Cucumber (Cucumis sativus L.) and melon (C. melo L.) are globally important crop species in the family cucurbit. However, pests and disease, including various viral diseases, affect cucumber and melon production in Japan. Choosing a resistant cultivar is one of the most effective methods for disease control. Many sources of viral resistance have been identified in cucurbits, and various resistant commercial cultivars have been bred. This review describes the present status of cucurbit breeding and sources of resistance to the four major viruses in Japan. Melon yellow spot virus (MYSV) and Cucurbit chlorotic yellows virus (CCYV) are devastating insect-transmitted viruses that were first reported in Japan. MYSV-resistant cucumber and CCYV-resistant melon were selected from germplasm collections. The resistance of cucumber accession 27028930 to MYSV is temperature dependent and intermediate; melon isolate (MYSV-S) inoculation resulted in no systemic infection of resistant cucumber plants at low temperature (20°C). The melon accession JP 138332 exhibits high resistance to CCYV. These accessions are considered promising sources for breeding resistant cultivars. Cucumber green mottle mosaic virus (CGMMV) and Melon necrotic spot virus (MNSV) are soil-borne viruses. The Korean melon accession ‘Chang Bougi’ is resistant to the SH isolate of CGMMV. The resistance of ‘Chang Bougi’ is controlled by two independent complementary recessive genes (cgmmv-1 and cgmmv-2), whereas resistance to MNSV is controlled by a single recessive gene (nsv) in melon. The nsv gene was introduced into commercial cultivars, and these cultivars have shown high resistance to MNSV. There is an increasing demand for new cultivars with resistance to additional viruses. To satisfy this demand and solve problems related to cucurbit viruses, core collections of each cucurbit crop are required for the identification of resistant germplasm, and marker-assisted selection will allow us to breed new cultivars rapidly and accurately.

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In acid citrus, genetic control of male sterility, an important characteristic for breeding seedless fruit cultivars, is not precisely known because of the presence of barriers such as polyembryony and a long juvenile phase. In this study, 22 crosses with 16 male-fertile acid citrus cultivars were carried out and the zygotic seedlings were grafted onto adult satsuma mandarin trees to enhance flowering. Four crosses with two monoembryonic and male-sterile citrus plants (HY16 and ‘Kiyomi’) were also carried out and zygotic seedlings showing precocious flowering were used to examine the inheritance of male sterility. Of the 26 crosses, 21 with six cultivars as seed parents generated male-sterile and male-fertile zygotic seedlings with various segregation ratios, whereas five crosses with ‘Sudachi’ as a seed parent generated only male-fertile zygotic seedlings. The sterile anthers were categorized into undeveloped and underdeveloped by their size in most progenies. The result of these crosses showed that eight cultivars with male-sterile cytoplasmic factors of ‘Yuzu’, lemon, or satsuma mandarin generated male-sterile zygotic seedlings, while ‘Sudachi’ with male-fertile cytoplasmic factors of pummelo generated only male fertile zygotic seedlings. The result also suggested that a dominant nuclear fertility-restorer gene system comprising one epistatic gene R₁ and two complementary genes R₂ and R₃ controls the restoration of male fertility and male-sterile anther size in acid citrus plants with sterile cytoplasm (S). The complementary gene R₃ is located downstream from R₂, and gene R₁ is epistatic to R₂ and R₃ genes. Genotypes (S)r₁r₁r₂r₂-- are responsible for undeveloped anthers while genotypes (S)r₁r₁R₂-r₃r₃ are responsible for underdeveloped anthers. The identified genotypes for male sterility in major acid citrus cultivars will contribute to breeding seedless acid cultivars.

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Shoot growth and fruit production of ‘Masui Dauphine’ fig trees (Ficus carica L.) were compared between a novel training method and a control method, with various tree spacing. In the novel training, the shoots were elongated downward from a horizontal limb at 180 cm height, whereas control training had upward growing shoots from a horizontal limb at 40 cm height. Sprouted shoots of the novel training trees leafed a few days earlier than controls. The difference in training did not significantly affect longitudinal growth (the internode length and leaf area) of the shoots but, on the apical portion of the shoots, the shoot diameter and leaf weight per area in novel training were less than in controls. Many lateral shoots sprouted on the shoots of the novel training in autumn. The novel training prevented failure of fruit set, which was observed on the basal portion of control shoots with excess vigour owing to narrow tree spacing. The novel training promoted coloring of fruit on the basal portion of the shoots and depressed it on the apical portion. The size and weight of fruit tended to be reduced on the shoots that underwent novel training. The observed characteristics of novel training may be due to the change of lighting conditions and reduced photosynthetic rate due to downward shoot positioning.

