The effect of short-term anoxic treatment prior to storage at ambient and cool temperatures on pericarp browning, fruit quality, secondary metabolites, antioxidant activity, and the browning enzyme of litchi (Litchi chinensis Sonn.) cv. Hong Huey were investigated. Litchi fruit were exposed to anoxic conditions for 6, 12, 18 and 24 h before storage at 28 ± 2°C for 5 days, or at 7 ± 2°C for 14 days. Anoxic treatment resulted in significantly decreases in electrical conductivity, weight loss, browning index, while maintaining the total soluble solids (TSS) and delaying increases in polyphenol oxidase (PPO) and peroxidase (POD) activities compared with control fruit. Furthermore, anoxic treatment increased litchi pericarp methanol extract antioxidant capacity, as measured by free-radical scavenging activity. This is associated with greater amounts of ascorbic acid, anthocyanins, and phenolic/flavonoid components as compared with control fruit. Additionally, anoxic treatment considerably delayed litchi fruit pericarp browning. This suggests that with adequate short-term anoxia duration, an enhanced non-enzymatic antioxidant process may directly or indirectly delay litchi pericarp browning. Thus, a short anoxic treatment enables harvested litchi quality to be sustained at ambient and cool temperatures. This non-chemical and inexpensive treatment deserves further development and application, especially in commercial distribution systems where cooling is insufficient.

Abiu is a tropical fruit with many beneficial bioactive compounds. However, its economic value is limited by a short shelf life and rapid browning. This study evaluated the effect of ascorbic acid on extending abiu fruit shelf life during storage. The fruit was soaked in ascorbic acid solutions of 0 mM (control), 5 mM (AA5), and 10 mM (AA10) for 10 minutes, air-dried, then stored in an ambient room (28 ± 1°C and 80 ± 5% RH) for 12 days. The results indicated that the 10 mM exogenous ascorbic acid treatment increased abiu fruit shelf life up to 12 days, nine days longer than the control. Abiu fruit, after the AA10 treatment, underwent a 1.4-fold lower weight loss than the control. In addition, on day 12 of storage, the browning of fruit with the AA10 treatment were 8 and 11% on the peel and pulp, respectively. The climacteric peak of abiu fruit in the AA10 treatment occurred on day 8 of storage, three days later than the control. The AA10 treatment also maintained vitamin C content and fruit firmness. Thus, the AA10 treatment effectively extended shelf life and maintained abiu fruit quality.

Pineapples (Ananas comosus (L.) Merr.) are harvested throughout the year, with acid and soluble solid contents varying with season. However, there is a lack of knowledge about the relationship between the acid and soluble solid content and climatic factors. To investigate these relationships, we analyzed the acid and soluble solid content records of a large number of fruit harvested over 15 years from three production areas in Japan. Over the warm period (June to September) pineapple acid content was low, while over the cool period (December to April) it was high, regardless of the cultivar. Soluble solid contents were highest in June and lowest between September and March. Acid content at harvest inversely correlated with the temperature immediately before harvest, and the relationship modelled linearly with the mean temperature over the 10 or 20 days before harvest as a variable. The acid content of ‘N67-10’ is highly dependent on temperature, while that of ‘Okinou P17’ is stable regardless of temperature. The soluble solid content was affected by temperature over longer periods than the acid content and was modelled using a quadratic equation with the mean temperature over the 70–120 days before harvest as a variable. The approximate curve of soluble solid content peaked around 23°C. The majority of ‘Okinou P17’ fruit yielded a soluble solid content of > 15 °Brix over a wide temperature range (≥ 19°C), while the temperature at which most ‘N67-10’ fruit had soluble solid of > 15 °Brix was limited to a narrow range (22–23°C). Although the coefficients of both model equations were significant for all cultivars, the R² of soluble solid content was smaller than that of acid content. These results contribute to understanding the relationship between acid and soluble solid content and temperature.

