Horticulture Journal最新文献

Malformed flowers similar to super-double-flowers were observed in potted ‘Cherie’ carnation (Dianthus caryophyllus L.) plants. In the malformed flower (mlf) lines, most flowers were malformed at 15°C, but not at 20°C. Thus, we hypothesized that the malformation was due to a mutation associated with morphological responses to temperature. In this study, RNA-sequencing analysis of young flower buds and whole-genome re-sequencing of leaves were performed using wild-type (WT) and mlf plants to identify malformation-related candidate genes. The RNA-sequencing analysis revealed 691 significant differentially expressed genes (DEGs) between WT flower buds at 15 or 20°C and mlf flower buds at 15°C. The Gene Ontology (GO) analysis indicated that metal ion binding, transmembrane transport, and anaphase-promoting complex enriched GO terms in mlf, whereas translation and ribosome enriched GO in terms of WT. The Kyoto Encyclopedia of Genes and Genomes analysis revealed an increase in the expression of 9-cis-epoxycarotenoid dioxygenase (NCED), Pyrabactin Resistance 1-Like (PYL), and Calmodulin (CAM), but a decrease in the expression of Histone H4, in mlf. The fragments per kilobase per million reads (FPKM) values were used to select candidate malformation-related DEGs. Transcription factor genes, including WUSCHEL (WUS) and STERILE APETALA, were upregulated in mlf, whereas PISTILLATA-like protein, MADS-box protein CMB2, and F-box UNUSUAL FLORAL ORGANS were downregulated. Heat Shock Cognate 70 kDa (HSC70) and Temperature-induced lipocalin-1 were upregulated in mlf, but genes encoding histones and ribosomal proteins were downregulated. Moreover, NCED1, PYL8 and 9, and cytokinin-related genes were upregulated in mlf. Using whole-genome re-sequencing data, sequence variants were detected in the upstream regions and exons of WUS, HSC70-1 and 2, CAM7, and ribosomal protein-encoding genes. Furthermore, examination of the F₁ progeny derived from WT and mlf crosses with cultivars producing fertile pollen revealed a significant difference in the proportion of malformed flower phenotypes between WT and mlf regardless of temperature, suggesting that the malformed flower phenotypes of mlf can be inherited. Candidate genes associated with the temperature-dependent super-double-flower phenotypes were examined.

To develop novel humidification technology for strawberry production to achieve higher yields and improve fruit quality, four Japanese June-bearing strawberry cultivars were grown in a greenhouse with or without humidification treatment (HT) based on vapor pressure deficit (VPD). HT reduced VPD from transplanting to March, but did not affect the VPD condition from April to May. Soon after transplanting, HT enhanced plant growth and the daily leaf-emergence rate, and significantly advanced flower-bud emergence and first-fruit harvest for the first inflorescence for ‘Koiminori’, ‘Kaorino’, and ‘Saga i9’. However, HT significantly delayed flower-bud differentiation and first-fruit harvest of the second inflorescence of ‘Kaorino’ and ‘Yumenoka’. HT significantly increased the total weight of marketable fruit for ‘Koiminori’, ‘Kaorino’, and ‘Saga i9’. In addition, HT significantly increased the total fresh weight of marketable fruit harvested until December for ‘Koiminori’ and ‘Saga i9’. HT did not significantly affect the firmness of fruit skin (FFS), soluble-solid content (SSC), fruit acidity (FA), or SSC/acidity of ‘Koiminori’, ‘Kaorino’, and ‘Yumenoka’.

Anthocyanins are ubiquitously accumulated in diverse plant species and play crucial roles in plant development. In addition, anthocyanin pigmentation is associated with significant characteristics in the flowers and fruits of horticultural products. Notably, anthocyanin biosynthesis and storage are known to be affected by environmental factors. High ambient temperatures often suppress anthocyanin accumulation in flowers and fruits, raising concerns regarding the increase in atmospheric temperatures caused by global warming. Therefore, a comprehensive understanding of the mechanisms underlying the effects of high ambient temperatures on the regulation of anthocyanin biosynthesis and storage is necessary to maintain pigment quality and quantity of the products. In this review, we provide comprehensive information on the role of high-temperature-related signaling pathways in the regulation of anthocyanin biosynthesis. The expression of genes involved in anthocyanin biosynthesis is mainly regulated by R2R3-MYB activators, R2R3-MYB repressors, and R3-MYB negative regulators. The expression levels of R2R3-MYB activators decrease under high-temperature conditions, as observed in many flowers and fruits. The upregulation of R2R3-MYB repressors and R3-MYB negative regulators has also been demonstrated in some plant species under high-temperature conditions. The high-temperature-related signaling pathways have been evaluated mainly in the vegetative organs of Arabidopsis and apple fruits. In these organs, light strongly influences anthocyanin biosynthesis in addition to ambient temperatures. The CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1)-ELONGATED HYPOCOTYL 5 (HY5) module and B-box proteins upregulate the R2R3-MYB activators under light conditions, while they downregulate the R2R3-MYB activators under high-temperature conditions. However, the pathways that transduce high-temperature signals in flowers are poorly understood. Unlike in fruits and vegetative organs, light exerts relatively small effects on anthocyanin pigmentation in flowers, suggesting that the COP1-HY5 module-independent pathway could be responsible for the regulation of R2R3-MYB regulators in many flowers. Further research to clarify the related signaling pathways in flowers is needed to find solutions to overcome the problem of color fading caused by high ambient temperatures. In addition, exceptional cases have been reported in which high temperatures do not inhibit or enhance the anthocyanin pigmentation of flowers. Such species can prove helpful in elucidating the mechanisms underlying temperature-mediated regulation of anthocyanin pigmentation and as parental materials for crossbreeding.