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The self-incompatible (SI) Japanese pear cultivar ‘Kosui’ was pollinated with pollen collected from a chronically gamma-irradiated ‘Kosui’ tree, and a progeny was obtained. This progeny resulted in the identification of self-compatible (SC) breeding selection, designated 415-1, which showed 74.4% fruit set in a self-pollination test. PCR-based genetic analysis revealed that 415-1 has S-RNase genotype S₄S₅, which is the same as that of the parent, ‘Kosui’. Pollination trials were used to investigate whether 415-1 harbors a stylar-part mutation or a pollen-part mutation in its SI locus. When 415-1 was pollinated with pollen from cultivars of the same genotype (‘Syuugyoku’ and ‘Oushuu’), no seed-containing fruit were set, indicating that 415-1 contains functional S₄- and S₅-RNase alleles. On the other hand, when ‘Syuugyoku’ and ‘Oushuu’ were pollinated with pollen from 415-1, fruit-bearing seeds were produced; therefore, we conclude that 415-1 carries a pollen-part mutation at the SI locus. This new self-compatible breeding selection will be useful for the development of new Japanese pear cultivars with SC.

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The present experiments were undertaken in order to clarify the effects of a high potassium fertilization level on the occurrence of viviparous sprouting in melon fruit. Melon (Cucumis melo L. group) plants of two susceptible lines and one resistant line to viviparous sprouting were used at two different potassium concentrations. A high potassium fertilization level (12.0 mmol·L⁻¹) resulted in a marked decrease of the occurrence of viviparous sprouting in the susceptible lines, and in the increase of the endogenous ABA content. No significant differences were observed in the seed number per fruit, the seed weight, and the percentage of seed germination at a high level of potassium fertilization. Further experiments were conducted in order to analyze the effects of exogenous ABA treatment at a low potassium fertilization level (1.5 mmol·L⁻¹) on the occurrence of viviparous sprouting in melon fruit. At 25 days after pollination, ABA solution at different concentrations was sprayed on the fruits of the susceptible melon line grown at two different potassium fertilization levels. Even at a low potassium fertilization level, exogenous ABA application inhibited the occurrence of viviparous sprouting and increased ABA contents both in juice samples around the placenta and in the seeds. ABA treatment, however, led to a significant decrease in the seed number per fruit and in the percentage of seed germination, as a result of a marked increase in the ABA content and potassium absorption.

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Variations in the dormancy and early flowering ability of seedlings of four populations of Lilium longiflorum, Yaku Shima (LYA), Kikai Jima (LKI), and Ishigaki Jima (LIS) in the Ryukyu Archipelago, Japan and Pitouchiao (LPI), Taiwan, and two populations of L. formosanum, Wulai (FWU), Taiwan and a domesticated Fukuoka population (FFU), Japan were investigated. Seedlings of each population were grown at 15°C for five months. They were then transplanted into an experimental open field for two years or at 15, 20, 25, and 30°C under natural day length for 22 weeks. In the field experiments, FWU, FFU, and LPI populations continued to develop new leaves even at >30°C. Flowering percentage for FFU and LPI was 90% and 19.7%, respectively. Leaf development of LIS, LKI, and LYA was completely arrested from early June in both years, and the flowering percentages were 28, 25, and, 10 in the second year, respectively. Under controlled temperature conditions, LKI and LYA populations produced new leaves only at 15°C. FFU and LPI continued growing at 25 and 30°C, whereas the other populations did not grow. FFU significantly produced the heaviest leaves and bulbs and the highest number of scales per bulb at any temperature. The results showed that high temperature induces bulb dormancy in northern L. longiflorum. Strong correlation with the early flowering ability and bulb dormancy was also found. It seems that the early flowering ability of L. formosanum is largely dependent on the lack or reduction of bulb dormancy after adaptation to the local southern climate. The latitudinal variation of this trait demonstrated the geographic gradient during species habituation in the Ryukyu Archipelago.