The large berry mutant (LBM) of the ‘Delaware’ (V. vinifera × (V. labrusca × V. aestivalis)) is known to produce larger berries than ‘Delaware’ when subjected to traditional double gibberellic acid-3 (GA₃) treatment. In this study, we first compared ‘Delaware’ and the LBM in terms of their berry and cluster quality to reevaluate previous findings on LBM. Next, we compared berry size without GA₃, histological characteristics of the early developmental berry, and then GA-related gene expression to reveal the characteristics of the LBM. The previous finding that LBM yielded larger berry sizes than ‘Delaware’ with double GA₃ treatment was verified, but without GA₃ treatment, LBM did not produce larger berries than ‘Delaware’. This highlights the prerequisite of exogenous GA for larger berry size in LBM. Histological analysis revealed an increase in cell numbers of the inner and outer mesocarp walls in the early developmental stage of LBM berries. Gene expression analysis of the flower buds and berries indicated an increased expression of VvGID1A, encoding the GA receptor, in LBM than in ‘Delaware’ 3 h after the first GA₃ treatment. Additionally, the expression of VvGID1A and VvGID1B was higher in LBM than that in ‘Delaware’ before and after the second GA₃ treatment. The expression of VvGID2A, which interacts with the GA receptor and promotes GA signaling, was also higher in LBM than in ‘Delaware’ before the first GA₃ treatment. However, the expression of VvSLR1, VvGAI1, and VvGAI2 that encode DELLA proteins, essential negative regulators for GA reactions, mostly showed no significant changes. These results suggest that LBM berries had higher GA sensitivity than the ‘Delaware’. Based on these results, we believe that the larger berry size in LBM may be due to increased cell numbers resulting from high GA sensitivity.

Shoot regeneration experiments from growth-point-derived callus were conducted to improve apple genome editing techniques. The plant material studied was in vitro maintained shoots of ‘Fuji’. In the first step, a procedure for shoot formation from apple callus was established. After using the two earlier reported cases’ experimental procedures and media compositions, we investigated the effect of media variations in callus induction, callus multiplication, and shoot induction from the meristem. The procedure that yielded a higher shoot regeneration rate with meristem-derived callus involved shoot multiplication with 1001 medium followed by the Caboni’s callus induction medium, then without callus propagation on liquid medium, and then either Caboni’s or Saito-Suzuki’s shoot induction medium. In this experiment, axillary buds may remain as the shoot apexes were excised at 1 mm. In the next experiment, shoot apexes were excised at 0.5 mm to completely eliminate the axillary bud. Then treatment in the dark was added to the procedure to further improve shoot regeneration rates for the meristem-derived callus. Shoot multiplication medium and shoot induction medium procedures were conducted under dark conditions. This yielded the following optimal procedure: excising meristems from chlorosis shoots after 2–3 months of dark treatment in shoot multiplication medium on 1001; placing the excised meristems in Carboni’s callus induction medium in the dark for 20 days; then transferring the formed callus Saito-Suzuki’s shoot induction medium with incubation in the dark for at least 2 weeks. The shoot regeneration rates of calli treated in the dark for 6 weeks with shoot induction medium reached 68%. Relative to previous reports, this value is considered high for shoot regeneration from calli in apple cultivars.

Postharvest loss of mango often occurs due to the short harvesting period. An experiment was conducted to determine the impact of paclobutrazol (PBZ) and flower bud pruning (FBP) on regulating flowering, fruiting time and fruit quality of ‘Amrapali’ mango. Different doses of PBZ at 0.5, 1.0, 1.5, 2.0 g per meter canopy diameter and water application along with FBP or without FBP were used, as well as water application without FBP (control). The application of PBZ caused earlier flowering by 22 days and harvesting was also done earlier by 18 days compared to the control. Plants subjected to FBP with PBZ reflowered 36 days later and harvesting was delayed by 16 days compared to the control. Moreover, the combination of PBZ 1.5 g with FBP showed significantly higher flowering percentages, number of panicles, total flowers, total fruits and weight of fruit compared to the control. In addition, the application of PBZ 1.5 g with FBP increased the total soluble solids, reducing sugar, non-reducing sugar, total sugar and β-carotene, while it decreased the vitamin C content. The present findings imply that applying PBZ 1.5 g with FBP to mango can extend the flowering and fruiting time, while the fruit quality was also influenced positively.

