Carotenoids are one of the most important pigments for petal coloration in the yellow to red range; however, knowledge of carotenoids in petals is relatively limited. To better understand flower carotenoids, we analyzed carotenoid composition, the expression of carotenogenic genes, and the relationship between pigment composition and petal color in petals of Compositae plants, including chrysanthemums. We found that petals of yellow-flowered chrysanthemums have a unique carotenoid composition, and that the formation of white petal color in chrysanthemums involves carotenoid degradation catalyzed by carotenoid cleavage dioxygenase (CmCCD4a). We also showed three routes to an orange petal color via carotenoid components in 9 Compositae plants. In addition, we identified (5Z)-carotenoids that contribute orange color formation in calendula petals. In this review, we summarize our studies on carotenoids in the petals of Compositae plants.

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Investigations were made into the effects of ethylene and jasmonate on gum formation of Japanese apricot fruit (Prunus mume Sieb. et Zucc.). We treated ‘Benisashi’ and ‘Nanko’ fruit that had been artificially wounded with a stainless steel needle and examined the relation between the formation of ethylene and gum accumulation. In addition, we treated ‘Benisashi’ fruit with ethephon, 1-methylcyclopropene (1-MCP), methyl jasmonate (JA-Me), ibuprofen, and aminoethoxyvinylglycine (AVG) to investigate the relation of these chemicals with gum accumulation. Artificial wounding induced ethylene evolutional though the gum formation was not necessarily induced. Treatment with ethephon and 1-MCP did not significantly affect fruit gumming induced by artificial wounding, whereas treatment with JA-Me accelerated gum formation. Note also that JA-Me treatment induced gum formation in intact fruit whereas ibuprofen treatment reduced gum formation. In contrast, AVG treatment did not affect gum formation of intact fruit. These results show that JA-Me expedites gum formation of Japanese apricot fruit. Moreover, ibuprofen treatment before the rapid mesocarp development stage significantly suppressed the percentage of gummed fruit.

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To make progress in columnar apple breeding, we constructed genetic linkage maps of the Co genomic region and identified useful DNA markers that enable correct and efficient selection of columnar-type seedlings in a practical columnar apple breeding program. Linkage maps of three mapping populations were constructed on the apple linkage group 10, and the Co gene was mapped on two populations, ‘Fuji’ × 8H-9-45 and ‘Fuji’ × 5-12786. Closely linked marker genotypes of SCAR₆₈₂, SCAR₂₁₆, CH03d11, and Hi01a03 were determined on 33 columnar-type cultivars and/or selections, and non-columnar-type cultivars contained 7 ancestral cultivars of apple breeding in Japan. A 174 bp fragment for primer Hi01a03 was amplified in all columnar-type cultivars, selections, and ‘McIntosh’, but was not detected in other ancestral apples. Amplified products of 682 bp for SCAR₆₈₂ and 177 bp for CH03d11 were detected in almost all columnar genotypes except for one selection, and ‘McIntosh’, but the products were not found in other ancestral apples. A 177 bp allele of CH03d11, characteristic of a columnar phenotype, was detected in all 170 columnar-type plants obtained from 18 crosses, suggesting that it is one of the most tightly linked DNA markers to the Co. These results indicated that CH03d11 was the most reliable marker to distinguish columnar and non-columnar phenotypes for the MAS system. In our two most advanced breeding selections, the Co gene-associated alleles of the original columnar mutant (‘Wijcik’) on CH03d11 (177 bp) and Hi01a03 (174 bp) remained, indicating that using these two breeding selections as Co donors in the breeding program, CH03d11 and Hi01a03 enable the selection of seedlings with columnar phenotype.

