In Akita Prefecture, traditional eggplant cultivars such as ‘Aradokoro’, ‘Sekiguchi’, ‘Senboku Maru’, and ‘Tomizawa’ are cultivated, but the relationship and history of these cultivars with other traditional Japanese cultivars are not known. Cluster and population structure analyses of 46 traditional Japanese eggplant cultivars, including these four cultivars, and three closely-related species were used to elucidate the genetic relationships and introduction pathways. As a result, we could not identify any cultivars genetically related to cultivars in Akita. However, the population structure of the cultivars in Akita revealed that their ancestors may have arisen from varieties west of Kinki and Kyushu and been introduced to Akita after genetic exchange with cultivars from Niigata and Osaka. Traditional cultivars are not only a potential genetic resource, but also an asset that has been passed down through the history and culture of the region, so it is important to pass them on to the next generation.
In purplish brown-colored Chinese lantern (Physalis alkekengi L. var. franchetii Makino), investigation of coloration of the persistent calyx and induction of mutants obtained by synchrotron-light irradiation was carried out. As results of the investigation of pigments in the persistent calyxes by HPLC, the calyxes contained petunidin and malvidin glycosides, and the anthocyanins caused purplish brown coloration. The calyx-color mutants were obtained by synchrotron-light irradiation treatments, and the mutants included those showing increased or decreased purplish brown colored area in the persistent calyxes as compared with the control. The highest percentage of persistent calyx-color mutants was recorded with the 10-Gy irradiation treatment. Furthermore, several mutants with horticulturally desirable traits, such as dwarfism, increased numbers of persistent calyxes per plant, and small persistent calyxes, were also obtained. These results suggest that synchrotron-light irradiation can be a very effective tool for the breeding of Chinese lantern.
For the purposes of utilizating genetic resources and conserving endangered endemic Japanese species, interspecific hybrids between Veronica ornata Monjuschko (Plantaginaceae) and V. ogurae (T. Yamaz.) Albach in Shimane Prefecture were created. In the reciprocal crossings, hybrid seeds were obtained from only the cross involving V. ornata as the seed parent and V. ogurae as the pollen parent. The expected number of obtained seeds on interspecific crossing was 0.5 per flower. The hybridity of the obtained seedlings was confirmed as the original bands were inherited from both parents in the SRAP method. In the characterization of the parents and their 92 hybrids in the flowering season, the leaf size and amount of pubescence in the stems and leaves of the hybrids were intermediate between the parents, and the spike length and flowering period of the hybrids were longer than those of the parents. The inheritance of these ornamental characteristics was supported by the results of principal component analysis. The results of this study suggest the possibility of being able to develop superior cultivars by crossing and selection focusing on ornamentally important characteristics.
Based on the relationship between the branch diameter and leaf weight, the authors set the fruit-thinning criterion as the branch diameter and evaluated the effects on productivity and fruit characteristics in the citrus cultivar ‘Harumi’. The relationship between the branch diameter (X) and leaf weight (Y) was Y = AXB for on-year, standard, and off-year phases, respectively. The branch diameter was calculated corresponding to 100 leaves and set as the fruit-thinning criterion in each tree phase (one fruit set per branch of 0.8 cm in diameter). Adopting this criterion in the three phases resulted in fruit-thinning rates ranging from 91.4 to 57.2% in accordance with the fruit load. There was no difference in the harvested fruit number per canopy volume among phases. The percentage of valuable fruit size between 180 and 250 g was kept at more than 50% in the standard phase, and its value in the off-year phase was improved with the modified fruit-thinning criterion. Flower number per node in the following season showed successive fruit production. Thus, applying the fruit-thinning criterion as the branch diameter corresponding to tree phases facilitated control of the fruit number leading to the production of a high rate of valuable ‘Harumi’ citrus fruits.
Effects of sheet mulching on auraptene (AUR) and polymethoxyflavone (PMF) contents in the peel of mid-late maturing citrus ‘Kawachibankan’ (Citrus kawachiensis hort. ex. Y. Tanaka) fruit were investigated. Six vigorous nine-year-old trees were used, and three of them were mulched with a permeable plastic sheet on the ground from September to January. The results showed that no significant difference was observed in fruit development between mulch and control. Mulching cultivation caused higher rind color a* and b* values than in the control. Soluble solid content in the juice of mulched fruit markedly increased after treatment, which retained higher levels even in May. The juice citric acid content in treated fruit was also higher than in untreated fruit until the end of March, although no significant difference was observed thereafter. Peel AUR in mulched fruit showed a significantly higher content in December and April compared with the control. Peel AUR in whole fruit had the highest content in April. The juice AUR content in mulched fruit was also higher than in the control in April and June. No difference in the PMF content in peel was found between the treatment and control. Mulching cultivation caused rapid increases in total sugar, glucose, and fructose contents in the peel in October. These results indicate that peel AUR in whole fruit had the highest content in April and May, whereas mulching cultivation is effective to increase the amount of AUR in the peel and juice, suggesting that these were caused by drought stress and cold temperature.