Evaluating the function of genes expressed in fruit tissues of fruit tree species using a genetic transformation approach is a long process because the trees are generally recalcitrant to genetic transformation and cannot bear fruit during their long juvenile phases. Transient gene expression in fruit enables the functional analysis of genes associated with fruit traits, which may accelerate the study of fruit physiology. Here, by using the recently developed “Tsukuba system”, we successfully established an efficient transient expression system in harvested fruit tissues. The “Tsukuba system” utilizes a combination of the geminiviral replication system and a double terminator, which ensures sufficient levels of transgene expression. We used blueberry fruit as a model to characterize the applicability of this system for transient expression in fruit tissue. The pTKB3-EGFP vector was introduced by agroinfiltration into the fruit tissues of several blueberry cultivars. We found that transient GFP fluorescence in fruit peaked 4–6 days after agroinfiltration. Agrobacterium suspensions were easily injected into soft, mature fruit, and GFP was strongly expressed; however, hard, immature fruit were not penetrable by Agrobacterium suspensions, and GFP was rarely detected. We then tested the applicability of the developed system to other fruit tree species: six families, 17 species, and 26 cultivars. GFP fluorescence was detected in all species, except for Japanese apricot. In blueberry, bilberry, sweet cherry, apricot, and satsuma mandarin, GFP was highly expressed and observed in a large proportion of the flesh. In kiwifruit, hardy kiwifruits, persimmon, peach, apple, European pear, and grape, GFP fluorescence was limited to certain parts of the fruits. Finally, transient VcMYBA1 overexpression in blueberry was tested as a model for gene functional analysis in fruit. Transient VcMYBA1 overexpression induced red pigmentation in the flesh, suggesting that VcMYBA1 expression caused anthocyanin accumulation. This study provides a technical basis for the rapid evaluation of genes expressed in fruit, which will be useful for gene function evaluation studies in fruit crops with long juvenile phases.

Garland chrysanthemum is conventionally ratooned and harvested by selective hand picking. This manually intensive mode of harvesting may be improved by adopting mechanized harvesting practices. In view of incorporating machine harvesting into garland chrysanthemum crops, this study evaluated the effects of plant and cutting height on ratoon crop regrowth. Garland chrysanthemums were horizontally harvested using six combinations of three plant height levels at harvest (20 cm, 30 cm, and 40 cm) and three cutting height levels (5 cm, 10 cm, and 15 cm) over three repeated harvests. Plant height at harvest as well as the cutting height affected the total ratooning yield and regrowth process. If plant heights at harvest were low (20 cm) or cutting height relative to plant height at harvest was excessively high, yields decreased. Higher plant heights at harvest and lower cutting heights resulted in longer regrowth periods. Evaluation of branch structures revealed that low cutting heights decreased the number of branches and nodes remaining for regrowth. If the plant height at harvest was low (20 cm), node numbers tended to decrease. Excessively high cutting heights relative to plant height at harvest potentially results in the harvest of immature leaves and stems. We determined that harvesting at 30 cm plant height with 10 cm cutting height was suitable for ratooning, and resulted in high yields. This combination resulted in a sufficient number of first lateral branches and nodes on the plants, thus enabled the harvest of fully grown leaves.

In Japan, broccoli (Brassica oleracea L. var. Italica) is primarily harvested manually. Some Japanese broccoli cultivars have short stems, but these broccoli heads are more difficult to harvest, and complicate the introduction of mechanical harvesters. Therefore, research is focused on strategies to control stem length. The present study examined the effects of the plant hormone gibberellin (GA) on the morphological and agronomic traits of broccoli shoots. The broccoli cultivar ‘SK9-099’, widely distributed in Japan and characterized by a short stem, was studied. These experiments were conducted over three cropping seasons, i.e., spring (Exp. 1), summer (Exp. 2), and fall (Exp. 3), with four GA treatment plots at 0 ppm (Control), 20 ppm, 100 ppm, and 500 ppm. This study observed that, on average, GA elongated stem length from approximately 16.0 cm in the control plot to 24.7 cm in the 500 ppm plot for the three cropping seasons, without decreasing yield. In addition, GA treatment accelerated apical bud growth and shortened the overall growth period by 16 days in the 500 ppm plot compared to the control in the fall, equivalent to 20.5% of the growth period from transplantation to harvest in the latter.