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We compared the changes of sugar content and titratable acidity throughout fruit development in two cultivars, ‘Russian Orange’ from subspecies (ssp.) mongolica and ‘Hergo’ from ssp. rhamnoides of sea buckthorn (Hippophae rhamnoides L.). In ‘Russian Orange’ fruit, glucose content increased remarkably from mid-July to early August, whereas the contents of fructose, sucrose and ethylglucose did not increase. In ‘Hergo’ fruit, the content of each sugar did not increase during fruit development. Fruit titratable acidity was low during early fruit development, then remarkably increased from mid-July to early August and decreased at harvesting time in both cultivars. The sugar/acid ratio in ripe fruit was 1.14 in ‘Russian Orange’ and 0.34 in ‘Hergo’, indicating that ‘Russian Orange’ fruit has better flavor. In tracer experiments using ¹⁴CO₂, ¹⁴C-sucrose was found to be the major sugar in the leaves and the stems, suggesting that sucrose is the primary product of photosynthate and a translocatable sugar in sea buckthorn plants. Ascorbic acid content in ‘Russian Orange’ fruit decreased during fruit development, while the content in ‘Hergo’ fruit was roughly constant. ‘Russian Orange’ fruit showed high L-galactose dehydrogenase (L-GDH) activity. In tracer experiments, ¹⁴C-ascorbic acid was synthesized from L-¹⁴C-galactose and D-¹⁴C-mannose. These results suggest that the mannose/L-galactose pathway plays a role in the synthesis of ascorbic acid in sea buckthorn fruit.

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The location of the 5S ribosomal RNA gene (rDNA) in species from six genera of the Citreae of Aurantioideae was determined using fluorescence in situ hybridization (FISH). A 5S rDNA probe was labeled with biotin-16-dUTP. The probe was detected using a fluorescein isothiocyanate (FITC)-avidin conjugate with chromosomes counterstained with propidium iodide (PI). When the chromosomes were observed under a G filter, PI-stained chromosomes were classified into the following five types based on the number and position of PI-positive (+) bands; B: one telomeric and one proximal band, C: two telomeric bands, D: one telomeric band, E: without bands and Dst: type D with a satellite chromosome. Two 5S rDNA sites were located in type D chromosomes in Citropsis gabunensis, whereas in Citrus reshni, Fortunella japonica, Clymenia polyandra and Swinglea glutinosa they were found in type E chromosomes. In Poncirus trifoliata, three rDNA sites were located together at the proximal PI (+) band of a type B chromosome, one site was located in the proximal region of a type D chromosome, and two sites were located together at the PI (+) band of a type D chromosome.

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Effects of high temperature (HT) on pollen quality, ovule fertilization and development of embryo and achene were investigated in relation to fruit malformation in ‘Tochiotome’ strawberry (Fragaria × ananassa Duch.). When the flower bud of the first inflorescence was developing, plants were transferred to HT (32/27°C) and control temperature (CT: 27/22°C) rooms. At anthesis, anthers were collected from flowers in the first (1st) and second (2nd) inflorescences to examine pollen viability and germination. Both viability and germination were not significantly different between the two temperatures and inflorescences. Approximately 90–93% of ovules were fertilized under CT in both inflorescences; however, the fertilized percentage of ovules in HT-1st was only 52% and significantly increased to 85% in HT-2nd. Embryo development in both inflorescences was accelerated by HT: embryos from HT regimes were in heart- and torpedo-shaped stages at 6 and 8 DAP while those of CT were still in globular- and heart-shaped stage. The transverse and longitudinal lengths of embryos under HT increased more rapidly than under CT. Embryo abortion in the globular stage was found at 2 and 6 DAP under HT-2nd. Relationships between the percentages of three types of achenes (unfertilized (Un), aborted (Ab), and normally developed (Nd) achenes) and degrees of fruit malformation were examined. Ripe fruits were graded into five fruit shape scores (0–4), 0 = well shaped fruit, and 4 = severely malformed. Nd achenes in CT-1st and CT-2nd were approximately 70% with fruit shape score; 0.8 and 0.2, respectively, whereas those in HT-1st and HT-2nd were 38 and 54% with high malformed shape score: 2.8 and 1.8. Un achene in HT-1st was 45%, while only 9% was found in HT-2nd. The Ab achenes rate was remarkably increased to 31% in HT-2nd treatment, these suggesting that the sudden rise of temperature after flower bud initiation lowered the ovule fertilization rate and raised the unfertilized achene rate, resulting in a high degree of fruit malformation in HT-1st, while longer HT increased achene abortion during early embryogenesis due to low pistil potential, and finally induced fruit malformation in HT-2nd.

