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.

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.

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.

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.

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.

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.