This study highlights several practical benefits of GA application for growers, minimizing manual harvesting labor, avoid the difficult of designing mechanical harvesters for short-stemmed cultivars, and increase field usage efficiency by shortening the growth period.

Purple sweet potatoes are rich in the purple pigment anthocyanin. In recent years, it has been reported that the anthocyanin content of the same variety varies depending on the place of production. Therefore, to investigate the effect of soil temperature on the anthocyanin content of sweet potato tuberous roots, two types of covering materials, black and white mulch films, were used in the same field. The vines were planted in May, June and July; the cultivation period was set to 120–180 days and tuberous roots were harvested in September, October and November. The average soil temperature ranged from 22.9 to 26.5°C, with the white mulch having lower soil temperatures than the black mulch. The tuberous root yield increased with longer cultivation periods; the tuberous root yield in the May–November plot with a 180-day cultivation period was about twice that of the June–October and July–November plots with a 120-day cultivation period. The anthocyanin content of the tuberous root was negatively correlated with the average soil temperature; the test plots harvested in November had a higher anthocyanin content than the other test plots. In particular, the anthocyanin content of sweet potato cultivated in white mulch in July–November was about twice that cultivated in May–September. Although the factors that increase the tuberous root yield (prolonged cultivation period) are different from those that increase the anthocyanin content (lower temperature range), the tuberous root yield showed a larger effect on the total anthocyanin yield. Since the cultivation period needs to be prolonged to increase tuberous root yield, it would consequently increase the anthocyanin yield. The quality of the harvest was better under lower soil temperature as it led to an increase in the anthocyanin yield. Therefore, it was suggested that anthocyanin yields could be maximized by extending the growing season and harvesting at lower soil temperatures.

Melon Fusarium wilt, caused by Fusarium oxysporum f. sp. melonis (Fom), is one of the most prevalent fungal diseases affecting melon (Cucumis melo L.). We aimed at finding an effective resource for breeding cultivars tolerant to Fom race 1.2, which includes pathotypes that cause yellowing (race 1.2y) and wilting (race 1.2w). We screened 294 melon accessions that originated mainly in Africa and Asia for tolerance to race 1.2y. The highest level of tolerance was observed in the Indian accession PI124550; one of the five PI124550 plants tested showed no disease symptoms. From this plant, a tolerant inbred line, YR01, was developed after seven rounds of selfing combined with selection for tolerance to race 1.2y. YR01 had a high level of tolerance not only to race 1.2y, but also to race 1.2w. It was more tolerant to race 1.2y than the tolerant reference control ‘Isabelle’ and was equally tolerant to race 1.2w. Analysis of F₁ hybrids and an F₂ population developed by crossing YR01 with susceptible ‘Earl’s Favorite Harukei 3’ suggested that YR01 had multiple recessive and dominant (or codominant) genes for tolerance to race 1.2y and one dominant gene for tolerance to race 1.2w. These results indicate that PI124550 and its derivative YR01 are a promising breeding material with novel genes conferring practically useful tolerance to both pathotypes of race 1.2.