To achieve the stable supply of spinach for processing use, scheduled harvest based on growth prediction is effective. In this study, we investigated the effect of temperature and solar radiation on the dry matter production of spinach, and quantified the relationship. The leaf area index (LAI) was fitted with a logistic curve with integrated temperature as the explanatory variable. The fraction of radiation intercepted by the foliage was approximated by 1-exp(–0.69 × LAI) when LAI was below 3.26, and was constant at 0.89 in the higher LAI range. Average radiation-use efficiency was 0.98 g·MJ–1, which was approximated by a logarithmic function with the mean temperature of the previous three days as the explanatory variable. The model constructed based on these relationships was validated using the growth data obtained in a different year. As a result, the logistic relationship between the integrated temperature and LAI was applicable for three data-sets obtained from cultivation tests with different planting dates. For a data-set in which early growth was retarded, minor adjustment of the integrated temperature improved the fit of the model. The correlation coefficient between estimated and observed dry matter production based on the modified model was 0.98.
We examined the effects of LED irradiation and heating temperature on flowering and growth of pot carnation (Dianthus caryophyllus L.). Under heating at 12°C and overnight irradiation with red LED (wavelength 620 to 630 nm), varieties of ‘Chantilly’, ‘Claire’, and ‘Granrouge’ did not grow taller than those with far-red LED (730 to 740 nm), but did show accelerated flowering compared with those with no LED irradiation. Especially in ‘Chantilly’, flowering of the primary flower was observed earlier when the day length was elongated to 24 hours by red LED irradiation compared with 16 hours. In the above three varieties, when the heating temperature (9 and 12°C) and overnight irradiation with red LED were combined, overnight irradiation with red LED accelerated flowering regardless of the heating temperature. The number of lateral flower buds and flower buds in the upper node of the secondary branch were also increased by overnight irradiation with red LED. Accelerated flowering caused by overnight irradiation with red LED was noted even under heating at 9°C in the three varieties. In all 11 varieties (two varieties above excluding ‘Granrouge’ and nine varieties including ‘Cheerfulred’) tested, the combination of overnight irradiation with red LED and heating at 9°C promoted flowering similarly to conventional cultivation (no LED irradiation and heating at 12°C).
We investigated the effects of shading, UV-rays, and temperature on changes in the flower color of the panicled hydrangea (Hydrangea paniculata Sieb.et Zucc.) ‘Limelight’. The sepals were white (fresh colored) during the early stage of flowering, but turned red (antique colored) during the late stage. This was accompanied by a gradual decrease in the L* value. The a* value was 13.4 in the control during the late flowering stage, and it was significantly lowered by shading, reaching 8.6 and –2.6 under 70 and 90% shading, respectively. After flowering, the greater the percentage of net-based shading, the slower the change in sepal color from white to red and lighter the final color. The use of UV-cut film to achieve 98.4% shading resulted in the sepal color slowly changing to pale red. The L* value remained significantly higher, and the a* and 530-nm absorbance values of sepal extracts significantly decreased. The change in the sepal color was also affected by night temperatures, ranging from 5 to 20°C, and it was promoted the most at 15°C (a* = 17.8). Thus, illuminance (>15,000 and <114,000 lx) and ultraviolet rays (>0.300 and <2.524 mW・cm–2) may be required for sepals to turn red, and the optimum night temperature was approximately 15°C. However, sepals were greenish even at the end of flowering under 90% shading, suggesting that it is possible to produce greenish panicled hydrangea.
For marine transport bound for North America of three astringent-type persimmons, ‘Tonewase’, ‘Hirateneashi’, and ‘Nakataniwase’, optimum temperature and efficacy of 1-MCP treatment were studied for fruit transported in carton boxes coated with a water-impervious material. In addition, the effect of MA packaging was investigated in ‘Tonewase’ fruit. On the whole, a lower temperature ranging from 25 to 0°C resulted in longer control of fruit softening in ‘Tonewase’ fruit; however, fruit stored at 5 and 10°C showed symptoms of chilling injury. The benefit of 1-MCP treatment at harvest persisted for up to two weeks at 25 and 20°C, three weeks at 15 and 10°C, four weeks at 5°C, and 1 week at 25°C following one-month storage at 0°C. MA packaging using polyethylene film had significant inhibitory effects on fruit softening at low temperature, while its additive effects with 1-MCP treatment were limited. In ‘Nakataniwase’, fruit softening progressed immediately after transfer to 25°C following one-month storage at 0°C, even in fruit treated with 1-MCP. In ‘Hiratanenashi’, fruit stored at 0°C for one month did not soften for up to 10 days after transfer to 25°C, regardless of 1-MCP treatment. These results suggest that the optimum temperature for marine transport bound for North America, possibly taking around one month, is 0°C. In addition, 1-MCP treatment at harvest is not sufficient to retain commercial fruit quality during shelf life after marine transport in ‘Nakataniwase’ fruit. In ‘Tonewase’, the combination of marine transport at 0°C and 1-MCP treatment at harvest or MA packaging can effectively inhibit softening during shelf life following marine transport. In ‘Hiratanenashi’ fruit held at 0°C, 1-MCP treatment is not necessary to maintain fruit quality for up to 10 days during shelf life following marine transport.
