Self-compatibility is an important trait in plant breeding and genetics. To overcome self-incompatibility (SI) in Prunus × yedoensis ‘Somei-yoshino’, one of the most popular flowering cherry cultivars in Japan, we examined pollen tube growth and adaptability after bud pollination (BP), stigma excision (SE), and hot water immersion (HI: 40°C for 1 min, 40°C for 3 min, 45°C for 3 min, and 50°C for 3 min) treatments. On SE treatment, only a few pollen grains adhered to the cutting surface of the style, and sufficient pollen tube growth was not observed. After BP and HI at 40°C, self-pollen tube growth was arrested at a depth of approximately 4 mm from the stigma, at the center of the style, and it was similar to that of the control pollination (P > 0.05). Thus, these methods were not suitable for overcoming SI in ‘Somei-yoshino’. On the other hand, an increase in self-pollen tube growth (P < 0.001) was observed after HI treatment at 45°C (6.9 mm) and 50°C (8.6 mm), where some of the pollen tubes extended to the bottom of the style. Thus, HI (over 45°C) enabled pollen tube growth in the self-styles, thereby overcoming SI in ‘Somei-yoshino’. However, all flowers subjected to HI treatment at 45 and 50°C had necrotized a few weeks after pollination.
The induction of polyphenol oxidase (PPO) gene mutation through ion beam irradiation of protoplasts was attempted for the production of lettuce plants with a low browning property as a cut vegetable. It was clarified that the optimum protoplast density was 0.63–0.75 × 104 mL–1 for shoot regeneration from protoplasts of lettuce ‘Round’. Effects of 12C6+ ion beam irradiation on the growth of protoplasts were investigated, and the percentage of colony formation decreased as the irradiation dose increased. The dose leading to 50% cell growth as compared with the untreated control was approximately 3.3 Gy. Two out of 869 calli irradiated with 12C6+ ion beams were found to be PPO gene mutations by the TILLING method. PPO activities of the regenerated plants from the two mutant calli named 2Gy-3-36 and 5Gy-2-27 were preliminarily assayed, and lettuce plants from 2Gy-3-36 exhibited half of the PPO activity as compared with the non-irradiated controls. A part of the M2 population from 2Gy-2-36 exhibited the property of no band of heteroduplex cleavage by Cel I, with markedly low PPO activity as the control.
Six offspring in each of 24 families and their parents in Japanese pear were evaluated regarding the fruit ripening time. Analysis of variance for the offspring, which estimated between- and within-family variance, and the regression of the mean value in a full-sib family on the mid-parental value (MP) revealed that the genetic differences among families could be explained mostly by MP, indicating that they were under additive genetic control. Genotypic values of offspring in a family were assumed to be normally distributed around the regression line with the sum of within-family genetic variance and the variance due to the deviation of the family-mean from the regression line. Based on the parental mean performance of 10 fruit on a single tree for six years, the coefficient of regression of mean values in a full-sib family on MP was 0.8072 ± 0.02 (SE), and the proportion of offspring with genotypic values leading to ripening earlier than middle-August was estimated at 7 and 0.7% for the two sets in the case of MP = 2.7 and 3.55, respectively.
We studied the self-pollination fruition rate of subvars of the original Japanese pear ‘Osa-nijisseiki’ (‘Akibae’, ‘Akikansen’, ‘Natsusoyoka’ and ‘Shinmizuki’) by examining plants at 4 and 16 weeks after pollination over three years. Findings showed that after 4 weeks of pollination, the fruition rates among the cultivars differed significantly. Among the four cultivars, the fruition rates of ‘Akibae’ and ‘Natsusoyoka’ were low. The fruition rates of these cultivars further declined from 4 to 16 weeks after pollination. Next, we found that there were similar trends with the self-pollination test in mutual pollination tests. In order to determine the reason for the difference in self-pollination fruition, we examined pollen tube growth 72 hours after pollination. We found that in ‘Akibae’ and ‘Natsusoyoka’, the cells of transmitting tissue had been destroyed, resulting in a hollow tube. Thus, the destruction of pollen tubes may contributes to accelerating the rate of pistil aging in ‘Akibae’ and ‘Natsusoyoka’, thereby, leading to a shorter pollination period and low fruition rate for self-pollination.