Genetic improvement of flower vase life is an important breeding target for ornamental plants. As the vase life of cut dahlia (Dahlia variabilis) flowers is very short, we initiated a conventional crossbreeding research program in 2014 to improve it. We evaluated the vase life of dahlia seedlings during summer (from July to early September) to develop dahlias that grow and bloom under high temperatures and have excellent vase life for Japanese summer conditions. Crossing and selection over five generations greatly improved vase life. The mean vase life increased from 4.4 days in the 1st generation, derived from 22 parental cultivars, to 8.0 days in the 5th generation, a net increase of 3.6 days. Mean vase life increased significantly by 1.6 days from the 4th to the 5th generation, indicating continued improvement. The mean vase life of the 12 lines selected from the 3rd and 4th generations ranged between 6.0 and 15.9 days in distilled water and from 7.8 to 14.6 days in GLA solution (10 g·L⁻¹ glucose, 0.5 mL·L⁻¹ CMIT/MIT [isothiazolinone derivatives], and 50 mg·L⁻¹ aluminum sulfate). Vase life was further extended by 0.5 to 4.0 days using 6-benzylaminopurine (BA) sprays compared to GLA alone. In particular, the 4th-generation line 003-15 vase life was 13.8 to 15.9 days (2.5× that of ‘Kamakura’, a leading white dahlia cultivar in Japan) in distilled water, 12.0 to 14.6 days (1.8× to 2.2×) in GLA, and 13.9 to 15.3 days (1.7× to 1.9×) in GLA+BA in winter and spring. Cut flowers of line 003-15 harvested under high temperatures in July–August and at 28°C with GLA treatment also had long vase life. The pedigree of line 003-15 suggests that genes related to long vase life derived from ‘Micchan’ (with a long vase life) may have accumulated or duplicated in line 003-15. Finally, four selected lines, including 003-15, had high ethylene sensitivity, as 10 μL·L⁻¹ ethylene treatment caused petal abscission in 2.0 to 2.8 days.

The flower colors and flavonoids of 16 cultivars of Verbena hybrida Groenl. & Rumpler (Verbenaceae) were examined to evaluate the relationship between flower color and flavonoid components. Fifteen anthocyanins {3-O-glucoside, 3,5-di-O-glucoside, 3-O-[6-O-(acetyl)-glucoside], 3-O-[6-O-(malonyl)-glucoside], and 3,5-di-O-[6-O-(acetyl)-glucoside] of delphinidins, cyanidins, and pelargonidins}, seven flavones {7-O-(glucuronide) of apigenin, luteolin, tricetin, and 4'-O-methyl-luteolin, 7-O-[2-O-(glucuronosyl)-glucuronide]-4'-O-(glucuronide) of apigenin, and 7-O-[2-O-(glucuronosyl)-glucuronide] of apigenin and luteolin}, two flavonols {3-O-glucoside and 3-O-[6-O-(acetyl)-glucoside] of kaempferols}, and chlorogenic acid were isolated from the flowers of these cultivars. Their structures were identified using co-HPLC, nuclear magnetic resonance, and mass spectrometry. For the Red to Purple-Violet cultivars, the corresponding color chart names were responsible for the major anthocyanidin types, and the hue values (b*/a*) of these flower colors reflected the anthocyanins concentration. Based on the relationship between the distribution of flavones, flavonols, and chlorogenic acid among cultivars and flower color, we conclude that flavonoids other than anthocyanins and chlorogenic acid make little contribution to flower color. The yellowish red color is thought to be affected by carotenoids.

The most popular fragrant cut rose cultivar in Japan is ‘Yves Piaget’, but its petals often become malformed after harvest. These malformed flowers, referred to as “incurved flowers”, are characterized by petals curving toward the adaxial side which prevents normal flowering and significantly decreases the cut flower quality. It has been reported that jasmonic acid (JA) affects petal growth, and could suppress the emergence of incurved flowers. Therefore, in this study, we investigated the use of exogenous JA, methyl jasmonate (MeJA), applied to cut flowers of ‘Yves Piaget’ by 24 h pulse-uptake treatment. Results showed that 500 μM MeJA 24 h pulse-uptake treatment was effective at suppressing the number of incurved petals. Then, salicylic acid (SA), an antagonist of JA, was applied to see if the number of incurved petals increased. We compared three treatments: deionized water uptake treatment (control), 500 μM MeJA pulse-uptake treatment, and 500 μM SA continuous-uptake treatment. Vase life did not differ significantly between the three treatments, but the 500 μM MeJA pulse-uptake treatment produced a better-preserved flower shape due to only slight petal bluing and discoloration. In contrast, the control and 500 μM SA continuous-uptake treatments produced cut flowers with major petal wilting, bluing, and discoloration. The 500 μM MeJA pulse-uptake treatment tended to extend the number of days from flower bud to full bloom and decrease the number of incurved petals due to the continued high-water absorption. The commercial value of roses lies in the blooming process from bud until full bloom; the increased number of days from bud to full bloom after 500 μM MeJA pulse-uptake treatment improved the cut flower quality. In contrast, there was less water absorption and more incurved petals in the days after the 500 μM SA continuous-uptake treatment, indicating an antagonistic response to the 500 μM MeJA pulse-uptake treatment. In conclusion, treatment of ‘Yves Piaget’ cut flowers with 500 μM MeJA pulse-uptake could decrease the number of incurved petals and improve the cut flower quality.