Red-fleshed kiwifruit exhibits favorable nutritional characteristics and is renowned for its sweet flavor. However, the majority of red-fleshed kiwifruit species are diploids, producing diminutive fruit sizes and limited resistance to abiotic stress. To cultivate new cultivars with superior traits, we employed colchicine treatment to induce tetraploidy from the diploid Actinidia chinensis cv. ‘Donghong’. In this study, a 20% induction rate was achieved by immersing the apical meristem in 0.2% colchicine solution for 48 hours. The induced tetraploids demonstrated larger stomatal size, lower stomatal density, higher chlorophyll content, and a lower chlorophyll a/b ratio compared to diploids; however, no significant difference in photosynthetic conversion efficiency was observed. Furthermore, the tetraploid red-fleshed kiwifruit grafted on the same tree exhibited superior fruit shape, quality, and weight compared to their diploid parent ‘Donghong’. The vitamin C content in tetraploid fruits increased by 62.6% compared to that in diploids. Also, the tetraploid ‘Donghong’ showed delayed phenology compared to the diploid from leaf buds to fruit ripening. This research not only generated a novel germplasm of tetraploid kiwifruit for future breeding, but also contributes to understanding the mechanism of polyploidy-induced trait variation in kiwifruit.

In Japan, wild evergreen azalea species with high ornamental value, such as Rhododendron ripense, grow naturally, and numerous cultivars have been developed based on these species. In this study, we utilized microsatellite markers to examine the genetic relationships among wild evergreen azalea species in Japan, particularly focusing on R. ripense, as well as assessing the genetic diversity of R. ripense. STRUCTURE analysis revealed that when K = 2, R. ripense appeared to be distinct from other species. However, when K = 4, the R. ripense population exhibited two separate clusters. Further analysis at K = 10 revealed genetic diversity within the R. ripense population, which was divided into five clusters reflecting their respective geographic distributions. Analysis of cultivars related to R. ripense based on the results of wild species suggested that most of the Ryūkyū-tsutsuji (R. × mucronatum) cultivars originated from the Yamakuni River in the northern Kyushu region or the San’in region of R. ripense.

This study investigated how fruit morphology and development, especially ostiole openness of young fruit, affect the thrips (Thysanoptera) resistance of various fig (Ficus carica L.) cultivars. The rate of fruits with thrips (TFR) and the damage (DFR) varied among the 24 cultivars surveyed. TFR and DFR were highest in ‘Masui Dauphine’ (syn. ‘San Piero’), a popular cultivar in Japan, and moderate in ‘Brunswick’, ‘Archipel’, and ‘Saint Jean’, but relatively low to almost zero in many other cultivars. Cultivar differences in DFR were correlated with the difference in the rate of ostiole hole (a hole larger than 0.1 mm in diameter towards the internal pulp) presence. However, thrips were also detected from fruits in which no ostiole hole was observed throughout the growing stages, so they are likely to be able to pass through narrower gaps. Of two predicted morphologies determining ostiole openness, i.e., scale loosening around the ostiole surface and obstruction of the ostiole interior by flowers, only the former was correlated with DFR, so that scale loosening in longitudinal and radial directions relative to the ostiole was actually observed. A general linear model (GLM) for likelihood of thrips detection for individual fruits, with cultivar, scale looseness in longitudinal and radial directions, and interactions between both looseness as explanatory variables, had the best fit at 15 days after fruit set. The results showed that fig cultivars with less loosening of several surface scales at around 15 days after fruit set tended to be less susceptible to thrips invasion.

