There is increasing interest in fruits of bramble crops (Rubus spp.) because of the possible benefical health effects associated with their phenolic content. Almost all cultivars are from Europe and the United States, although there are many wild Rubus species native to Japan. In order to obtain basic knowledge for the horticultural application of those wild species, we collected and evaluated some wild species native to Kyusyu Island as genetic resources. All raspberry cultivars were diploid, but almost all wild species were diploid with a different genome size, except for a few hexaploids. The aggregate fruit weights of wild species were not smaller than cultivars except for Rubus lambertianus Seringe. The ripening fruits of some wild species, R. crataegifolius Bubge., R. trifidus Thunb., and R. palmatus Thunb., were higher than the fruits of raspberry cultivars regarding total sugar contents and lower in total organic acid contents. The fruits of R. crataegifolius Bubge., R. palmatus Thunb., and R. lambertianus Seringe also showed a higher total polyphenol content and antioxidant activity than the cultivars. Some wild species native to Japan may be useful as breeding material to establish some new cultivars adaptable to Japan with high quality and functionality.
Some Hydrangea macrophylla cultivars and interspecific H. macrophylla × H. serrata hybrids are self-incompatible, making it difficult to breed them for recessive characters. To overcome self-incompatibility, pollinating at different flowering stages and hot-water treatments of the inflorescences were conducted using ‘03NL3’, an interspecific H. macrophylla × H. serrata hybrid. Pollen tube growth was examined by fluorescence microscopy. At 3 days after pollination, the pollen tubes in flowers pollinated at 2 and 4 days after anthesis failed to reach the ovules. However, the pollen tubes were longer in styles pollinated 1 day before anthesis, and some had reached the ovules. For hot-water treatments, inflorescences were immersed in hot water (45°C) for 1–5 min before self-pollination. The 3- to 4-min treatments promoted pollen tube growth. Selfed ovules were obtained by bud pollination, hot-water treatment (45°C water for 4 min) of the inflorescences, and the combination of both treatments. Fertilized ovules were cultured in 1/2 MS medium and then grown in a greenhouse. At least half of these plants flowered within 2 years after self-pollination. The combination of bud pollination and hot-water treatment yielded the highest rate of selfed individuals.
In order to breed early flowering and highly productive cultivars with long vase life or disease resistance in the carnation (Dianthus caryophyllus L.), genetic variation and photoperiod responses in earliness of flowering were studied in a phytotron experiment using recent standard-type carnation cultivars, interspecific hybrids between the carnation and D. superbus var. longicalycinus and their backcrossing progenies. Our results indicate that there was a large genetic variability in flowering times and photoperiod responses among the tested 11 materials. In ‘Mizuki’ and ‘Rachel’, which were two of the earliest flowering cultivars in the preliminary test using 21 cultivars, the mean number of days to flowering was less than 100 days for long days (LD) treatment, and all tested plants flowered within the experimental period (a 169-day period) for short days (SD) treatment. However, ‘Hitomi’, ‘Karen Rouge’, and ‘Miracle Rouge’ did not flower in all their tested plants within the experimental period for SD treatment. Our results showed that interspecific hybrids between the carnation and D. superbus var. longicalycinus and their backcrossing progenies are facultative long-day plants, which means that they flower faster with LD than with SD treatment. Although the crosses using ‘Rachel’ as the seed parent produced no seed, the crosses using ‘Mizuki’ as the seed parent showed high-cross compatibility and produced many progenies. The F1 seedlings using ‘Mizuki’ as the seed parent showed a very early flowering habit, compared to the F1 seedlings using ‘Le France’ as the seed parent. These results suggest that earliness of flowering in ‘Mizuki’ is heritable.