The effects of the nutrient solution concentration on the rooting and growth of cuttings in Elatostema involucratum Franch. & Sav. cultured by hydroponics were investigated. The rooting rate of cuttings cultured at nutrient solution concentration of 0.1 and 0.25 units (0.5 and 0.8 dS・m–1, respectively.) was equal to or more than that of cuttings cultured at 0 units. The rooted cuttings cultured at a concentration of 0.1 units showed faster growth during the nursery period and after transplantation than that of cuttings cultured at 0 units. The root growth of rooted cuttings cultured at 0.25 units was inhibited in the nursery period. In the nursery period, the relative growth rate (RGR) of rooted cuttings cultured at 0.1 units was higher than that of cuttings cultured at 0 units. The change in RGR was related to the net assimilation rate.
This study was carried out in order to improve the cut flower production of Eustoma grandiflorum for shipment in late autumn and early spring. In this study, the effect of low-temperature treatment of imbibed seeds for cultivars with different rosette characteristics was investigated. Moreover, the effect of the day and night temperatures after the low-temperature treatment of the imbibed seeds on the growth of flowers was investigated. The experiments were conducted using two cultivars with different rosette characteristics. The bolting rate, flower budding rate, and flowering rate were increased by low-temperature treatment of the imbibed seeds regardless of the rosette characteristics. After low-temperature treatment of the imbibed seeds, seedlings of the two cultivars were raised at different night temperatures (22, 25, 28, and 31°C). With night temperatures of 28 and 31°C, the bolting and flowering rates decreased, regardless of the rosette characteristics, whereas at 22 and 25°C, the bolting rate, flower budding rate, and flowering rate were higher. For night temperatures in the range 22～31°C, the growth and length of the cut were better at lower rather than higher temperatures. Growth at different day temperatures (30 and 40°C) after the low-temperature treatment had no affect on the bolting, flower budding, or flowering rates. However, growth was more favorably promoted with a day temperature of 30°C compared with 40°C.
We aimed to obtain large-sized Japanese bunching onion (Allium fistulosum L.) for August harvesting in cold regions, which were cultivated using seedlings grown in chain paper pots maintained in an unheated plastic house. For this, we investigated the effects of nitrogen application and the number of seedlings per cell in the chain paper pots on the growth, nitrogen uptake, and yield of Japanese bunching onion. Seedlings of Japanese bunching onion grown in chain paper pots were transplanted in a field, and subjected to three nitrogen application treatments: control (2.9 kg・a–1; the standard application rate of nitrogen fertilizer in Akita Prefecture), heavy (3.5 kg・a–1; 20% greater than the control), and light (2.3 kg・a–1; 20% less than the control). The plant growth (number of emergent leaves, shoot weight, and leaf sheath diameter) under the heavy treatment was temporarily and slightly superior to both the control and light treatments during the middle-growth stage. However, the differences in plant growth among the treatments were not apparent by the harvest time. Hence, because there was no significant difference in yield among the treatments, we considered that the amount of nitrogen supplied under the light treatment was sufficient for plant growth. Different numbers of seedlings per cell (1, 2, and alternating 1 and 2 [1.5] seedlings) in chain paper pots resulted in differences in growth after planting and yield. With an increase in the number of seedlings per cell (1, 1.5, and 2 seedlings), we noted the increased inhibition of growth after planting, a decrease in the amount of nitrogen uptake per plant, and decrease in the fresh weight of shoots per plant. In contrast, the yield per area increased, because of an increase in the number of plants. The shoot weight was negatively correlated with the planting rate (plants・m–2), and positively correlated with the ground area covered by plants (cm2/plant). Thus, we observed a quadratic relation between the shoot weight and planting rate, and a linear relation between the shoot weight and ground area covered by plants.
