Lemonade (Citrus sp.) is citrus fruits introduced from New Zealand that is cultivated in the Izu region of Shizuoka Prefecture. Using a gas chromatograph mass spectrometer (GC-MS), we measured the volatile components in the juice of lemonade, and the compositon of volatile components was compared with the juice of ‘Eureka’ lemon and ‘Trovita’ orange. We detected 34 volatile components in the juice of lemonade. Among them, 13 volatile components were not identified in ‘Eureka’ lemon or ‘Trovita’ orange, and peak areas of 19 volatile components were larger than in ‘Eureka’ lemon and ‘Trovita’ orange. The results of a sensory test involving ten panelists indicated that the juice of lemonade had a more pungent flavor than that of ‘Eureka’ lemon.
Global warming is making it difficult to achieve the chilling requirement for the completion of endodormancy in protected peach cultivation. To stabilize peach production in the face of warming winters, we examined the use of rootstock low-chilling ‘Okinawa’ and endodormancy-breaking treatments. In pot culture, ‘Hikawahakuhou’ on ‘Okinawa’ rooted and flowered earlier than ‘Hikawahakuhou’ on ‘Ohatsumomo’. Therefore, it was suggested that rootstock low-chilling ‘Okinawa’ influences the flowering of ‘Hikawahakuhou’. In field culture, ‘Hikawahakuhou’ on ‘Okinawa’ led to commercial fruit quality and growth. In the field with ‘Hikawahakuhou’ on ‘Okinawa’, the application of either of two endodormancy-breaking treatments, hydrogen cyanamide sprayed after 400 to 600 chilling hours or nitrogen metabolism solution sprayed after 600 to 800 chilling hours, advanced both flowering and harvesting dates. Under continued global warming, the use of ‘Okinawa’ as a rootstock and endodormancy-breaking treatments will enable continued production of peach.
The number of leaves on an onion plant, which is an important element of the yield, is related to the bulb diameter and weight. In order to estimate the number of leaves of an onion plant based on the accumulated temperature, we compared several calculation methods. The fitness of the estimation formula for a specific calculation method was verified by examining different variables: sowing date, cropping type, and method of phosphoric acid fertilization (broadcast or locally applied). As a result, the accuracy of the estimation method using the daily average temperature was lower than the triangle method and the average temperature method with a base temperature of 3.5°C or 5.0°C. In addition, when the base temperature to calculate the effective temperature was set for the accumulated temperature method or triangle method, a base temperature of 5.0°C was more accurate than that of 3.5°C. Therefore, our results indicate that the formula of the average temperature method with the base temperature set to 5.0°C is highly correlated with the effective temperature and number of leaves, and the prediction estimation error is small. In different cropping types, the average temperature method with a base temperature of 5.0°C was the most accurate. Based on our results, the estimation formula with the highest estimation accuracy is the average temperature method with a base temperature of 5.0°C. However, further examination is required involving other varieties and regions, but the coefficient of the estimated formula suggests that onion plants develop 1.5 leaves per accumulated temperature above 5.0°C of 100°C・day.
In Easter Lily (Lilium longiflorum Thunb.)’s bulb production, reducing the labor required for budding work is necessary. Easter lily causes blasting when susceptibility to ethylene increases, and we aimed to develop an effective disbuddding technique in bulb production utilizing this characteristic. As a result, especially for 3 weeks after budding, it was easy to promote blasting with shading. Most varieties had a higher ethylene sensitivity from 1 week before budding until 2 to 3 weeks after budding. About 1 week before flower budding with high ethylene sensitivity, blasting was induced efficiently by treatment with ethephon or a surfactant to the growing point, suggesting that these treatments can be applied to disbudding in bulb production. In addition, there is a difference among varieties in ethylene susceptibility, and ‘Purehorn’ is considered to be a low-ethylene-susceptible variety. However, internode elongation was suppressed along with flower bud development, and there is concern that bulb enlargement may also be suppressed. Therefore, further study is necessary for the practical application of labor-saving disbudding technology.
