Horticulture Journal最新文献

Sweetness is one of the most important drivers of consumer preference in apples (Malus × domestica Borkh.). The increase in sugar during the ripening period of fruit is mainly brought about by the hydrolysis of starch accumulated before the ripening period. However, sugars are also continuously translocated into the fruit during the ripening period, as seen in watercored fruits. The objective of this study was to estimate the contribution of translocated sugars that accumulated in the apoplast to the increase in soluble solids content (SSC) of fruit during ripening. The amount of apoplastic solution (AS) tended to be high in the fruit of trees on vigorous rootstocks, such as ‘JM2’ and ‘Marubakaido’. On the other hand, fruit with more AS had lower SSC. Therefore, although AS increased during ripening, the contribution of AS to the increase in SSC was small. After fruit matured and during storage, dehydration increased the SSC of the fruit. On the other hand, the SSC decreased simultaneously due to a reduction in organic acids and any soluble solids, which was expressed as a decrease in titratable acidity (TA). Under standard refrigerated conditions, the increase in SSC due to dehydration and the decrease in SSC due to respiration were likely to be quantitatively comparable. The contribution of translocated sugars to the increase in SSC during ripening was small, suggesting that managing trees and fruit to increase starch accumulation before fruit ripening is crucial for the production of fruits with high sugar content.

Flowers of the early Polyantha roses, ‘Pâquerette’, ‘Mignonette’ and ‘Anne-Marie de Montravel’, have an unusual odor not found in other roses. Their ancestor is Rosa multiflora, a wild species native to Japan. In particular, ‘Anne-Marie de Montravel’ has a citrus scent with an old wooden closet-like odor. Gas chromatography (GC)-mass spectrometry analysis of the scent components of these roses revealed the presence of several terpenoids, benzenoids, and hydrocarbons, as well as the fatty acid derivatives methyl (E, Z)-2,4-decadienoate (MDD) and methyl (E, E, Z)-2,4,6-decatrienoate (EEZ-MDT). GC-olfactometry analysis of scent components of ‘Anne-Marie de Montravel’, identified EEZ-MDT and its isomers as the source of the unpleasant odor. MDD and EEZ-MDT are known as stink bug pheromones, but they were first detected in the scent of plants. We also analyzed the floral scent of several roses related to R. multiflora, namely: two plants of R. multiflora, two Hybrid Multiflora roses (‘Crimson Rambler’ and ‘Rose-Marie Viaud’), eight Polyantha roses (‘Cécile Brunner’, ‘Clothilde Soupert’, ‘Gloire des Polyantha’, ‘Madame Norbert Levavasseur’, ‘Marie Daly’, ‘Marie Pavié’, R. multiflora ‘Nana’, ‘Yvan Misson’), and one Miniature rose (‘Gourmet Popcorn’). EEZ-MDT and/or its isomers were detected not only in ‘Marie Daly’, ‘Marie Pavié’, R. multiflora ‘Nana’, and ‘Gourmet Popcorn’, which had an old wooden closet-like odor, but also in R. multiflora, ‘Rose-Marie Viaud’ and ‘Yvan Misson’, which do not exhibit that unpleasant odor. To produce the unusual odor in the rose fragrance, the EEZ-MDT and its isomers content must be above a certain percentage of the scent components.

Alternaria blotch, a major apple (Malus × domestica Borkh.) fungal disease in Japan, is caused by the Alternaria alternata apple pathotype that produces a host-selective toxin called AM-toxin. Although control of Alternaria blotch currently relies on spring-to-summer fungicide use, there is a growing need for sustainable agriculture practices that reduce chemical inputs in orchards. Therefore, breeding cultivars for resistance to Alternaria blotch is of particular interest. Given that ‘Golden Delicious’ (GD) and several of its offspring cultivars are moderately susceptible to the disease, a genetic analysis of their susceptibility was performed. Quantitative trait locus (QTL) analysis of the ‘Fuji’ × ‘GD’ population identified a single QTL on chromosome 11 in ‘GD’, which explained 48.7% of the phenotypic variation. This QTL was located in the same region as the previously identified susceptibility gene Alt derived from ‘Starking Delicious’. Therefore, we named it QTL Alt2, a putative allele of Alt (later renamed Alt1). Interaction analysis revealed that Alt1 was dominant over Alt2. A DNA marker set that simultaneously detects Alt1 and Alt2 was developed for breeding use. This marker shed light on the inheritance of the Alt locus in modern Japanese cultivars and selections. Moreover, Alt2 was less common than Alt1 in heirloom cultivars. These findings offer new insights into apple breeding for Alternaria blotch resistance and the interaction mechanism between apple and host-selective toxin-producing A. alternata.

