Parthenocarpic apple cultivars have been recognized with simultaneous homeotic floral organ mutations. The mutations included replacements of petals to sepals and stamens to carpels, which were same as the class B mutations of floral organs from Arabidopsis and snapdragon. For apple, the parthenocarpy and class B mutations were tightly inherited and MdPISTILLATA (MdPI) gene deficiency caused homeotic mutations. However, the relationship between the suppression of MdPI and parthenocarpy was unclear. Transgenic apples with suppressed MdPI expression using an anti-sense or co-suppression method were found to have the same homeotic floral organ mutations as parthenocarpic cultivars. Further, the transformants with co-suppression showed parthenocarpy and overexpression of MdPI in fruits prevented normal fruit growth. Other apple MADS genes were analyzed for parthenocarpy. MdMADS13 is classified as another class B gene, which plays a role in floral organ formation together with MdPI. In addition, MdMADS1/8 and MdMADS9 are classified as class E genes, which are could function like SEP1 and 2 genes from Arabidopsis. The MdMADS1/8 and MdMADS9 gene-suppressed apple transformants showed strong inhibition of fruit enlargement, supporting the idea that MdMADS1/8 and MdMADS9 contribute to hypanthium development. It is possible that the MdPI, MdMADS13, MdMADS1/8, and MdMADS9 proteins formed a heterotetramer as a transcriptional regulator and were involved in fruit development. Other plant species such as tomato and grape also showed the respective class B genes affected fruit development. The suppression of tomato class B genes led to class B floral organ mutations and parthenocarpy, and a grape mutant with class B gene expression ectopically inhibited fruit flesh development. Both class B genes seemed to prevent fruit development similar to the apple MdPI. This suggests that the class B genes play not only a role in forming the identities of petals and stamens, but also a pivotal role in fruit development.

Pollination is an important factor affecting fruit development in highbush blueberry (Vaccinium corymbosum L.). In general, planting several different blueberry cultivars increases the chances of cross-pollination and ensures high-quality fruit production. However, little is known about the effects of the pollen source on fruit development in blueberry. The aims of this study were: 1) to understand the effects of the pollen source on fruit size and quality; and 2) to explore the mechanisms underlying fruit development affected by the pollen source. We first characterized the pollination effect on fruit development using 14 different pollination combinations for several years and found that the number of mature seeds and fruit size differed significantly among the fruit pollinated by different pollen sources. Significant correlations between the number of mature seeds and fruit size were found in most combinations, whereas the number of mature seeds was not correlated with other fruit quality parameters such as sugar concentration. Our results and those of previous reports showed that the number of mature seeds, which was influenced by the pollen source, was a primary determinant of fruit size. Time-course observation during fruit development revealed that fruit weight and cell size significantly differed between self-pollinated and cross-pollinated fruit from 30 days after pollination onwards. To explore the molecular mechanisms underlying berry growth affected by developing seeds, we compared gene expression changes between self-pollinated and cross-pollinated fruit. Transcriptome analysis of fruit at 10 days after pollination suggested that auxin signaling pathways were enhanced in cross-pollinated fruit compared with self-pollinated fruit. We thus hypothesize that activated auxin signal transduction underlying early stage seed and fruit development may promote fruit cell enlargement during the early stage of fruit growth in highbush blueberry.

In protected agriculture, optimum temperature management is crucial for enhancing fruit productivity and maintaining cost-effective production. The aim of the present study was to investigate the effects of temperature on peach fruit development and quality. Container-grown ‘KU-PP2’ peach trees grafted on low-chill peach rootstocks were cultivated under controlled conditions at different temperatures (20, 25, and 30°C) during fruit development for two years (2020 and 2021). Fruit growth rates were calculated by measuring fruit diameter every 3 d from fruit setting to first harvest; fruit quality and phytochemistry were analyzed at harvest. Growing temperature markedly affected fruit growth, maturation, and fruit quality. The development of fruit in all treatments exhibited double sigmoid growth curves that included three stages (S1, S2, and S3). Fruit growth rate during S1 and S2 stages was increased, and fruit development period was significantly shortened with an increase in temperature. Contrary to the duration of S3, which was longer at higher temperatures, fruit grown at a high temperature (30°C) ripened by 12–18 days earlier than those grown at low-temperature regimes. In addition, high-temperature conditions were also associated with reduced fruit quality (size, weight, and sweetness), but enhanced development of red coloration. Therefore, even though high-temperature conditions can accelerate early fruit expansion and hasten fruit maturity, such conditions also have negative effects on important agronomic fruit traits.