Reproductive characteristics of the tetraploid plants of Actinidia collected in a warm Pacific region on Kyushu Island, Japan, were investigated and compared with those of diploid A. rufa, which grows in the same area. Morphological characteristics of tetraploid plants, such as skin color and lenticel of fruit, were similar to those of A. rufa; however, the number of petals, color and hair of calyx, and shape of fruit were distinguished from A. rufa. All the tetraploid plants bore only morphologically hermaphroditic flowers. Pollens collected from these flowers germinated at a high rate of 40–61%. By self-pollination, the flowers of the tetraploid plant set fruit over 97%. The seeds obtained by self-pollination germinated at a high rate of 81%. By the cross between the tetraploid plant and tetraploid cultivars of A. chinensis, viable seeds were obtained. The seeds germinated at 65–92%. These results showed that tetraploid Actinidia plants are functionally hermaphroditic and self-fruitful, implying a potential as breeding materials.
To produce a laborsaving variety with a short-internode-trait in tomato, the early selection method for the short-internode-trait was examined using breeding material with parthenocarpy. ‘Rinka 409’ was selected as a promising material with a short-internode-trait. The efficiency of the newly developed early selection method for the short-internode-trait was evaluated in S1 and S2 progeny of ‘Rinka 409’. A strong positive correlation was observed in the plant height in the early growth stage and length from the ground to the fifth fruit truss at the end of cultivation. According to this finding, individuals with a short length from the ground to the fifth fruit truss at the end of cultivation can be selected at an early growth stage by selecting those with a short height in this stage. The height of S2 progeny of ‘Rinka 409’ selected by the method in S1 was significantly shorter than that of F1 or S1 individuals. Heredity of the short-internode-trait using the early selection method was also observed in the F1 progeny between S2 individuals with a short internode and the parthenocarpic line. These results indicate that it is possible to efficiently introduce the short-internode-trait into parthenocarpic tomato using the plant height in the early growth period.
This study aimed to assess the effects of heading-back, lateral shoot pinching, culture soil, and gibberellin paste treatment on the growth of peach nursery stock for use in the tree joint training system. The main shoots of stock subjected to heading-back treatment at 100 cm above the ground were longer than those of untreated stock (controls). However, no difference in the trunk length was observed. Further, the treated stock were easy to bend and hard to break when training; thus, heading-back the treatment was considered a suitable propagation method for peach nursery stock to be used in the tree joint training system. Longer main shoots and trunks were observed in stock subjected to pinching treatment of the lateral shoot with up to 2 leaves than in those subjected to pinching treatment of the lateral shoot with up to 5 leaves. Thus, the pinching treatment with up to 2 leaves was considered a suitable raising method. Longer main shoots and trunks were observed in stock grown in Akadama compared to Masa soil. Therefore, Akadama soil was considered a suitable raising method. The main shoots and trunks of stock treated three times with gibberellin paste were longer than those of stock treated either once or twice. However, the lowest rate of fine roots was observed in stock treated three times with gibberellin paste. In contrast, the second longest main shoot and trunk of stock treated twice with gibberellin paste showed no difference in the rate of fine roots when compared with the controls. Therefore, treatment twice with gibberellin paste is considered a suitable raising method.
To reestablish agricultural production in the farmlands damaged by the Great East Japan Earthquake in the Sanriku region, we tested the effects of application of non-composted spent shiitake (Lentinula edodes) substrates (SSSs) as an organic soil conditioner. Sweet corn (Zea mays) was cultivated at Rikuzentakata as a test plant. As a result of SSSs application, chemical, physical, and biological properties of the soil were improved. Nitrogen deficiency and growth inhibition generally occur when non-composted organic matter with high C:N ratio is applied. SSSs had a high C:N ratio and were non-composted, but SSSs promoted plant growth even at early stages, suggesting that nitrogen nutrients from SSSs were immediately provided to plants without nitrogen deficiency and growth inhibition. The plants using SSSs grew slowly compared with those using chemical fertilizers; however, yields were similar. Thus, application of non-composted SSSs is an effective soil restoration treatment without decreasing yield in damaged farmlands.