Lisianthus (Eustoma grandiflorum [Raf.] Shinners) is one of the world’s major cut flowers, characterized by its wide variety of flower colors, flower shapes, long stem, and long vase life. Lisianthus is said to be scentless, but there are cultivars that have a weak or faint scent. Cats exhibit a characteristic response to lisianthus flowers similar to their response to Actinidia polygama leaves, which have a very weak scent for humans. These observations suggested that the scent of lisianthus flowers may have a component that attracts cats. The volatile components of Eustoma ‘New Lination White’ flowers, which has a weakly sweet scent, and 12 lisianthus cultivars, which have a very faint scent, were analyzed. Thirty-six kinds of volatile components were detected in the flowers of ‘New Lination White’, including four iridoid compounds (nepetalactone, isodihydronepetalactone, iridomyrmecin, and isoiridomyrmecin) and actinidine, which have been recognized as attracting cats. The major volatile components are sesquiterpenes, and phenypropanoids such as eugenol were identified as components with a sweet scent. Iridoid compounds and actinidine were detected only in flowers, but not in leaves or stems. In addition, iridoid compounds were detected in all 12 cultivars analyzed. Lisianthus flowers were thought to be scentless but we identified many volatile components, including iridoid compounds and actinidine, that attracts cats. This research is the first report on the scent of lisianthus flowers.

“Twining” along other objects is an important morphogenetic survival response of vine plants. The twining response, induced by the stimulus of touching a supporting object, is a form of “thigmomorphogenesis”. Ethylene is thought to play an important role in thigmomorphogenesis in higher plants, so it is likely to be involved in vine twining. However, the relationship between ethylene and vine twining is not well understood. We used vine cuttings excised from morning glory (Ipomoea nil (L.) Roth ‘Violet’) plants in order to investigate the effect of an ethylene inhibitor on elongation and twining. The vine cuttings required gibberellin for elongation and twining. In the vine cuttings with elongation and twining induced by gibberellin treatment, treatment with 1-methylcyclopropene (1-MCP), an ethylene action inhibitor, significantly decreased the angle of rotation and the spiral pitch of the twining. These results suggest that ethylene may be involved in either sensing a pole via touch and the morphological changes during vine twining or both. We also selected one of the genes for 1-aminocyclopropane-1-carboxylic acid synthase (ACS), which is a key enzyme in the ethylene biosynthetic pathway, with higher expression in tissues on the side touching the pole in twining vines as one of the candidate genes thought to be involved in vine twining in morning glory.

In the most popular fragrant rose cultivar in Japan, ‘Yves Piaget’, the petal edges are frequently malformed, curving toward the adaxial side. These malformed petals prevent normal flowering and weaken the flower fragrance, which significantly decreases the quality of this cultivar and increases financial losses of cut flowers. We refer to such malformed flowers as ‘incurved flowers’. It has been reported that jasmonic acid (JA) affects petal growth. Therefore, we attempted to control the number of incurved flowers by applying exogenous JA, methyl jasmonate (MeJA), during flower development before harvest. Two types of spray treatment were applied to the flower buds before flower opening; (1) 100 μM MeJA or (2) deionized water as a control. The 100 μM MeJA spray treatment before harvest reduced the incurved flower rate, with fewer incurved petals, and resulted in a significantly larger maximum flower diameter and longer stamen length. In addition, the 100 μM MeJA spray treatment before harvest tended to increase the number of days from the commercial harvest stage to full bloom and also significantly increased the maximum flower diameter of fully-bloomed flowers. We also analyzed the endogenous phytohormone content in the petals of normal and incurved flowers at each flower developmental stage. The results showed that at the beginning of the flower opening stage the petals of incurved flowers had higher indoleacetic acid (IAA) content and lower JA/jasmonoyl isoleucine (JA-Ile) content than those of normal flowers. In particular, the JA and JA-Ile contents in incurved petals were approximately one quarter of those in normal flowers. These results suggest that IAA, JA, and JA-Ile may be involved in the development of incurved flowers.

Treatment with calcium chloride (CaCl₂) is known to suppress the occurrence of flower stem bending and extend the vase life of cut gerbera. To clarify whether vase life extension by CaCl₂ is improved by combined treatment with gibberellin A₃ (GA₃), the effect of treatment with 50 mg·L⁻¹ GA₃, 5 g·L⁻¹ CaCl₂ or in combination on the vase life of the cut gerbera ʻMinouʼ was investigated. To inhibit bacterial proliferation, which is known to shorten vase life, an isothiazoline antimicrobial compound was included in the vase solution. Treatment with GA₃ alone delayed the opening of tubular florets and increased the area of unopen florets, but stem elongation which led to stem bending shortened vase life. Treatment with GA₃ in combination with CaCl₂ suppressed the occurrence of stem bending. Combined treatment with GA₃ and CaCl₂ extended the vase life of cut gerbera more than treatment with CaCl₂ alone. To clarify whether GA₃ delays petal senescence, the effect of GA₃ at 10 and 50 mg·L⁻¹ on petal senescence was investigated using shortened stems. GA₃ at both concentrations significantly delayed petal senescence. Combined treatment with GA₃ and CaCl₂ also significantly extended the vase life of the cut gerbera ʻKimseyʼ and ʻSandyʼ. It was concluded that combined treatment with GA₃ and CaCl₂ is a suitable treatment for extending the vase life of cut gerbera.