Columnar-shaped apple (Malus × domestica Borkh.) trees are of interest because of their profitable and labour-saving characteristics based on high-density planting and robotic technologies. Recent studies have shown that the Co gene, which is responsible for the columnar shape, and MdPG1, which contributes to fruit storability and flesh texture, are located on chromosome 10 of the apple genome. In silico analysis and genotypic characterisation of our columnar breeding materials revealed that the unfavourable haplotype carrying both Co and the MdPG1-3 allele that confers low storability was retained in almost all of our current and historical columnar materials because of the strong linkage between the two genes. To overcome this limitation, we conducted large-scale marker-assisted selection to obtain plants harbouring a favourable haplotype conferring a columnar tree with improved storability, and high-quality flesh resulting from recombination events between these genes during meiosis. Large-scale marker-assisted selection of approximately 15,000 seedlings composed of five crosses resulted in the identification of 80 individuals harbouring the targeted recombinant haplotype. These individuals are valuable for breeding columnar apple cultivars with superior fruit quality.

Unpleasant odors are crucial in terms of consumer acceptance. However, the volatile compounds responsible for the unpleasant rubbery odor in green papaya have not been thoroughly documented. Therefore, the primary objective of this study was to identify these key volatile compounds and examine how they are influenced by different papaya cultivars, harvest seasons, and fruit maturity stages. Using gas chromatography-olfactometry (GC-O), five odorants were identified as having a rubbery odor, with benzyl isothiocyanate and 2-cyclohexen-1-one showing a significant positive correlation with rubber-like odor scores (r > 0.8). In the ‘Khaek Nuan’ cultivar, known for its strong rubber odor, the intensity of the rubber odor and the concentrations of (E)-1,2-cyclohexanediol were higher in cool season fruits and at the immature stage. Conversely, the ‘Yellow Flesh’ cultivar, which has a mild rubber odor, exhibited no significant effect of season or maturity on the unpleasant rubber odor or the presence of benzyl isothiocyanate and (E)-1,2-cyclohexanediol. By specifically targeting these odorants, effective strategies can be developed to mitigate or minimize the unpleasant smell through approaches such as genetic modification, management practices, or postharvest interventions.

When cut gerbera flowers absorb water after dry transport, some cultivars often exhibit petal curling, a phenomenon known as “Ben-sori” in Japanese. This study showed that the occurrence rate differed among gerbera cultivars, with ‘Aloha’, ‘Prime Time’ and ‘Kimsey’ being categorized as sensitive cultivars, while ‘Pinta’ and ‘Vivid’ were insensitive. In ‘Aloha’, petal curling caused the abaxial length and adaxial width of epidermal cells to be significantly shorter than in normal petals. ‘Aloha’ flowers harvested at later developmental stages were less affected by petal curling compared with those harvested at earlier stages. The petal length and width increased sharply at stage 4 (anthesis), and the development ray florets finished at stage 6 (flowers with anthers visible in three outermost rings in disk florets). Therefore, cut gerbera flowers that still have petal elongation potential may exhibit increased occurrence of petal curling symptoms. Lower absorption temperatures accelerated petal curling, and the most severe symptoms were observed at 5°C. Interestingly, when cut flowers absorbed water at 15°C, no symptoms were detected. We propose two ways to prevent the occurrence of petal curling in cut gerbera flowers: first, harvest flowers of sensitive cultivars at later developmental stages when anthers are visible in the two or three outermost rings of disk florets and second, allow water absorption at around 15°C after dry transport. These prevention strategies can resolve issues associated with petal curling for both flower retailers and customers and will improve the quality of cut gerberas.

The goal of this study was to assess whether irradiated pollen technology could be used in tomato breeding research. The effects of irradiation on pollen viability, fruit set rate, and embryo formation were investigated. For this purpose, pollens were exposed to gamma rays of 0, 50, 100, 200, 300, and 400 Grays (Gy). The effect of irradiation on pollen viability and tube growth was found to be significant based on counting and measurements performed under in vitro conditions at 24, 48, 72, and 144 h after irradiation. Fruit set and embryo formation in seeds were evaluated 30 days after pollination with pollen irradiated at different doses. It was determined that increasing the irradiation dose resulted in reduced pollen viability and tube length. Endosperm formation was detected in all seeds after 50 Gy of irradiation. However, 50 Gy had no effect on gynogenesis stimulation. Therefore, 100, 200, and 300 Gy doses stimulated embryo formation without endosperm, while 400 Gy of irradiated pollen did not support fruit to set. These results indicate the importance of harvesting time to obtain viable embryos. It should be retracted to an earlier time since late harvest resulted in necrosis of globular embryos on the 30^th day after irradiation. Pollination with one-day-old irradiated pollen was more suitable for gynogenesis induction. The results showed that the irradiated pollen technique can be applied in tomato breeding studies, especially in terms of purifying the obtained breeding lines in a shorter time. In particular, determining the appropriate induction dose for gynogenesis depending on the genotype is important for stimulation efficiency.