We investigated the effect of time-dependent temperature management conducted every other day (TTMD) on the growth and berry quality of ‘Delaware’ grapes under forcing culture from January to May in order to reduce fuel consumption. This method involved lowering the standard temperature setting for forcing (control) by 5°C on alternate days. Grapevines that were grown under TTMD at night exhibited no significant differences in development (veraison, maturity), leaf color, berry growth, or berry quality compared with the control. However, fuel oil consumption was reduced by 8%. Grapevines that were grown under TTMD during the day showed no difference in the developmental period of berries or leaf color compared with the control. However, they showed lower levels of berry growth than the control from 14 days after the TTMD treatment to maturity; furthermore, they showed lower cluster and berry weights than the control. Therefore, it was concluded that TTMD is a suitable option for viticulturists if used at night from the time of berry set until the end of forcing.
We evaluated the water status of peach, grape, Japanese pear, and satsuma mandarin trees using a ‘water-stress indicator sheet’. This sheet indicates the water status of a sample by changing color (from blue to light pink); this is caused by a reaction between the sheet and water evaporating from the leaf onto which it is pressed. Decreases in the evaporation rates of grapes, peaches, and Japanese pear under water-stress conditions can be estimated using the time required for the indicator sheet to change color. This color change occurs in 100–110 s when in contact with the leaves of non-water-stressed plants, but when the plant is under sufficient water stress to reduce the evaporation rate by half, the change in color takes 200 s. In satsuma mandarin, it takes 130 and 230 s, respectively. Thus, the time elapsing between initial contact and the change in sheet color can function as a measure of the water status. However, when taking measurements for practical use, it is necessary to maintain conditions such as solar irradiance at a constant level.
The effect of irradiation with far-red (FR) light at the end of the day (EOD) on the yield and trait of plants in the family Brassicaceae was investigated. When plants were exposed to FR light under weak irradiation (34.33 or 13.44 mW・m–2) by EOD treatment, the total leaf weight and leaf area tended to increase more than in plants without treatment and under strong irradiation (96.04 or 56.70 mW・m–2). They were cultivated in winter, midsummer, and the period between winter and midsummer in Okinawa, with a sub-tropical climate, and then compared regarding the difference in each growth between the cultivated periods. In shimana, EOD-FR treatment promoted bolting. It was significantly promoted under strong irradiation compared with weak irradiation. However, there was no bolting except in shimana. Also, in shimana and bok choy receiving strong irradiation and EOD-FR treatment, stem elongation was promoted by more than 8 times and 2 times, respectively, on comparison with plants without treatment.
Night break (NB) is an effective method to depress flower induction in short-day plants. It has been suggested that red (R) light is more effective than light containing R and far-red (FR) light on the depression of flower induction. This study revealed the effect of the NB duration with R and FR light on the depression of flower induction using two genotype of chrysanthemum (summer-to-autumn flowering type ‘Iwano-Hakusen’, and autumn-flowering type ‘Jimba’). When the duration of NB was short, R light was more effective than R+FR light, and a reversible response to R-FR light was also observed. On the other hand, R+FR was more effective when more than 2-hour NB was applied for ‘Iwano-Hakusen’, and more than 45-min NB with R or R+FR showed the same effect in ‘Jimba’. The results indicate that the effect of NB was affected by both the duration and light quality of NB. Ten-hour NB with R or R+FR was given to 92 genotypes of chrysanthemum. Only a few genotypes showed a stronger depression of flower induction by R+FR NB, suggesting that R light NB should be recommended for commercial cut chrysanthemum production.