Isolation, purification and identification of anthocyanins and flavonols were carried out on flowers of Ranunculus cultivars. Three anthocyanins and 11 flavonols were characterized by chemical and spectroscopic techniques. The anthocyanins were identified as cyanidin 3-O-sambubioside, cyanidin 3-O-(6''-malonylsambubioside) and delphinidin 3-O-(6''-malonylsambubioside). The flavonols were identified as 3-O-glucosides and 3-O-sophorosides of kaempferol and quercetin, and their acylated compounds with malonic acid. Flower colors were divided into six groups, Red-Purple, White, Yellow-Orange, Orange, Red, and Violet groups using the Royal Horticultural Society Colour Chart. The absorption maxima of buffer solutions containing anthocyanins and flavonols isolated in this study were measured to understand the effect of intermolecular copigmentation between these compounds on flower color. The results showed that by addition of 3-O-(6''-malonylglucoside) of kaempferol or quercetin, the absorption maximum of cyanidin 3-O-(6''-malonylsambubioside) or delphinidin 3-O-(6''-malonylsambubioside) shifted bathochromically and exhibited a closer absorption maximum to fresh flower petals than anthocyanin alone. This indicates that the intermolecular copigment effect between anthocyanins and flavonols is responsible for the flower color expression in Ranunculus cultivars.

Capsaicinoids are compounds that generate the characteristic pungent taste of chili peppers, the presence or absence of which determines the utilization of the chili peppers as spices or vegetables. Loss of pungency is a qualitative trait resulting from dysfunction in any of four capsaicinoid biosynthesis genes (Pun1, pAMT, CaKR1, and CaMYB31). However, the lack of pungency in sweet peppers cannot be explained by known mutation alleles in these four genes. Herein, we report a novel dysfunctional allele of Pun1, which encodes acyltransferase 3 (capsaicin synthase), in a Japanese sweet pepper, ‘Sampo Oamanaga’. Firstly, PCR genotyping of ‘Sampo Oamanaga’ Pun1 showed that it was not a known mutant allele. We also performed whole-genome resequencing and found a large genomic deletion around the ‘Sampo Oamanaga’ Pun1 (XM_016704778.1). We then examined the precise size and breakpoint of the Pun1-deletion region via de novo assembly and Sanger sequencing analysis. We found an 18.5-kbp deletion, including the Pun1, on chromosome 2, and we designated this novel allele pun1⁵. The genotypic effects of pun1⁵ were investigated using F₂ progeny derived from a ‘Sampo Oamanaga’ (pun1⁵/pun1⁵) × pungent cultivar ‘Takanotsume’ (Pun1/Pun1) cross. Only pun1⁵-homozygous F₂ plants showed non-pungency; co-segregation between Pun1 genotypes and pungency traits was observed. These results demonstrated that the deficiency of pungency in ‘Sampo Oamanaga’ is associated with the pun1⁵ allele. The present study is the first to discover a large genomic deletion, including a gene among dysfunctional pun1 alleles, and provides new insights into the regulation mechanism of pungency in chili peppers.

We investigated the anthocyanin composition of the purple sweet potato cultivar ‘Churakanasa’. The color tone of the paste was compared by L*, a*, and b* values and ‘Churakanasa’ exhibited a lower b* value, which indicates a bluish tint, than ‘Churakoibeni’, a popular cultivar for paste processing in Okinawa. High performance liquid chromatography (HPLC) analysis of the pigment extract showed that the anthocyanin composition of ‘Churakanasa’ was quite different from that of ‘Ayamurasaki’ and ‘Churakoibeni’. The analysis of the aglycone composition revealed that the cyanidin content (%) of ‘Ayamurasaki’ and ‘Churakoibeni’ contained 19.2% and 22.6% of cyanidins and 80.8% and 77.4% of peonidins, respectively. These findings indicate that these cultivars belong to the peonidin type. In contrast, ‘Churakanasa’ contained 86.4% cyanidin, indicating it to be a cyanidin-type cultivar. The steamed sweet potato paste made from ‘Churakanasa’ (cyanidin type cultivar) exhibited a bluer color compared to the peonidin-type cultivars. This observation suggests a direct correlation between the higher cyanidin content and the blue color intensity of the paste. HPLC-MS analysis of the two major HPLC peaks (peak I and II) of ‘Churakanasa’ suggested that the substance in peak I was YGM-0c; cyanidin-3-p-hydroxybenzoyl sophoroside-5-glucoside by mass, whereas peak II was YGM-1a; cyanidin-3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside. ‘Churakanasa’ exhibits unique color and pigment characteristics as it is the only purple sweet potato cultivar that has YGM-0c and -1a as its primary pigments.