Gibberellins are widely used to induce seedlessness in table grape production, but are not effective for every cultivar or developmental stage. In order to characterize the potential physiological mechanism behind gibberellin-induced seedlessness, we conducted tissue-specific transcriptome analysis of ovules and ovaries from cultivars with different levels of receptiveness to seedlessness induction. GA₃ treatment at full bloom highly induced gibberellin signaling and various phytohormone signaling pathway genes in ovules at two days after treatment, but had less effect in ovaries, which suggests that GA₃ directly affects seed development. During the development to six days after GA₃ application, cell cycle-related genes in the ovules were markedly downregulated, indicating that this may be related to ovule abortion induction. The marked transcriptomic responses were largely absent in a cultivar with low receptiveness to gibberellin-induced seedlessness, suggesting a crucial role for the observed tissue-specific responses in the successful induction of seedlessness by GA₃ application. Collectively, our transcriptome analysis highlights distinct tissue-specific reactions to GA₃ during early berry development, providing important insights for the successful production of seedless berries by gibberellin application.

In grapes, the ripening time of bunches on lateral or secondary induced shoots, led by simultaneous treatments of current shoot cutting and flower cluster removal, is typically delayed until the cooler seasons. The aim of this study was to estimate the effects of lateral or secondary induced shoot use in the cultivation of ‘Merlot’ grapevine phenology, including number of bunches and weight, yield, and fruit quality. The timings of flowering, coloration and harvest of lateral and secondary induced shoot grapes were delayed by around one month compared with those of vines grown under standard cultivation, which were used as a control. However, there were substantial differences between treatments in terms of number of bunches and weight, yield, and fruit quality. When lateral shoots grew after the current shoot was cut and the flower clusters were removed, the number of bunches decreased, and yield was significantly reduced. In contrast, when the secondary induced shoot germinated after the current shoot, flower clusters, and growing lateral shoots were removed, a stable number of bunches was observed and there was not a severe decrease in yield. Skin anthocyanin content in both the lateral shoot and secondary induced shoot grape berries was increased compared with control. This effect was comparatively stronger in secondary induced shoot grapes subjected to comparatively lower air temperatures during ripening. The results of this study underscore the importance of discriminating between lateral and secondary induced shoots in the process of shifting grape ripening to a cooler season by removing current shoots and flower clusters.

Walnut (Juglans regia L.) is a major nut crop of the Juglandaceae family and is well-known for its high nutritional value, which is achieved by a rich array of polyphenolic compounds. Phenolics are considered beneficial to human health because of their antioxidant, antimutagenic, and free radical scavenging properties. However, the phenolic biosynthetic pathway in walnut remains poorly studied. In this study, we cloned a 5-enolpyruvylshikimate 3-phosphate synthase (JrEPSPS) gene from walnut, a key gene involved in the shikimate pathway that catalyzes the penultimate step of the shikimate pathway toward the biosynthesis of aromatic amino acids. Subsequent sequence analysis revealed that the JrEPSPS protein harbors an N-terminal helix-turn-helix-like motif, which is known to mediate EPSPS function by acting as a transcription factor and regulating the expression of genes in the phenylpropanoid pathway in poplar. Subcellar localization analysis suggested JrEPSPS was localized in chloroplasts. The transient overexpression of JrEPSPS in persimmon (Diospyros kaki Thunb.) leaves and fruit discs showed significantly increased phenolic accumulation by elevating the expression of phenolic biosynthetic pathway genes. These results provide novel insights into the roles of EPSPS involved in phenolic biosynthesis in plants.