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A Malaysian pepper accession, ‘LS2341’ (Capsicum annuum L.) is highly resistant to bacterial wilt (BW) caused by Ralstonia solanacearum E. F. Smith (species complex). Quantitative trait locus (QTL) analysis was performed using a double haploid (DH) population derived from a cross between the susceptible cultivar ‘California Wonder’ and ‘LS2341’. A linkage map was constructed using simple sequence repeats (SSRs) and amplified fragment length polymorphism (AFLP). The map spans 974 cM, and consists of 15 linkage groups (LGs). Growth chamber evaluations of BW resistance detected a QTL on LG 11. This LG corresponds to pepper chromosome 1 (P1). The QTL explained 33% of the resistance derived from ‘LS2341’, and was named Bw1. An SSR marker, CAMS451 was mapped in the centre of the QTL. Although BW-resistance is thought to be polygenically controlled, use of this linkage marker may improve the efficiency of breeding BW-resistant cultivars.

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Constant rooting by cuttings to raise seedlings at high temperatures during summer in a forced elevated bench culture system of strawberry is important. Abscisic acid (ABA) applied to crown tissue of cuttings of strawberry runner plants at higher temperature (30°C) without low temperature treatment (storage for 2 days at 5°C) stimulated rooting to the same level as at low temperature; however, naphtaleneacetic acid, gibberellic acid, and benzyl adenine did not stimulate rooting well. Sucrose synthase (SuSy) activity increased 1 day after starting ABA treatment at 30°C and 2 days after 5°C exposure. SuSy activity treated with ABA at 30°C was always higher than that without ABA at 30°C. Soluble acid invertase activity at 5°C increased at 1 day compared with that at 30°C, and the activity when treated with ABA at 30°C did not change compared with that without ABA at 30°C. Bound acid invertase activity showed no marked differences among crown tissues treated at 5°C, 30°C, and with ABA at 30°C. The content of ABA in crown tissue of cuttings at 5°C was compared with that at 30°C, but they showed only a slight difference. At high temperature, cuttings of strawberry runner plants produced roots by ABA without low temperature treatment.

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The thermotolerance and activation of antioxidant enzymes in the leaves of cucumber and tomato seedlings were induced by foliar application of H₂O₂. The induction of thermotolerance by foliar application of H₂O₂ was detected with decreased electrolyte leakage and malondialdehyde (MDA) content and increased water-soluble protein and chlorophyll content compared with heat-stressed seedlings. The levels of H₂O₂ and superoxide anions in the leaves of heat-stressed seedlings were also reduced by H₂O₂ pre-application before exposure to heat stress. The specific activities of ascorbic peroxidase (APX) and glucose-6-phosphate dehydrogenase (G6PDH) in the leaves of cucumber and tomato seedlings were significantly increased by foliar application of H₂O₂. The gel activities of superoxide dismutase (SOD), hydrogen peroxidase (HPX), and polyphenol oxidase (PPO) isozymes were abruptly increased by foliar application of H₂O₂ and these were maintained for 10 d afterward. The gel activities of guaiacol peroxidase (GPX) in the leaves of cucumber seedlings were significantly increased by foliar application of H₂O₂, but this did not occur in tomato leaves. Although one or two isoforms of SOD, HPX, and PPO isozymes in tomato leaves were suppressed by foliar application of H₂O₂, the total gel activities of the antioxidant enzymes were increased. These results suggest that foliar application of H₂O₂ before a crop is subjected to heat stress may be an effective and method to alleviate heat stress.

