Since both artificial pollination and fruit thinning are necessary for marketable fruit production of Japanese pears (Pyrus pyrifolia (burm. f.) Nakai) in Japan, about a 20% fruit set is ideal without pollination because only 5% of flowers are actually subjected to fruit production. In this study, copper (Cu2+) and ferrous (Fe2+) ions were shown to be effective for inducing a nearly-ideal fruit set of the Japanese pear ‘Kosui’. Fruit induced by ferrous sulfate (FeSO4) solution or a Bordeaux mixture, which is a combination of copper sulfate (CuSO4), lime, and water, were parthenocarpic, because 1) self-pollen tube growth was not promoted by Cu2+ and Fe2+, 2) almost no perfect seeds were observed at harvest, and 3) Cu2+ and Fe2+ acted as strong inhibitors of pollen tube growth in vitro. The effective stage for inducing parthenocarpy was sprouting time to 4 days after anthesis in the Bordeaux mixture, and sprouting time to 4 days before anthesis in the FeSO4 solution. Annual changes in the effectiveness were found in both chemicals, and the Bordeaux mixture showed no inhibitory effect on the fruit set of cross-pollinated flowers. The growth of Bordeaux mixture-induced fruit was improved by gibberellin (GA) paste or GA paste mixed with N-(N-(2-chloro-4-pyridy1)-N'-phenylurea (CPPU) treatment of the fruit stalk; the treated fruit was about 100 g heavier than the untreated fruit. The GA paste treatment is currently conducted to promote fruit growth and maturation in ‘Kosui’ fruit production in Japan, and the Bordeaux mixture can be substituted for chemical fungicide generally used before anthesis to control scab and black spot disease. Accordingly, the Bordeaux mixture is a promising chemical for great labor-saving in ‘Kosui’ cultivation.
In order to promote increases in the size of ‘Kosui’ Japanese pear [Pyrus pyrifolia (Burm.) Nakai] fruit by plant growth regulators, we applied gibberellin (GA)3+4 paste [2.7% (w/w), A3:A4 = 90:10] in combination with prohexadione-calcium [1%, PCa; BAS-125 (3-oxido-4-propionyl-5-oxo-3-cyclohexene-carboxylate)], an inhibitor of GA 2β-hydroxylation that catabolizes active GA into an inactive form, to fruit pedicels at approximately 30 days after full bloom. GA3+4+PCa treatment advanced fruit growth only in the early stages, but fruit weight did not show any significant differences between the untreated control and GA3+4+PCa-treated fruits at harvest. In contrast, when GA4+7 [2.7% (w/w), A4:A7 = 66:34] was applied, the fruit weight at harvest was greater than that of untreated fruit. Moreover, GA4+7 treatment in combination with PCa resulted in an even higher fruit weight at harvest. The GA4 concentration in fruit flesh was not affected by GA3+4 application at 1 week after the treatment (WAT) either with or without PCa, but GA4 levels increased with GA4+7+PCa treatment, resulting in a significant increase in fruit weight at harvest. A single GA4+7 application almost doubled the GA4 concentration compared with the untreated control, but the difference was not significant. These results indicate that fruit weight at harvest was greater when the GA4 concentration was higher in the fruit flesh at 1 WAT. The higher concentration of GA4 in the GA4+7+PCa-treated fruit compared with the GA4+7 treatment alone may be attributed to the function of PCa that acts to prevent the inactivation of GA4 to GA34 by inhibiting 2β-hydroxylation.
‘Hasshu’, a dwarf budsport that originated from the leading persimmon cultivar ‘Hiratanenashi’ (Diospyros kaki Thunb.), was discovered in Japan in 2005. Although ‘Hiratanenashi’ is seedless because of anisoploidy (2n = 135 = 9x), ‘Hasshu’ produces some small normal seeds. In this study, we investigated differences in the morphological characteristics of the vegetative organs and fruits and in the ploidy level between ‘Hasshu’ and ‘Hiratanenashi’. The shoot length, internode length, and leaf size of ‘Hasshu’ were smaller than those of ‘Hiratanenashi’. ‘Hasshu’ bore smaller flowers than those of ‘Hiratanenashi’ in late May, and had consistently smaller fruit than ‘Hiratanenashi’ at all fruit development stages. ‘Hasshu’ ripened in late October, similar to ‘Hiratanenashi’. Both ‘Hiratanenashi’ and ‘Hasshu’ are pollination-variant astringent (PVA) cultivars. Except for the deletion of one allele at ssrdk10, no differences were detected between the two cultivars at four simple sequence repeat (SSR) marker loci. By flow cytometric analysis and chromosome observation, we confirmed that ‘Hasshu’ was octoploid (2n = 120 = 8x), indicating that it was both a dwarf and a ploidy-reduction mutation. These results suggest that recovery of the ability to produce some normal seeds by ‘Hasshu’ may have been caused by the change in ploidy from anisoploid to isoploid.