The accumulation of abscisic acid (ABA) is considered a crucial signal for the onset of berry maturation in grape berry, including ‘Kyoho’ (Vitis labruscana L.). Therefore, the delay of grape berry maturation, especially of peel coloration, by applying an ABA inhibitor (nordihydroguaiaretic acid, NDGA) to berry clusters has been investigated in various studies. Herein, we report for the first time that NDGA treatment on leaves inhibited the accumulation of both ABA, and genes related to ABA signal transduction, in berry peels and triggered the inhibition of anthocyanin and the accumulation of sucrose. We also found that changes in the expression patterns of genes related to anthocyanin and sucrose biosynthesis were concomitant with changes in anthocyanin and sucrose accumulation. Finally, RNA sequence analysis showed that NDGA treatment on leaves changed the expression of genes related to internal oxygen levels in berry flesh, which is known to affect cellular alcohol dehydrogenase activity. In this study, we measured changes in the concentrations of alcoholic and alcohol-derived aroma volatiles such as hexenal and phenylethyl alcohol, and found that NDGA treatment on leaves inhibited the maturation of berry peel and flesh. These results suggest the possibility of ABA signal transduction from leaves to berries.

In this study, after developing a method for predicting full bloom dates of ‘Kyoho’ grape by incorporating ‘Kyoho’ growth characteristics at multiple sites in Japan into one model, we evaluated the prediction accuracy of the model. Using data of bud break dates and full bloom dates of ‘Kyoho’ at 14 public test sites from 2000–2018, we investigated the grape development characteristics at the sites. The conventional effective accumulated temperature model relies on the assumption of a linear relation between temperature and grape development. However, based on results of grape development characteristic analyses, we formulated new prediction models that include the following considerations: 1) a nonlinear relation between temperature and grape development, 2) effects of solar radiation on grape development, and 3) relations between Day of Year (DOY) of bud break date and grape development. Prediction analyses of two types were applied to full bloom dates at the 14 sites using the effective accumulated temperature model and our model, which includes the three considerations above simultaneously. For the first analysis, after estimating the model parameters for each site using data observed at that site, we predicted full bloom dates there. Evaluation of the prediction accuracy using leave-one-out cross validation revealed that the average root mean square error (RMSE) for all sites was 2.24 days for the effective accumulated temperature model. For our model, it was 2.06 days. The model had higher prediction accuracy at multiple sites. For the second analysis, we used the model parameters for each site based on data collected at all sites except the site in question. The average RMSE for all sites was 2.76 days for the effective accumulated temperature model and 2.54 days for our model. These results suggest that our model of ‘Kyoho’ growth characteristics at multiple sites can predict full bloom dates with higher accuracy than the effective accumulated temperature model.

Dissatisfaction with the flavor quality of young aromatic Thai coconut ‘Nam-Hom’ usually grows when stored at 2–4°C after harvest, represented by off-flavor development and aroma loss. To understand the mechanism of postharvest flavor deterioration, young coconut fruit were stored at 4°C and 25°C for 15 days. Sensory evaluation was performed, volatile compositions were analyzed, enzyme activities and transcript levels of genes related to the synthesis of volatiles were investigated. Off-flavor was observed after six days of storage at 4°C and tended to be more serious after that. A total of 45 volatiles were identified in the young coconut fruit. Partial least square discriminant analysis (PLS-DA) revealed two volatiles, 1-heptanol, 1-octanol, and nonanal, which were associated with off-flavor development. Transcript levels of CnLOX1, CnHPL1, and CnADH2, relating to the volatile production catalyzed by the LOX pathway, increased during storage at low temperatures. Their respective enzyme activities were also found to increase. The loss of the aromatic nature of young ‘Nam-Hom’ coconut at 4°C was found to be associated with an increase in CnBadh2 gene expression, resulting in a lower 2-acetyl-1-pyrroline (2-AP) content as compared to that at 25°C. Wrapping the fruit with polyethylene (PE) instead of polyvinyl chloride film reduced the off-flavor by reducing the oxygen concentration; consequently, this prevented enzyme activities and expression of genes from the LOX pathway. However, the loss of the aromatic nature of young ‘Nam-Hom’ coconut fruit at low temperature storage could not be mitigated with PE packaging.