In the cultivation of strawberry plants using an elevated bench system, we studied methods of raising plantlets with the aim of reducing labor time and nursery facility requirements. First, the direct-planting of strawberry cuttings produced in a plantlet production facility was investigated. The rate of root establishment was increased under cold treatment and the total yield was similar to that obtained in a conventional nursery. Second, runner plantlets produced from fruit-harvested plants were planted directly in the bench. This achieved a similar level of productivity compared with conventional nursery runner plantlets and runner plantlets from a plantlet-producting facility. However, it was not possible to avoid missing plantlets using these methods. Therefore, the direct-planting of runner plantlets connected to fruit-harvested plants was tested, and this method increased the rate of root establishment and resulted in a similar yield to conventional nursery methods. These results indicated that the direct-planting of such runner plantlets could reduce labor time and nursery facility requirements.
To characterize factors determining the varietal differences in the fruit size of Japanese plum (Prunus salicina Lindl.), we investigated the relationships among fruit weight, flesh thickness, cell numbers, and radial cell lengths of flesh at the ripening time in 6 cultivars for 2 years. The correlation coefficient between the fruit weight and flesh thickness was higher than 0.9, and the cultivar with large fruits had thicker flesh. There was a varietal difference in cell numbers of flesh, and the cultivar with large fruits had more cells. On the other hand, differences in radial cell lengths of flesh among the cultivars were not clear. In the investigation of correlation coefficients among measurement items, although a correlation was noted between the thickness and radial cell lengths in flesh, the correlation coefficient was low, at about 0.3 to 0.5. Conversely, the correlation coefficient between the thickness and cell numbers in flesh was high, over 0.9. The results revealed that the differences in fruit size among Japanese plum cultivars were markedly influenced by the cell number rather than radial cell length.
Using an artificial light source, the effect of natural twilight irradiance intensity on the photoperiodic responses of autumn-flowering chrysanthemum was examined. When exposed to light from a red fluorescent lamp, four cultivars of chrysanthemum exhibited a higher inhibitory effect on flowering in the morning than in the evening under the same irradiance. When exposed to light from a red (R) light-emitting diode (LED) lamp, the threshold irradiance of the chrysanthemum cultivar ‘Jimba’ was less than 10 mW・m–2 in the morning and approximately 70 mW・m–2 in the evening. The effects of R and R + far red (FR) light were also investigated in ‘Jimba’. There was a difference in the morning treatment; however, there was no difference in the evening treatment. It was considered that the FR light did not influence the threshold of R light. In ‘Jimba’, the threshold irradiance for the photoperiodic flowering response increased with the age of the plant. The natural twilight irradiance was measured for 102 d in Ibusuki City. The results revealed that the sunrise and sunset light intensities changed for about 20 min each morning and evening owing to the influence of the terrain and weather. Using the threshold irradiance for the photoperiodic response with R light, we estimated the illuminance in the morning and evening in the dark period of ‘Jimba’. The results revealed that less than 8 lx in the morning and 54 lx in the evening are the light and dark thresholds for photoperiodic flowering. However, this estimate may vary depending on the weather factors and test environment conditions (place, cropping type, and growing environment).
Incandescent light bulbs are widely used in light culture to promote flowering in long-day cut flowers. However, alternative energy-efficient light sources need to be developed. This study evaluated the flowering-promoting effect of two bulb-type three-color LEDs on two Gypsophila paniculata cultivars. The LEDs are equipped with far red, red, and blue colors and can be attached to the socket of an incandescent light bulb. Regarding the number of days to flower budding, LEDs exerted a flowering-promoting effect equivalent to that of incandescent light bulbs. However, incandescent light bulbs were more effective compared with LEDs in terms of the number of days to flowering in one of the two cultivars and number of leaves at flowering in both cultivars. The LED use resulted in an equal or superior fresh weight, stem length, and number of inflorescence units as the cut flower quality than those achieved with incandescent light bulbs. Although there may be an influence of light quality other than the three colors on flowering, the potential of bulb-type three-color mixed LEDs with a marked energy-saving effect was shown for the promotion of flowering.
