeding materials, we elucidated the genetic relationships among eighty-seven sweetpea cultivars and two related species using the amplified fragment length polymorphisms (AFLP). Sweetpea cultivars were grouped into two clusters. Cluster I consisted of four cultivars, including a wild cultivar, ‘Cupani’ and cultivars established from spontaneous mutation or natural hybridization, such as ‘Cupid’ and ‘Painted Lady’. The biggest cluster, cluster II, consisted of eighty-three sweetpea cultivars. No distinct subcluster shared common morphological or ecological characteristics, such as tendril-less, plant type, or flowering habit in cluster II. The distinct genetic differentiation among cultivars highly seems to reflect sweetpea breeding history originating in the United Kingdom 300 years ago using limited genetic resources. Thus, hybridization with genetically distinct, exotic resources may contribute to the development of sweetpea cultivars.

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The effect of L-2-aminooxy-3-phenylpropionic acid (AOPP) on bud formation was investigated by determination of total phenolics in explants and medium browning in the micropropagation of the epiphytic orchid Neofinetia falcata (Thunb.) H.H. Hu. Explants, upper portion of plantlets, were cultured on a medium containing 0, 0.01, 0.1 or 1.0 mM AOPP. Browning was decreased from 70% to 3% by increasing AOPP concentration up to 1.0 mM. All surviving explants developed buds at 0, 0.01 and 0.1 mM AOPP. The highest mean number of buds (7.2) was produced on medium containing 0.01 mM AOPP. Multiple buds were formed on the explants 8 weeks after planting and multiple shoots had developed after 12 weeks. Total phenolics continuously increased in control explants up to 2.03 mg · gFW⁻¹ after 4 weeks. In contrast, in explants treated with 0.01 mM AOPP, total phenolics ceased to increase for 4 weeks of culture and remained at 1.46 mg · gFW⁻¹, but thereafter increased to 2.24 mg · gFW⁻¹, the same level as the control, after 8 weeks. Medium browning continuously increased in the control, whereas medium containing 0.01 mM AOPP showed little browning after 4 weeks of culture and thereafter increased to the same degree as the control. The present results suggest that 0.01 mM AOPP is the most suitable concentration to control browning and bud formation in N. falcata.

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Factors involved in delayed flowering and the formation of abnormal capitula in four summer-to-autumn flowering cultivars of Chrysanthemum morifolium Ramat. were investigated. Anomalous involucral bracts, i.e. bracts formed among ray and disc florets within the capitulum, were more frequent in ‘Floral Yuka’ plants grown at day/night temperatures of 20/12.5°C than at 20/20°C under a 12 h day length or natural day length of 14–15 h. The number of involucral bracts in the capitulum of plants grown at either 35/25°C or 25/15°C increased compared with that of plants grown at 30/20°C under a 12 h day length. A natural long day length suppressed flower bud development and promoted the formation of many involucral bracts in the capitulum, compared with inflorescences of plants grown under a 12 h day length. Long day length of 14–15 h induced anomalous involucral bract formation in ‘Floral Yuka’ and ‘Iwa no Hakusen’. In contrast, high temperature promoted involucral bract formation in the capitulum, primarily in ‘Seiun’, and neither day length nor temperature affected involucral bract formation in ‘Natsubiyori’.

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Time-course changes in the elasticity index (EI) of 8 cultivars and 1 selection of grape berries on vines were investigated with a nondestructive acoustic method. A portable device was constructed for the measurement of grape firmness. The EI was determined by the formula EI = f₂² · d², where f₂ and d were the second resonant frequency and the diameter of the sample respectively. In all cultivars, the date of veraison was judged by touch and the EI largely decreased around veraison. These changes were classified into two types; one decreased before veraison and the other after veraison. The EI was compared with the firmness measured by two penetration methods. Relationships between the EI and firmness measured by the penetration methods were classified into three types of regression curves; a linear relation which detected similar berry firmness with both the nondestructive method and the penetration methods; logarithmic, in which the nondestructive method was more sensitive when berries were hard; and exponential, in which the nondestructive method waas more sensitive when berries were soft. We concluded that these differences were caused by differences in the spatial softening process.

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