The flower of Anthurium andraeanum L. consists of a modified leaf (spathe) that subtends a cylindrical inflorescence (spadix). One flower emerges from each leaf axil. The sequence of leaf, flower, and new leaf is maintained throughout the plant’s lifecycle. In the present study, the leaf-emergence interval (LEI) and number of days from the emergence of the subtending leaf to flower harvesting (DFH), which are important factors for determining flower productivity, were monitored for 2 years in ‘Tropical’ (A. andraeanum). Seasonal fluctuation was observed in both LEI and DFH. In addition, strong negative correlations between temperature and LEI and temperature and DFH was detected. Mathematical models explaining the fluctuation of LEI and DFH were developed using the developmental index (DVI) and developmental rate (DVR). LEI and DFH were explained with high-level accuracy by the daily average temperature alone. In addition, DVR and temperature association in both models indicated an optimal growth temperature for Anthurium above 25°C. A combined model of LEI and DFH will facilitate the prediction of the number of cut flowers that could be harvested in a given period, under changing temperature conditions. This would contribute to efficient temperature control in greenhouses for the commercial production of cut Anthurium flowers.
We investigated the effect of trunk girdling on the skin color and expression levels of anthocyanin biosynthesis-related genes in the red grape ‘Aki Queen’ (Vitis labrusca L. × V. vinifera L.). Trunk girdling at the onset of coloring in mid-July significantly accelerated anthocyanin accumulation in the berry skin during maturation in comparison with that in the control (no girdling). Using quantitative real-time PCR analysis, we showed that the expression levels of anthocyanin biosynthesis-related genes such as chalcone synthase 3 (CHS3), UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT), and anthocyanin O-methyltransferase (AOMT) were significantly increased by trunk girdling in comparison with the control, although the expression levels of CHS3, UFGT, and AOMT gradually increased from mid-July to early August in both the girdling treatment and control. The anthocyanin content was closely correlated with the expression levels of many anthocyanin biosynthesis-related genes. These findings suggest that trunk girdling at the onset of coloring improves the skin color of ‘Aki Queen’ grapes by accelerating the expression of anthocyanin biosynthesis-related genes.
The effects of the force-ripening condition on the anthocyanin accumulation and concentration of components in Japanese apricot ‘Tsuyuakane’ (Prunus salicina × Prunus mume Siebold et Zucc.) fruit were investigated. The anthocyanin concentration in the flesh (with skin) sharply increased from about 4 days after starting force-ripening in ethylene presence at 20°C. The anthocyanin concentration was higher when stored at 20 or 25°C than that when stored at 15 or 30°C. The anthocyanin composition in the fruit changed during force-ripening in ethylene presence. Red coloration of fruit brought about by force-ripening was insufficient for the fruit harvested before blushing. The anthocyanin concentration after force-ripening was lower in the fruit harvested at a commercially optimal harvest time than the fruit harvested before then. The fruit size did not influence the anthocyanin concentration for the full colored fruit with applied force-ripening. The malic acid concentration increased with fruit maturation regardless of applying or not applying force-ripening. The polyphenol concentration increased by force-ripening. In conclusion, the anthocyanin concentration in force-ripened ‘Tsuyuakane’ fruit is influenced by the harvest time and storage temperature. Fruit should be harvested when 30～50% red-colored and force-ripened for about four days at 20°C in an atmosphere including ethylene gas in order to efficiently increase red-coloring and the anthocyanin concentration.
Ornamental values of cut tulip (Tulipa gesneriana L.) flowers are reduced by elongation of the flower stalks and leaf yellowing. The effect of pretreatments with 2-chloroethylphosphonic acid (CEPA), 6-benzylaminopurine (BA), and gibberellic acid (GA3) at various concentrations on the vase life of cut ‘Christmas Dream’ flowers was investigated. Pretreatments with CEPA at 25, 50, and 100 mg・L–1 significantly suppressed flower stalk elongation, but shortened the flower longevity by 2 days. Pretreatments with BA at 5, 25, and 125 mg・L–1 suppressed leaf yellowing, but pretreatment with GA3 suppressed leaf yellowing only slightly. Flower longevity was not affected by pretreatments with BA or GA3. A combined pretreatment with 50 mg・L–1 CEPA and 25 mg・L–1 BA suppressed flower stalk elongation and leaf yellowing in cut ‘Christmas Dream’ flowers. Similar results were obtained from 7 cultivars of cut flowers. These results indicate that combined pretreatment with CEPA and BA is effective for suppressing flower stalk elongation and leaf yellowing of cut tulip flowers.