To elucidate the cause of failure of cutting of chrysanthemum following hot water treatment, we investigated the occurrence of the disorder and action of light after hot water treatment using autumn flowering ‘Jimba’. After hot water treatment, the damage became greater as the amount of light increased, and it was shown that light is involved in the occurrence of the disorder. In addition, it was suggested that the disorder was alleviated by placing the cutting of chrysanthemum for darkening for 48 hours or more after hot water treatment, and it recovered from damage due to light irradiation. Furthermore, on examining the maximal quantum efficiency (FV/FM) measurement values of chrysanthemum leaves after treatment with 48°C hot water for 1 minute, a decrease in the FV/FM value occurred, and after 72 hours at 20°C under darkening conditions, FV/FM value recovery was confirmed. Considering these facts, although leaf burn due to light inhibition occurred immediately after hot water treatment, it was suggested that photosynthesis recovered by darkening for 2 to 3 days, and it was effective as a measure to avoid the occurrence of the disorder. In addition, treatment with ascorbic acid added to hot water reduced the occurrence of the disorder. This indicates that increasing the active oxygen scavenging ability of chrysanthemum is effective as a method to avoid the occurrence of the disorder.
Ultraviolet-B (UV-B; wavelength, 280–315 nm) is known to induce resistance against various plant diseases. In this study, irradiation of UV-B was examined to determine optimal conditions in cucumber and tomato seedlings using a UV-B fluorescent lamp. Powdery mildew was suppressed by daily 2-hour irradiation of UV-B at 50 and 100 mW・m–2 in both species, but visible leaf injury occurred on UV-B irradiation at 100 mW・m–2. Daily 1-hour UV-B irradiation had insufficient effects; on the other hand, 2 or 3-hour treatment had the same effects as conventional chemical protection. As a result, optimal conditions of UV-B irradiation were considered to be 50 mW・m–2 for 2 hours daily in cucumber and tomato seedlings, and UV-B irradiation is considered to be an alternative method for practical protection from powdery mildew.
Strawberries are a labor-intensive agricultural product. Packaging strawberries, in particular, is time-consuming, and is a major burden on producers. In recent years, packaging centers in charge of packing operations for producers have emerged in major strawberry-producing regions; however, they are not fully capable of meeting producers’ demands. We developed a prototype strawberry fruit-class sorting apparatus that can measure the amount and value of strawberry to fix the payment from each strawberry producer at the time of shipment acceptance, through the weighing of boxed strawberries, image capture, and image processing. This prototype yielded an accuracy equal to or higher than that achieved by the manual classification of strawberries by humans; moreover, the introduction of this prototype was determined to shorten the time required by packaging workers by about 14 min per strawberry producer. These results can thus improve the operating efficiency of packaging centers. However, image processing of strawberries was found to be influenced by the background color, suggesting the need to consider the color of the cushioning material that is used to box strawberries.
Poor coloration of colored grapes grown in warm regions is a frequent problem. The application of abscisic acid (ABA) to grapes can increase the content of anthocyanins in their skins. To improve bunch color, a new plant bioregulator, S-ABA, has been approved in some countries. As no protocols have yet been established for its commercial use in Japan, we evaluated the effects of spray treatment with a liquid formulation containing S-ABA (KS-102) on the fruit quality characteristics of ‘Pione’ grapes in open field culture for 4 years and in rain-protected culture for 2 years. A spray of 500 ppm S-ABA solution to bunches at the onset of pigmentation promoted skin coloration at harvest in both experiments. The soluble solid content was not affected, but the titratable acidity was reduced, increasing the sugar-acid ratio. Treatment did not affect other fruit qualities. Coloration became stronger under lower temperatures between treatment and harvest than under higher temperatures. The improved coloration became apparent in 2 weeks and was maintained until harvest.