To extend the shipping period of blueberry fruits, we compared the storability of the new interspecific hybrid blueberry HoSp-S65G-13, which is suitable for cluster harvesting, with that of existing cultivars. Moreover, we investigated the effects of different harvesting methods (individual and cluster harvesting) on storability and fruit quality. Storability did not differ significantly among HoSp-S65G-13, ‘Chandler’, and ‘Tifblue’; however, weight loss was significantly lower in cluster-harvested fruits than in individually harvested fruits after two weeks of storage. The Brix value and acidity showed no significant difference between harvesting methods; however, cluster harvesting suppressed fruit decay during storage. Sensory testing showed that after five months of storage, cluster-harvested fruits were equivalent to imported fresh fruits, whereas individually harvested fruits were rated significantly lower than imported fresh fruits. Thus, cluster harvesting of blueberries suppressed weight loss and fruit decay, suggesting that this harvesting method may help extend the storage period of blueberries.
No cabbage-sorting machine exists that distinguishes fresh cabbages with 2–3 outer leaves and processes cabbages without outer leaves. We developed a cabbage-sorting system based on machine learning using a convolutional neural network (CNN) approach to support people with disabilities. We also fabricated a cabbage-sorting device using a web camera, load cell, and microcomputer. We created a “fine-tuned” CNN by modifying the VGG16 architecture. For the fine-tuned CNN, the discrimination accuracy and all other evaluation metrics were high. The time required to complete the operation by the cabbage-sorting device was 5.8 seconds for the fine-tuned CNN. These evaluations indicate that the cabbage discrimination program should incorporate the fine-tuned CNN. This cabbage discrimination system can be used to assist beginners and people with disabilities, which could help reduce the labor shortage.
An automatic shading system that can control the opening and closing of shading material according to the intensity of solar radiation was devised in order to minimize the decrease in growth and yield of tomato in summer-autumn harvesting cultivation due to high temperature and excessive solar radiation in summer. The control method was established according to the photosynthetic properties of tomato, and the effect of application of the system on its growth and yield was assessed. Based on the measurement results of the photosynthetic rate of individual leaves and the light environment of the plant community, it was found that the upper limit of the appropriate range of the setting is PPFD 1200 ~ 1600. It was also noted that the lower limit was 670 μmol・m–2・s–1 or more, which is less than the upper limit multiplied by the light transmittance of the shading material. Based on the measurement results of the photosynthetic rate and response time of stomatal conductance associated with light intensity, the control interval at which the solar radiation sensor senses the light intensity and opens and closes the shading material should be as short as possible within the range not less than the time required for the opening and closing of the shading material. Furthermore, it was shown that the yield of marketable fruits increased and fruit cracking was reduced without a decrease in the stem diameter or succulent growth by shading based on the control method in summer-autumn harvesting tomato cultivation.
A new red-fleshed apple cultivar, ‘HFF33’, which has superior taste and storability compared with ‘Kurenainoyume,’ was bred at Hirosaki University. Genotype analysis using SSR markers revealed that ‘HFF33’ could be obtained from a combination of ‘Toko’ × “Red-fleshed apple strain Parent A”. The fruit has a conic shape, the peel develops a bright striped blush similar to ‘Senshu,’ and the flesh develops a crimson color on maturation. The tree had a branched shape, and the shoot growth was not so strong like ‘Orin’, although the branches were easily broken because of their thickness. At our experimental site, the suitable harvest time for this cultivar was the middle of November, and the fruit weighs 400 g, has a 13.4% soluble solid content, and around 0.6% titratable acidity. Fruit-bagging treatment completely prevented the development of cork spot-like physiological disorders and improved the skin blush: the color became brighter, and the stripe developed more distinctly than in non-bagged fruit. ‘HFF33’ exhibited long storability and could be stored under cold conditions for 180 days after harvest. Moreover, 1-MCP treatment was effective in preventing the loss of firmness. We registered ‘HFF33’ commercially with the trademark MIKU. Using this trademark, we will ensure quality control and establish the brand value.