Horticulture Journal最新文献

Gladiolus (Gladiolus spp.) florets exhibit low ethylene sensitivity. Accordingly, the wilting of their tepals is an ethylene-independent process. Both trehalose and cycloheximide can extend the vase life of gladiolus florets. Floral senescence is probably regulated by programmed cell death. However, senescence-related genes have not been thoroughly investigated, except in ethylene-sensitive species. In this study, we analyzed the expression of senescence-associated genes by conducting transcriptome (RNA-seq) analysis. First, we examined the effects of 0.1 M trehalose (Tre), 300 μM cycloheximide (CHI), and 50 μM chloramphenicol (CAP) treatments on postharvest quality and senescence-related gene expression in gladiolus ‘Fujinoyuki’ cut florets. The Tre and CHI treatments extended the vase life of gladiolus florets by about 1 day, i.e., 30% of Cont. Tepals were sampled at 0 days (0d) and 2 days (2d) post-treatment. The RNA-seq analysis of floret tissues generated 81,136 unique sequences. Moreover, 2,892, 4,670, and 57 differentially expressed genes were identified from the 0d_Control (Cont) vs 2d_Cont, 2d_Cont vs 2d_CHI, and 2d_Cont vs 2d_Tre comparisons, respectively. Gene Ontology (GO) analysis suggested that cysteine-type endopeptidase activity was significantly higher for 2d_Cont than for 0d. Additionally, the 0d vs 2d_Cont comparison showed the cell wall-related GO terms were more enriched for 2d_Cont. The Kyoto Encyclopedia of Genes and Genomes analysis revealed an increase in the expression of sucrose synthesis-related genes in the 2d_Cont samples. Among the genes involved in starch and sucrose metabolism, the genes mediating cell wall degradation were more actively expressed in the 2d_Cont samples than in the 2d_CHI samples. The fragments per kilobase per million reads (FPKM) values were used to select candidate senescence-related gene families, including the cysteine protease, invertase, peroxidase, pectinesterase, and transcription factor (NAC [no apical meristem (NAM), Arabidopsis transcription activation factor (ATAF), and cup-shaped cotyledon (CUC)] and WRKY) families. The expression levels of transcription factor genes, including NAC 048, 68, 073 and WRKY 6, 11, 24, were validated by qPCR. The expression of these NAC and WRKY transcription factor genes was upregulated by CHI, suggesting their involvement in senescence or side reactions in gladiolus tepals. This study revealed several candidate genes and associated GO terms for senescence of cut florets, but further study is needed, especially on key genes, including transcription factors.

The Tall Spindle apple (Malus × domestica Borkh.) planting system achieves high early and sustained yields and excellent fruit quality. This system requires high-density planting (1,000–1,500 trees/acre) of highly branched (feathered) nursery trees, which increases the total cost of nursery trees purchased. To supply large quantities of highly feathered nursery trees at low prices, the nursery cycle should be shortened to one year. However, it is difficult to naturally obtain one-year-old nursery trees with sufficient feather number and length. Repeated spraying with 6-benzyladenine (BA) has been used as a conventional method to induce feather formation in apple nursery trees. We recently demonstrated that gibberellin A₃ (GA₃) treatment also increases the feather number on young apple trees. Here, we investigated the effects of GA₃ (0, 100, 500, and 1,000 μM) and BA (0, 75, 150, and 300 mg·L⁻¹) combinations on the production of well-feathered trees over a one-year cycle. Among the 16 GA₃ and BA combinations, repeated (7 or 9 times) spraying with 1,000 μM GA₃ + 300 mg·L⁻¹ BA solution (3 or 5 mL) was the most effective method for producing highly feathered nursery trees of ‘Fuji’/JM7 over a one-year cycle. In two trials, trees treated with 1,000 μM GA₃ + 300 mg·L⁻¹ BA had 0.9–1.0-fold greater terminal shoot lengths, 1.5–1.9-fold greater feather numbers (≥ 1 cm), 2.0-fold greater feather numbers (≥ 5–< 50 cm), 1.1–1.2-fold greater feather lengths, and 0.9-fold greater trunk diameters than those treated with 300 mg·L⁻¹ BA (conventional method). The feathers of trees treated with 1,000 μM GA₃ + 300 mg·L⁻¹ BA were predominantly 1–30 cm long (≥ 94.5%), and only few large feathers were observed. Thus, compared with the conventional method, treatment with 1,000 μM GA₃ + 300 mg·L⁻¹ BA facilitated the production of highly feathered nursery trees over a one-year cycle. It also reduced the time and labor cost required to obtain a large number of well-branched nursery trees needed for high-density plantings such as in the Tall Spindle system.

Passion fruit has edible arils with a complicated structure. Each aril has three different membranes; an external membrane, an internal membrane with a fimbriate structure at the basal area, and a transparent membrane that completely envelops the seed. It was reported that juice quality, including organic acid and sugar contents, varied depending on the extraction method. So, organic acid and sugar are potentially localized inside the aril. In this study, using three cultivars (purple passion fruit, yellow passion fruit, and ‘Summer Queen’, a hybrid variety between the two), juice qualities of different aril parts were determined. The aril was separated into three parts, that is, the outer pulp (OP), the distal part of the inner pulp (DIP), and the basal part of the inner pulp (BIP). The OP included the external membrane and the juice held by this membrane. The DIP surrounding the seed and the BIP was a fimbriate structure attached to the internal membrane. In all varieties, titratable acidity (TA) and citric acid content at DIP were higher than those at OP and BIP, although there were some differences among the varieties. Malic acid content did not vary among the parts. Total soluble solid content (TSS) at BIP was the highest among the parts, and glucose, sucrose, and fructose contents at DIP were lower than those at BIP. Purple passion fruit had a high juice content at OP and the yellow cultivar had high juice content at DIP, while the hybrid between the two showed intermediate characteristics. Organic acid and sugar were localized inside the aril in the passion fruit cultivars; the citric acid content and TA at DIP were higher than those at OP and BIP, and TSS at BIP was higher than those at DIP and OP. Therefore, adjusting the juice extraction intensity may be needed depending on the required juice quality.