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Plants of Gypsophila paniculata L. ‘Bristol Fairy’ were grown in boxes at nine different shoot densities to know how the number of florets per shoot, a basis of flower quality, was determined during plant growth and development. Four components were defined to analyze the number of florets per shoot (FN): number of nodes (NN), primary branches (PB), secondary branches (SB), and units (= dichasia: UN). NN, PB, SB, UN, and FN were considered to be determined in this order during plant growth and development. Fresh weight, stem diameter (SD), PB, SB, UN, and FN of cut flowers decreased as shoot density increased. Total weight of cut flowers and total number of florets per box were almost equal, except in three low-density plots. Days to visible bud and days to flowering tended to decrease as the number of shoots per plant decreased. Path analysis was used to estimate the interrelationship among components. Stem diameter was defined as an outer variable. Path coefficients of stem diameter for NN, PB, SB, UN, and FN were −0.520, 0.686, 0.725, 0.589, and 0.408, respectively. Path analysis indicated that stem diameter had strong direct effects on each component. The correlation coefficient between SD and FN was 0.985. Stem diameter has a strong indirect influence on the number of florets per shoot and can be used as an index to predict FN.

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We estimated the ploidy level of 45 pot carnation cultivars by means of flow cytometry (FCM). The results strongly suggested that 27 cultivars are diploid, 3 are triploid, and 15 are tetraploid. To verify the actual ploidy levels, we counted chromosome numbers in the root tips of one cultivar at each ploidy level. This revealed that ‘Camille’ was diploid, ‘Baby Heart’ was triploid, and ‘Tula’ was tetraploid. Our results suggested that the ploidy level varies among pot carnation cultivars. We analyzed the genotypes of 32 cultivars by using five simple sequence repeat (SSR) markers to estimate the correspondence with FCM ploidy levels and to analyze genetic diversity. Ploidy estimated from the maximum number of alleles per locus corresponded with that estimated by FCM among diploid and triploid cultivars, but not among tetraploids. Among diploid pot cultivars, we found only three or four alleles per locus, and most alleles were common to diploid cut cultivars. On the other hand, triploid and tetraploid pot cultivars had four to eight alleles per locus, and most were unique to given ploidy levels. SSR analysis suggested that diploid pot cultivars were derived from cut cultivars, while triploids and tetraploids were produced by crossing wild Dianthus spp. and similar genetic resources. In total, 30 pot cultivars with different ploidy levels could be successfully identified from the genotype of five SSR markers.

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A system dynamic model of dry matter distribution between each inflorescence was constructed for sweet pea plants during flowering. The amount of dry matter distributed to each inflorescence is proportional to the product of dry matter and the relative growth rate of the inflorescence in the model. When the total dry matter supplied to the inflorescence per day is changed, the change of dry matter of the inflorescence is continuous without converging. Conversely, when the total dry matter supplied to the inflorescence per day is kept constant, the change in dry matter of the inflorescence converges immediately. From these simulation results, the hypothesis was formulated that the change in dry matter of an inflorescence is suppressed by reducing the change in total dry matter supplied to the inflorescence. Next, bud abscission and fluctuation in the number of buds per inflorescence under overnight supplemental lighting conditions on cloudy or rainy days was investigated. Overnight supplemental lighting of photosynthetic photon flux density 80 μmol·m⁻²·s⁻¹ enhanced dry mass production. This hypothesis was not supported because supplemental lighting treatment had no effect in suppressing fluctuation in the number of buds per inflorescence; however, supplemental lighting treatment was effective in preventing bud abscission and suppressing fluctuation in the number of buds per cut flower.

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Chrysanthemum stunt viroid (CSVd) is one of the problematic pathogens known to infect chrysanthemum (Dendranthema grandiflorum) plants and causes various symptoms, such as a reduction in plant height, which is a serious problem in cut flower production. No natural sources with resistance to CSVd have been reported. By quantifying the CSVd titer within the plant, we identified the cultivar ‘Utage’ as a plant in which the increase of the CSVd titer was slowest among 6 cultivars tested. ‘Utage’ self-pollinated, and 67 resulting seedlings were screened for CSVd resistance using reverse transcription polymerase chain reaction (RT-PCR), nested-PCR, micro-tissue (MT) direct RT-PCR, and real-time RT-PCR. Of these 67 seedlings, 9 plants lacked the obvious CSVd band detected by RT-PCR. Five months after grafting to CSVd-infected plants, the CSVd titers of 3 plants (C7, A30, and A27) were about 1/240, 1/41000, and 1/125000 compared to that of ‘Utage’, respectively. These 3 plants were comfirmed to have strong resistance to CSVd. In C7, local distribution of CSVd was observed in the youngest expanded leaf by micro-tissue direct RT-PCR and in situ hybridization. For A30 and A27, CSVd was hardly detected in the whole plant. These 3 plants will contribute to the elucidation of CSVd resistance mechanisms.