Utilization of cover crops helps the establishment of environmentally friendly agriculture due to their nutrition supplying ability mainly in the current year of application, but cover crop-derived N also remains until the following year. In the present study, the nutritional effect of a cover crop on tomato production in a greenhouse in the following year was investigated using the 15N-labeling method. Hairy vetch (Vicia villosa R., HV) was used as a cover crop. 15N-labeled HV (1319 mg N/pot) was applied to a 1/2000 a Wagner pot, and a fresh market tomato (Solanum lycopersicum L.), ‘House Momotaro’ was cultivated in it at 0, 80, and 240 kg·ha−1 of N application in 2011 (N0HV, N80HV, and N240HV). After the tomato cultivation in 2011, the soil was stored in a greenhouse (the temperature varied from −4.1°C to 26.5°C) without any water or fertilizer. Tomatoes were cultivated again in the Wagner pots containing the soil used in 2011, to which was added the same rate of N fertilizer (0, 80, and 240 kg·ha−1 of N) and unlabeled HV (935 mg N/pot) in 2012. Total N uptake of tomato plants was higher in N240HV (2377 mg/plant), followed by N80HV (1760 mg/plant), N0HV (1498 mg/plant). On the other hand, the uptake of N derived from HV applied in 2011 (HV2011, 1319 mg N/pot) was not different among the treatments (57.7 mg/plant on average); thus, nitrogen use efficiency derived from HV2011 in 2012 was 4.4% on average. This value was much lower than that in 2011 (47.1% on average), but HV2011-N also remained in the soil after the tomato cultivation in 2012 (500 mg N/pot). The distribution ratios of HV2011-N to the fruit in 1st and 2nd fruit clusters that developed in the early growth period were higher than those of N derived from soil, fertilizer, and HV applied in 2012. These results showed that although the N supplying effect of HV was small, HV could be available not only as short-term N source, but also long-term N source, and HV-derived N applied in the previous year was absorbed by tomato plants during a relatively early growth period in the following year.
Lilium leichtlinii (2n = 2x = 24) is the most commercially cultivated edible lily in Japan, although viral and fungal diseases are severe problems. Triploid L. lancifolium (2n = 3x = 36), the bulbs of which are also edible, adapts well to the climate in Japan, and feral triploid L. lancifolium plants are often seen along roadsides and in croplands. Thus, triploid L. lancifolium is an important genetic resource for edible lilies, but it develops many bulbils (aerial bulbs) on leaf axils. Bulbil formation is undesirable for edible lilies because bulbils can compete for photosynthate with bulbs, which limits the use of triploid L. lancifolium in commercial production. Edible lily cultivars have been bred by intraspecific crosses within L. leichtlinii, although interspecific hybridization, which increases the level of genetic variation, is the major technique used to breed floricultural lily cultivars. In this study, interspecific-hybrid plants were developed by crossing triploid L. lancifolium and L. leichtlinii, and their characteristics, including bulbil formation ability, were evaluated. The crosses of triploid L. lancifolium × L. leichtlinii developed aneuploid plants, of which the chromosome number ranged from 26 to 34. Bulbil formation ability was continuously distributed in the F1 offspring, although 86% of F1 plants did not develop bulbils, indicating that many aneuploid plants without bulbils are developed by this cross combination. The plants harboring abnormal anthers were segregated in the hybrids. In addition, pollen germination in the F1 hybrids was lower than 20%, and 85% of the hybrids exhibited no pollen germination. However, abnormal anther morphology and low pollen fertility should not be major problems for edible lily production because bulbs are the main commercial output. These results indicate that interspecific hybridization between triploid L. lancifolium and L. leichtlinii has the potential to develop elite edible lily cultivars.