We investigated bluish-purple Platycodon grandiflorus flowers for yet unidentified flavonoid-related compounds and their flower coloration mechanisms. We identified a new polyacylated anthocyanin, delphinidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[6-O-(4-O-(6-O-(4-O-(6-O-(4-O-(β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranoside] (3) as the minor anthocyanin component along with four known anthocyanins, four known flavones, and chlorogenic acid. The major anthocyanin of the bluish-purple P. grandiflorus flowers is platyconin. While platyconin has two caffeic acids linked in series via glucose molecules at the 7-position of delphinidin, anthocyanin 3 has three caffeic acids linked in series via glucose molecules at the 7-position of delphinidin. To investigate the effects of the number of aromatic acyl groups in polyacylated anthocyanin on bluing and stability, the color and stability of anthocyanin 3 in diluted aqueous solution (5 × 10⁻⁵ M) at a weak acidic condition (pH 5.7, the same pH as the petal sap) were compared with those of platyconin. Results showed that even if the three caffeic acids were bound in series at the 7-position of delphinidin, there was no further bluing or stabilizing effects of anthocyanin 3 compared to platyconin, but a tendency toward weakening color intensity was observed. Investigation of the change in anthocyanin content at the flower developmental stages showed that delphinidin 3-rutinoside-7-glucoside, which is the deacylated form of platyconin, first accumulated up to sufficient amounts at the bud stage, followed by an increase in platyconin content. At the bud stage, the petals were not purple or violet, except for veins, despite the presence of a good amount of delphinidin 3-rutinoside-7-glucoside, indicating the delphinidin 3-rutinoside-7-glucoside was present in some colorless state.

Tulip (Tulipa gesneriana L.) cultivars exhibit diverse floral scents, the emissions of which are generally influenced by temperature. To fully benefit from these scents and add value to cut tulips, it is necessary to evaluate the scent emission response to temperature. This study investigated the daily emission changes of 82 volatiles, including the main scent compounds, at different temperatures (13, 18, and 23°C), in the cut tulips from eight tulip cultivars with different scents. At 23 and 18°C, the total scent emissions of each cultivar increased with flower opening and subsequently decreased with visible senescence. Floral senescence progressed more rapidly at 23°C, and the decrease in total scent emission occurred most rapidly at 23°C. Scent emissions at 18°C tended to be lower than at 23°C. The vase life of the cut tulips was most prolonged at 13°C owing to the slow senescence; however, scent emissions remained low after the flower opening. These results indicate that improving both tulip scent emission and vase life under constant temperature conditions is difficult. It was observed that scent composition changed before and after flower opening, and with floral senescence. In contrast, temperature had little effect on scent composition. Cut tulips stored at a low temperature (10 or 15°C) over four and a half days and then transferred to room temperature (20°C) had a longer vase life than tulips maintained at room temperature, due to delayed senescence. In addition, scent emissions were low at low temperatures, but increased rapidly upon transfer to room temperature. Therefore, storage of cut tulips at low temperatures may lead to increased scent emissions upon transfer to room temperature. These findings imply that low-temperature storage of cut tulips before sale contributes to both vase life and a rich scent after sale. The results reported here demonstrate the improvement of cut tulip scent emissions by appropriate temperature management.