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There have been few reports on the morphology of flower opening, despite its horticultural significance. It is not clear when cell division stops during rose petal development or what changes occur in cell morphology. This study aims to clarify the details of cell morphological changes during rose petal development. Rose (Rosa hybrida L. ‘Sonia’) petals were sampled in six flower bud stages. Cell morphological changes were observed by light microscopy, transmission and scanning electron microscopy using cross sections of the petals, and the number of epidermal cells was measured using Nomarski differential interference contrast microscopy. The number of epidermal cells increased with flower opening, but the rate of increase in the number of abaxial epidermal cells slowed down at an earlier stage than in adaxial epidermal cells. The increase in the epidermal cell area was much more rapid in later stages compared with the increase in cell number, suggesting that petal growth in later stages is mainly due to cell expansion. During flower opening, the unique expansion of spongy parenchyma cells produced large air spaces. Epidermal cells of the upper part showed obvious lateral expansion. In particular, marked expansion of adaxial epidermal cells with enlargement of the central vacuole was observed. Differences in the patterns of cell expansion among cell types and locations would contribute to the reflex of petals during rose flower opening.

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In order to prevent delayed flowering of Chrysanthemum morifolium ‘Jinba’ during winter and spring cut-flower production, the effects of exposing rooted cuttings to long days (the vegetative growth stage), or mother plants to temperature, on the growth and flowering of plants were investigated. Days to flower budding in plants in short days, propagated from mother plants exposed to ambient low temperature, grown at a constant temperature regime of 20°C or 25°C in long days, were reduced compared with those of plants grown at 10°C or 15°C. Flower budding in rooted cuttings grown at 10°C in long days was delayed compared with 20°C or 25°C treatments when the rooted cuttings were subsequently grown at the same temperature in short days. The increase in leaf number in short days was also reduced with 20°C or 25°C treatment compared with 10°C treatment. In response to treatment with a constant temperature regime of 20/15°C or 20/20°C in long days for 2–8 weeks, days to flower budding in short days was significantly reduced in response to 20/20°C for 4, 6, or 8 weeks than the other treatments; differences among these treatments were not significant. Flower budding of rooted cuttings propagated from mother plants grown at a minimum temperature of 15°C was advanced compared with from mother plants exposed to ambient low temperature. These experiments show that to avoid delayed flowering of ‘Jinba’ for winter and spring production, rooted cuttings, propagated from mother plants exposed to ambient low temperature, must grow at a minimum temperature of 20°C for at least 4 weeks, or rooted cuttings should be taken from mother plants grown at a minimum temperature of 15°C.

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The structure of leaves and flowers of wild-type and pleiotropic maple-willow (m^w) mutant strain of Japanese morning glory (Ipomoea nil) was studied. The results provide a standard description for the morphology of I. nil and the morphological effects of this m^w mutant on all lateral organs. We found that the m^w mutation decreases the lamina width of all lateral organs by reducing cells in the transverse direction. We also established that the m^w mutation transforms the tri-lobed leaf into a slender willow-like leaf. It also results in the absence of the short tube in the calyx, changes the funnel-shaped sympetalous corolla to almost apopetalous, and modifies the normally syncarpous gynoecium to nearly apocarpous. The m^w mutation may cause a pleiotropic morphological phenotype of leaf and floral organs by reducing their lateral growth and fusing regions in the calyx, corolla, and gynoecium; however, the lower corolla tube and the septa and placentas of the lower portion of the ovary are as in the wild-type. Therefore, we suggest that in the mature leaf and floral organ structures, the homologous portions that may be formed by the same developmental processes are morphologically distinct. The MAPLE gene may be involved in lamina width growth and organ fusion in all lateral organs.

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