Rhododendron simsii Planch. is distributed in eastern Asia, such as Ryukyu Islands of Japan, southern China, Taiwan, and Vietnam. It is a semideciduous shrub with five-lobed red corollas and reddish-purple blotches on the upper petals. From microscopic observation, reddish-purple colored cells were distributed only in the adaxial subepidermis of blotch areas in the upper petals, while red colored cells were observed in the whole epidermis of both upper and lower petals. Even though the anthocyanin constitutions of upper and lower petals were the same, the λmax of absorbance of fresh upper petals was 514.9 nm, while it was 505.7 nm in the lower petals. In R. simsii flowers, cyanidin glycosides were major anthocyanins in whole petals. Quercetin glycosides were detected in reddish-purple blotch areas, but they were found only in trace amounts in lower petals. Anthocyanins and flavonols were extracted, and separated by column chromatography. Bathochromic shift (9.7 nm) was observed in mixed solution of anthocyanin and flavonol at a ratio of concentration of 1:7.5. These results were similar to the bathochromic shift obtained between upper and lower petals of intact flowers (9.2 nm). From these findings, co-pigmentation between anthocyanin and flavonol (quercetin glycosides) seems to be a key factor of reddish-purple color of the blotch area in the upper petals of R. simsii flowers.
Petal growth associated with flower opening is due to cell expansion. To elucidate the role of soluble carbohydrates in expansion of petal cells in Eustoma grandiflorum, its soluble carbohydrates were identified, and changes in their subcellular concentrations during flower opening were investigated. In addition to glucose, fructose, sucrose, and myo-inositol, d-bornesitol was identified using 1H-NMR. d-Bornesitol was the major soluble carbohydrate in leaves and stems. Given that cyclitols are known to be the translocated carbohydrates in alfalfa, phloem exudate was analyzed. However, the translocated carbohydrate was suggested to be sucrose, and not d-bornesitol. In the petals, glucose and sucrose content increased whereas d-bornesitol and myo-inositol contents were almost constant during flower opening. The fructose content in petals was very low. Glucose, sucrose, myo-inositol, and d-bornesitol were found mainly in the vacuole, although sucrose was also found in the cytoplasm. In the petals of open flowers, glucose and sucrose concentrations in the vacuole increased to 60 and 53 mM. Inorganic ion concentrations in the symplast and apoplast did not increase during flower opening. The osmotic potential of the symplast and apoplast in the petals was lower at the open stage than the potential of those at the bud stage, and this difference was mainly attributed to increases in glucose and sucrose concentrations. The results suggest that the accumulation of glucose and sucrose in the vacuole reduces the symplastic osmotic potential, which appears to be involved in the cell expansion associated with flower opening, but that the contribution of d-bornesitol as an osmoticum to cell expansion is limited in Eustoma.
The aims of this study were to examine the effects of different temperatures on seed germination and initial long-day (LD) or short-day (SD) duration on growth, floral initiation, and development of Hosta yingeri S.B.Jones. The germination percentage of H. yingeri seeds was > 90% at 5°C and between 15°C–30°C. The lowest time to the first germination (TFG) and the mean germination time (MGT) were observed at around 30°C. The optimum temperature for germination can be around 30°C considering the final germination percentage, TFG, and MGT together. Plant height, number of leaves, and leaf length increased as the initial SD duration decreased. The percentages of plant bearing buds were 50%, 50%, 20%, 10%, and 0% when the initial SD treatments were 0, 3, 6, 9, and 12 weeks with 29, 26, 23, 20, and 17 weeks of LDs, respectively. No plants flowered when they were exposed to the initial LD conditions. Flower spike length, number of visible buds, and number of open flowers increased as the duration of the initial SD decreased. Four-week-old H. yingeri required ≥ 26 weeks of LD duration to achieve > 50% flowering.