Fruit mass is an important factor for determining the yield of tomatoes (Solanum lycopersicum), with higher mass being an important objective. Most fruit traits, including fruit mass, are quantitative, and numerous quantitative trait loci (QTL) control these traits. Previous studies investigating tomato introgression lines (ILs) revealed several QTLs for fruit yield, and suggested that IL12-1 is a potential line to increase fruit mass. Our aim was to facilitate genetic studies of the diverse characteristics of wild relatives of tomato. Therefore, tomato ILs from a cross between Solanum pennellii and the cultivar S. lycopersicum ‘M82’ were used. ILs that carry a S. pennellii chromosome segment on chromosome 12 of ‘M82’ were evaluated further for fruit mass expansion and regulation. IL12-1-1, a subline of IL12-1, was found to produce large ripening fruits compared with ‘M82’, a phenotype that resulted in increased pericarp thicknesses. To investigate the physiological mechanisms contributing to the increased fruit mass of IL12-1-1, the cell counts of fruit pericarp tissues during fruit development were evaluated. Cell numbers of IL12-1-1 fruit pericarp at 20 days after flowering were higher than those of ‘M82’, a difference that most likely occurred during the cell division phase. In addition, the levels of the phytohormones auxin and cytokinin, which are known to be related to cell division of the fruit tissue, were higher in IL12-1-1 compared with ‘M82’. Therefore, differences in these phytohormones between ‘M82’ and IL12-1-1 may be affected by the number of cells in the pericarp tissues. Expression analysis of Solyc12g005250 (SlKLP) and Solyc12g005310 (SlGH3-15), which are located in the IL12-1-1 region of the S. pennellii chromosome, showed significant differences between ‘M82’ and IL12-1-1 during the cell division phase; a better understanding of IL12-1-1 cellular and molecular features can contribute to the breeding and increased production of tomato crops.

This study investigated genetic polymorphism related to anthocyanin composition variation in lisianthus (Eustoma grandiflorum) flower petals. Three different bands were detected by genomic polymerase chain reaction using specific primers based on the reported flavonoid 3',5'-hydroxylase (F3'5'H) gene sequence. Our genetic study revealed that they were allelic. They were named F3'5'H1-1, F3'5'H1-2, and f3'5'h1-2. F3'5'H1-1 and F3'5'H1-2 differed in the length of the intron. Allele f3'5'h1-2 possessed a retrotransposon insertion in the first exon, but otherwise, its gene sequence was almost identical to that of F3'5'H1-2. This retrotransposon is a Ty1-copia type retrotransposon and was designated as the retrotransposon of Eustoma grandiflorum 1 (rTeg1). The mauve flower line ‘ME’ and red-purple flower line ‘PRP’ were homozygous for F3'5'H1-1 and mostly accumulated cyanidin, with a small amount of delphinidin, in flower petals (the Cy major phenotype). The violet flower line ‘RV’ was homozygous for F3'5'H1-2 and accumulated only delphinidin (the Dp major phenotype). The pink-red flower line ‘AK’ was homozygous for f3'5'h1-2, accumulated pelargonidin, and lacked delphinidin (the Pg major-non Dp phenotype). Segregation analysis of the F₂ population from ‘ME’ × ‘RV’ revealed that F3'5'H1-2 was associated with the Dp major phenotype, and the delphinidin major trait was dominant in the Cy major phenotype. All the Cy major phenotype plants in the F₂ population possessed homozygous F3'5'H1-1. Genetic analysis of the F₂ population from the cross between delphinidin-containing and delphinidin-lacking strains revealed that the homozygous f3'5'h1-2 genotype co-segregated with the Pg major-non Dp phenotype, which was recessive to the delphinidin-containing phenotypes. Expression analysis of the F3'5'H gene demonstrated that an abnormal mRNA was transcribed from the F3'5'H gene in the homozygous f3'5'h1-2 line by the insertion of rTeg1. Therefore, these F3'5'H gene polymorphisms can be used as DNA markers for breeding lisianthus based on flower color.