The effects of short-term heating applied as a 4-h end-of-day (EOD) or end-of-night (EON) heating on the flowering of winter-cultivated spray-type carnation (Dianthus caryophyllus L.) cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ were investigated. Furthermore, the effects of a night temperature of 5 or 10°C after EOD heating were also investigated. In both cultivars, days to anthesis decreased with short-term heating treatments. Yields of cut flowers from January to March in EOD and EON heating treatments were almost equal, and higher than in the control. However, EON heating adversely affected the flower quality, resulting in a lower weight of cut flowers and decreased number of florets. When EOD heating was followed by a lower night temperature (5°C), the yield of cut flowers was equal compared with the control treatment, but the energy needed for greenhouse heating in winter was reduced. In conclusion, it was found that EOD heating was more preferable as short-term heating to promote the flowering of winter-cultivated spray-type carnation cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ while maintaining cut flower quality, and the lower night temperature after EOD heating was effective to reduce energy use in winter while maintaining the yield of cut flowers.
After greening udo (Aralia cordata Thunb.) is harvested, the rootstock is usually discarded. By growing accessory buds that were epiphytic on rootstock of ‘Toneshiro’, ‘Murasaki’ (a cultivar native to Gunma), and ‘Aichimurasaki’, we were able to harvest small spears of udo (udo no me) from each cultivar after harvesting the greening udo. The yield and number of udo no me from rootstock of ‘Toneshiro’ were 60.2 g and 12.3, those of ‘Murasaki’ were 73.0 g and 14.9, and those of ‘Aichimurasaki’ were 87.8 g and 18.3, respectively. The appearance of udo no me was similar to that of tara no me spears of the Japanese angelica tree (Aralia elata (Miq.) Seem.). The use of rootstock awakening from dormancy after harvesting greening udo in semiforced culture enabled the sprouting of accessory buds about three times for primary buds of ‘Toneshiro’ and ‘Kairyouise’, and udo no me could be produced from each cultivar. However, when rootstock was processed with gibberellin to break dormancy in forced culture, the sprouting of accessory buds on each cultivar was poor and unsuitable for udo no me production.
For efficient frost protection of fruit species, we constructed risk prediction models of frost damage for apples, Japanese pears, peaches, and cherries, using data obtained from the freezing treatment of twigs bearing flower buds. These are logistic regression models designed to estimate the occurrence of frost damage during flower bud development from the bud break stage to the post bloom stage. These models were obtained from logistic regression analysis using the freeze treatment temperatures as explanatory variables. On the basis of a likelihood ratio test, the fitness of all models was good, and judging by the identification rate, the prediction accuracy was high, except for the bud break stage model of the ‘Fuji’ apple and the calyx red stage model of the ‘Akatsuki’ peach. Nevertheless, with the exception of some of the development stage models for cherries, it became clear that the logistic curve of each model shifted to the high temperature side from the bud break stage to the post bloom stage. This phenomenon suggests that the importance of frost protection increases as the flower bud develops. Risk prediction based on the estimation of economic losses caused by frost damage is needed for effective frost protection. However, in our experiment, we did not examine damage after the post bloom stage. Therefore, in the future, we will evaluate the utility of models by examining past and future cases of frost damage caused under field conditions.
Effects of the harvest time, fruiting position, and lighting condition on the blushing and functional components of Japanese apricot ‘Tsuyuakane’ (Prunus salicina Lindl. × Prunus mume Sieb. et Zucc.) fruit were determined. The blushing index of the fruit skin tended to increase with fruit development and in the fruit on the outer side of the canopy, which tended to be higher than in fruit on the inner side when they were compared at the same harvest time. The anthocyanin content in the flesh with skin tended to increase with fruit development until the day of full ripening, and that in the fruit on the outer side of the canopy tended to be higher than in fruit on the inner side when they were compared at the same harvest time. The malic acid content was higher than the citric acid content in the flesh with skin. Both malic and citric acid contents tended to increase with fruit development until the day of full ripening, except for the citric acid content on outer side of the canopy, and, in the fruit on the outer side of the canopy, contents tended to be higher than in fruit on the inner side when they were compared at the same harvest time. The phenolic content in the flesh with skin tended to decrease with fruit development until the day of full ripening, and there was no difference between the fruit on the outer and inner sides of the canopy when they were compared at the same harvest time. The β-carotene content in the flesh with skin tended to increase with fruit development until the day of full ripening, and there was no difference between the fruit on the outer and inner sides of the canopy when they were compared at the same harvest time. Shading fruit from sunlight for about 4 weeks before harvest led to a clear decrease in surface blushing, and tended to decrease anthocyanin, malic acid, and citric acid contents. These results show that ‘Tsuyuakane’ fruit should be grown under rich sunlight to produce abundant anthocyanin and other functional components, and their content in fruit on the inner side of the canopy is poorer than in that on the outer side.