We investigated differences in flower longevity, ethylene production, and ethylene sensitivity among pot carnation cultivars by quantitative PCR analysis. The flower life of ‘Polaris’ was significantly longer than that of ‘Ariel’ (control cultivar), ‘Orange Duo’, and ‘Lemon Soft’. The flowers of ‘Polaris’ produced little ethylene, and had low expression of the ethylene biosynthesis genes DcACS1 and DcACO1. The transcript levels of senescence-related (SR) genes DcCP1, DcbGal, and DcGST1 increased in petals of ‘Ariel’, ‘Orange Duo’, and ‘Lemon Soft’ at senescence, but were very low in ‘Polaris’. These results suggest that the low ethylene production in ‘Polaris’ is caused by low expression of DcACS1 and DcACO1, as in long-life flowers of the cut carnation cultivars ‘Miracle Rouge’ and ‘Miracle Symphony’. The ethylene sensitivity of ‘Orange Duo’ and ‘Lemon Soft’ was lower than that of both ‘Ariel’ and ‘Polaris’. Petals of ‘Orange Duo’ and ‘Lemon Soft’ wilted, and inrolled more slowly than those of ‘Ariel’ and ‘Polaris’, despite the upregulation of ethylene biosynthesis genes (DcACS1 and DcACO1), DcCP1, DcbGal, DcGST1, and DcEIL3 in petals of all cultivars upon application of exogenous ethylene. These results imply that only the components related to the inrolling of petals are altered in these ethylene-insensitive cultivars.
Summer-to-autumn-flowering small-flowered spray-type (SAFS) chrysanthemums (Chrysanthemum morifolium Ramat.) are commercially important in Japan, and there is an occasional increased demand for these flowers. However, under current cultivation methods, the quality of spray formations is compromised in order to maintain a sufficient production rate at times of peak demand. This study investigated the effect of interrupted lighting (IL), the intercalation of a period of long days (by night interruption) into the natural day length (NDL) period of growing, in order to regulate spray formations in SAFS chrysanthemum cultivars ‘Haruka’ and ‘Subaru’, in which lighting can markedly delay flowering. The effects of the NDL period before IL and those of the IL period were investigated. First, we investigated the effect of 2–12 days of NDL followed by 12 days of IL. Plants subjected to 2–6 days of NDL had longer flower clusters and a greater number of flower buds on the upper lateral flower stems and developed a broom-like spray. Next, we investigated the effect of 4–20 days of IL after 4 days of NDL. Plants subjected to 8–20 days of IL had longer flower clusters, more flower buds on the upper lateral flower stems, and broom-like sprays. These changes were more pronounced when the IL periods were prolonged. Our results showed that spray formation in SAFS chrysanthemum cultivars ‘Haruka’ and ‘Subaru’ can be regulated by controlling the timing and period of IL.
A double-flowered torenia (Torenia fournieri Lind. ex Fourn.) mutant, “Petaloid”, was obtained from selfed progeny of the “Flecked” mutant, in which the transposition of the DNA transposon Ttf1 is active. A normal torenia flower has a synsepalous calyx consisting of 5 sepals, a synpetalous corolla consisting of 5 petals, 4 distinct stamens, and a syncarpous pistil consisting of 2 carpels. In contrast, a flower of the “Petaloid” mutant has 4 distinct petals converted from stamens, whereas the calyx, corolla, and pistil remain unchanged. The double-flower trait of the “Petaloid” mutant was unstable; some or all of the 4 petals converted from stamens frequently reverted to stamens. Furthermore, most S1 plants obtained from self-pollination of the somatic revertant flower bore only normal single flowers. In petals converted from stamens, expression of the C-class floral homeotic gene T. fournieri FARINELLI (TfFAR) was almost completely inhibited. This inhibition was caused by insertion of Ttf1 into the 2nd intron of TfFAR, whereas reversion of converted petals to stamens was caused by excision of Ttf1 from TfFAR. The clear correspondence of the TfFAR genotype to the floral phenotype suggested that homozygous TfFAR alleles with the Ttf1 insertion caused the mutant phenotype. In contrast, TfFAR was moderately expressed in the pistil of the “Petaloid” mutant, leaving the pistil unchanged. We succeeded in inactivating Ttf1 transposition by cross-pollination between mutant and normal-type plants to genetically separate the transposon Ttf1 from the unidentified factor activating its transposition, which made the “Petaloid” mutation more stable.