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In senescing carnation (Dianthus caryophyllus L.) flowers, ethylene production begins in the gynoecium, and the resulting ethylene acts on petals, inducing autocatalytic ethylene production. We investigated the role of abscisic acid (ABA) in ethylene production in the gynoecium of flowers. First, cDNAs of major genes involved in ABA biosynthesis and signaling were cloned from carnation flower tissues. Then, changes in ABA content and gene expression of ABA biosynthesis and signaling in the ovary were examined using three cultivars, ‘Light Pink Barbara (LPB)’ and ‘Excerea’, whose cut flowers produce ethylene during senescence and have an ordinary vase-life of about one week, and ‘Miracle Rouge’, whose cut flowers produce no detectable ethylene during senescence and have a vase-life of about three weeks. ABA content in the ovary was 530–710 pmol·g⁻¹ fresh weight (FW) from Os 2 (early opening stage) to Os 6 (end of opening stage) in ‘LPB’, and at 200–380 pmol·g⁻¹ FW in ‘Excerea’ at the same stages; but 930 pmol·g⁻¹ FW at Ss 1 (early senescence stage). The ABA content remained at 70– 160 pmol·g⁻¹ FW in ‘Miracle Rouge’. The changes in ABA content were in parallel with the transcript levels of DcNCED1 (carnation gene for 9-cis-epoxycarotenoid dioxygenase). DcPYR1 (ABA receptor gene) transcript was 0.004–0.007 relative expression level (r.e.l.) in ‘LPB’ ovary at Os 1–Os 3, and 0.028 r.e.l. at Ss 1 (beginning of senescence stage). In ‘Excerea’ ovary, DcPYR1 transcript was 0.025–0.037 r.e.l. during flower opening and higher at Ss 1. By contrast, DcPYR1 transcript remained at 0.002–0.006 r.e.l. in ‘Miracle Rouge’ ovary during flower opening and senescence. The transcripts of DcACS1, the key gene for ethylene biosynthesis, were detected at Ss 1 in ‘LPB’, and at Ss 2 in ‘Excerea’, but not in ‘Miracle Rouge’ throughout flower opening and senescence stages. These findings suggest that ABA plays a causal role in inducing the expression of the DcACS1 gene in the gynoecium, leading to ethylene biosynthesis, and that both the ABA content and DcPYR1 expression must be above putative threshold levels for ABA to exert its action.

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Children of school age spend a large part of their daily lives not only at home but also at school. The present study surveyed the possible health benefits of indoor plant intervention on the indoor environment for 15 students in 6 classrooms (4 classrooms with indoor plants and 2 classrooms without indoor plants) in 2 newly built elementary schools in Seoul, South Korea. Symptom degree of building-related illness was evaluated as sick school syndrome according to indoor plant placement. An observation of the air temperature of the classrooms for 3 months after indoor plant placement did not find a change in the classroom at School A but detect a decrease in the classroom at School B with or without indoor plants. Formaldehyde concentration in indoor air reduced with time spent in the classrooms at both schools, and was not affected by indoor plant placement. After 3 months, volatile organic compounds showed high concentrations in the classrooms without indoor plants but demonstrated low concentrations in the classrooms with indoor plants only at School B. In the comparison of the symptom score, there was a constant decrease in the classroom with indoor plants but not in the classroom without indoor plants. However, multiple regression analysis showed that the subjective symptom degree of sick school syndrome had little relation to indoor plants.

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To investigate the relationship between the development of floral buds and the expression pattern of floweringrelated genes, observation of floral organ development and expression analysis of RpFT, RpSOC1, RpLFY, RpTFL1, RpCEN, and RpAP3 were carried out from July to August 2011 of the evergreen azalea ‘Oomurasaki’. After floral meristem development, floral organs, such as sepals, petals, stamens, and carpels, were observed subsequently on the floral meristems. The expression level of RpTFL1 gradually decreased with floral meristem development; however, the expression level of RpFT and RpLFY increased continuously until carpel development and that of RpAP3 began to increase with stamen development. RpSOC1 and RpCEN showed an irregular expression pattern during floral bud development. These results suggest that the period of floral organ development can be determined by the expression pattern of RpTFL1, RpFT, RpLFY, and RpAP3 in evergreen azalea ‘Oomurasaki’.

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A mixture of xyloglucan oligosaccharides (XGO) was prepared from xyloglucan (XG) of tamarind seed gum by digestion with Aspergillus recombinant XG-specific xyloglucanase and subsequent purification by ethanol fractionation. The XGO mixture contained XG7, XG8, and XG9 at the ratio of 1 : 4 : 5, which was almost identical to the literature value of constituent subunits ratio of 1.2 : 3.8 : 5. The XGO mixture at 1% promoted flower opening in carnation (Dianthus caryophyllus L.) cultivars, such as ‘Pure Red’ and ‘Lillian’. On the other hand, there was no effect on other cultivars, such as ‘Collin’, ‘Light Pink Barbara’, and ‘Mule’. Promotion of flower opening by 1% XGO was exhibited earlier than that by glucose or sucrose at 1% in ‘Pure Red’ carnation. Separate application of XG7 or XG9 stimulated flower opening in ‘Pure Red’ carnation, suggesting that all the constituents in the XGO mixture were effective in stimulating flower opening. Based on these observations, the mechanism of action of XGO on carnation flower opening and its future practical use as a flower-opening agent are discussed.

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