We describe the use of pulsed lighting from yellow fluorescent light emitting diodes (LEDs) designed for moth control in the cultivation of small-flowered spray-type chrysanthemums. The pulses had a 20 ms pulse width and a 80 ms dark period. The effects of the irradiance of pulsed light (0, 20, 35 and 50 mW·m−2) on the flowering and the cut flower characteristics have been investigated. No significant differences were found in the number of days to flower budding and flowering, flower formation, and on the cut flower characteristics grown using an irradiance of 20 mW·m−2. However, in some cultivars, the number of days to flowering and the cut flower length of plants exposed to 35 and 50 mW·m−2 irradiance increased significantly compared to unexposed plants.
The effects of night-break treatment at different times on flower bud initiation in chrysanthemum were investigated using ‘Jinba’ and ‘Iwanohakusen’. These two genotypes are major autumn and summer-to-autumn flowering cultivars in Japan, with different critical day lengths. The most sensitive timing of night-break treatment was not the middle of the night, but the late time zone of the night in ‘Iwanohakusen’. When the dark period started earlier on using shade materials, the timing of the maximum sensitivity to night-break treatment became earlier. The relationship between the day-length (12, 10, and 8 h) and timing of night-break treatment in the flower initiation response of the autumn chrysanthemum cultivar ‘Jinba’ was investigated. The day length was longer as the timing of maximum sensitivity to night-break treatment shifted to the late time zone of the night. The results suggest that the timing of light sensitivity in the night-break response relates to the beginning of the dark period. In ‘Jinba’, the most sensitive timing of night break appeared about 9–10 h after the beginning of the dark period. In comparison with autumn flowering and summer-to-autumn flowering chrysanthemums, summer-to-autumn flowering genotypes showed a tendency whereby the most sensitive timing of night-break treatment appeared at an earlier time from the beginning of the dark period. The results suggest the relationship between the critical day length and most sensitive time zone of the dark period.
Quantitative evaluation of the crisp texture of ‘Taishuu’ persimmon was studied based on an acoustic measurement of crispness (AMC). Measurements of the texture of ‘Taishuu’ persimmon stored for varying days after harvest suggested that the energy texture index (ETI) calculated at frequency bands from 100 to 140 Hz and above 3,200 Hz could be used to quantitatively evaluate the crispness. Measurements of the texture of ‘Kanshu’ persimmon with a different texture from that of ‘Taishuu’ persimmon revealed that there was a significant difference between ETIs of the two cultivars, especially above 4,480 Hz. These results suggest that ETIs with a frequency above 4,480 Hz can be used to quantitatively evaluate the crisp texture of ‘Taishuu’ persimmon. Furthermore, the effects of differences in harvest maturity on the persimmon texture were studied. The ETIs of ‘Taishuu’ persimmon harvested with a color score of 4.5 were lower than those harvested with a color score of 3.5, and corresponded to those of fruit harvested with a score of 3.5 and stored for 7 to 9 days. The crisp texture of ‘Taishuu’ persimmon is an important characteristic. Therefore shipment of the fruit with a color score above 4.5 may lead to a decline in the market rating of ‘Taishuu’ persimmon.