The waterlogging tolerance of Actinidia macrosperma, originating from the mid part of China, was compared with that of kiwifruit, and the potential ability of A. macrosperma to serve as waterlogging-tolerant rootstock for kiwifruit was determined. Two-year-old potted vines of own-rooted A. deliciosa ‘Hayward’, A. chinensis [FCM1], and A. macrosperma [Fuchu] were subjected to waterlogging for 14 days in plastic containers. In A. deliciosa and A. chinensis, the photosynthetic rate decreased markedly six days after starting waterlogging, and then leaf necrosis and defoliation occurred. All the leaves fell off by the ninth day of waterlogging. In contrast, a decrease in the photosynthetic rate and leaf disorder were hardly observed in A. macrosperma. In another experiment, three-year-old potted vines of ‘Hayward’ grafted on A. macrosperma [Fuchu] cuttings and A. deliciosa seedlings were waterlogged for 14 days. Leaf necrosis and defoliation occurred only in the ‘Hayward’ plants on the A. deliciosa seedlings, and all the vines defoliated seven days after the treatment completed. In these plants, the photosynthetic rate markedly decreased immediately after starting waterlogging. On the other hand, the photosynthetic rate was maintained at a relatively high level during and after the treatment in ‘Hayward’ on A. macrosperma [Fuchu] rootstock. After submersion for 10 days, the roots’ metabolic activity showed a significant reduction in ‘Hayward’ on the A. deliciosa seedling, but not on A. macrosperma [Fuchu]. These results showed that A. macrosperma is extremely tolerant to waterlogging, and the tolerance appeared in the kiwifruit scion grafted on A. macrosperma.

We evaluated the effective use of fallen needles of the Japanese black pine (Pinus thunbergii Parl.) collected at the world heritage site “Miho no Matsubara” as rooting media for blueberry (Vaccinium Spp.) cuttings to develop blueberry cultivation focusing on environmental and regional branding effects. We prepared media containing peat moss with the pine needles (v/v, 1 : 0 (0%), 3 : 1 (25%), 1 : 1 (50%), 1 : 3 (75%) and 0 : 1 (100%)), and compared the effects with those of conventional medium: peat moss and Kanuma pumice (v/v, 1 : 1) as a control. Soil pH in the control and media containing pine needles ranged from 4.4~4.7. The survival rate, shoot length, and root dry weight of the blueberry cuttings in the 25% medium were similar to those with the conventional media. Moreover, the survival rates of ‘Brightwell’ and ‘Misty’ in the 0~75% medium, and ‘Baldwin’ in the 0~50% medium, were similar to those with the conventional media. The shoot length of ‘Brightwell’ and ‘Baldwin’ in the 0~75% medium, and the root dry weight except for ‘Magnolia’ in the 0~75% medium were similar to those with the conventional media. The root dry weight of ‘Magnolia’ in all examined media showed no significant difference on comparison with the conventional media. The soil EC and total polyphenol content were increased with the addition of pine needles to the media, resulting in extremely high values: 10.2 for EC and 0.83 mg・g^–1 for polyphenol in the case of 100% medium. The low survival rate, shoot length, and root dry weight of the blueberry cuttings in the medium with a high percentage of pine needles might be ascribed to these high values. Collectively, we revealed that 25% media can produce a quality (shoot length and root dry weight) of blueberry cuttings with a high survival rate similar to that of the conventional media in all applied cultivars. Moreover, for ‘Brightwell’, up to 75% pine-containing medium can be used similarly to conventional media.

‘Koyama New Summer’ is a bud mutation of ‘Hyuganatsu’ (Citrus tamurana hort. ex. Tanaka). We examined the possibility of using fruit thinning to increase the production of seedless ‘Koyama New Summer’ fruit under natural pollination conditions. We found that 40% of the fruit produced in the field were seedless under natural pollination conditions. Examination of the relationship between the seed number and fruit quality showed that fruit with more seeds were larger in size, had a lower Brix value, and had thicker peel. Furthermore, many of the fruit with a prominent nipple at the apex contained seeds. Consequently, we considered that the transverse diameter of the fruit and presence of a prominent nipple at the apex could be used as indices for fruit thinning to increase seedless fruit production. We estimated the number of seeds and seedless fruit ratio in the harvested fruit by these two indices of fruit thinning. There was a high seedless fruit ratio in the harvested fruit when fruit thinning was undertaken in July by the prominent nipple at the apex of the fruit compared with no fruit thinning. It was considered that the prominent nipple at the apex of the fruit is easier to use as an index of fruit thinning than the transverse diameter of the fruit when having to decide on the criterion for annual fruit thinning. In conclusion, we recommend that fruit thinning is performed in July using the prominent nipple at the apex as an index to remove a part of seeded fruit, and so increase seedless fruit production.

To adapt to the recent low-temperature tendency during the apple flowering stage, we searched for apple cultivars capable of pollen germination at 10°C and suitable for pollination of the main cultivar ‘Fuji’. First, we analyzed in vitro pollen germination rates at 10, 15, and 20°C in 26 apple cultivars. As a result, the rate at 10°C was the highest in ‘Haruka’ expect for ‘Fuji’ and was the lowest in ‘Orin’ in two years. Next, we pollinated ‘Fuji’ with pollen of ‘Haruka’, ‘Orin’, and also ‘Shinano Gold’, which has become widespread in japan, at 10 or 20°C. When pollinated with ‘Orin’ pollen, the bearing rate of ‘Fuji’ decreased at 10°C. On the other hand, when pollinated with ‘Haruka’ and ‘Shinano Gold’ pollen, the bearing rate of ‘Fuji’ at 10°C was similar to that at 20°C. In addition, the pollen weight per 50 flowers in ‘Orin’ was the lowest among these 3 cultivars. Furthermore, even though the pollen of ‘Haruka’ and ‘Shinano Gold’ was used for pollination of ‘Fuji’, this did not affect the fruit shape or quality. These results indicate that pollen of ‘Haruka’ and ‘Shinano Gold’ is suitable for the fertilization of ‘Fuji’ under low temperature conditions, being superior to that of ‘Orin’.

The purpose of this study was to clarify flowering and shoot growth responses of plants to temperature and day length, which were observed in potted southern highbush blueberry grown under different environmental conditions after the end of harvest. Early flowering and new shoot growth were observed when plants were grown in a medium-temperature and short-day environment, but few fruits were harvested owing to few florets in the inflorescence, and new shoots were observed after harvest when plants were grown in a high-temperature and long-day environment. In contrast, new shoots began to grow prior to flowering in plants grown in a low-temperature and short-day environment. Thus, early harvesting was not expected. In comparison with semi-forcing culture, new shoots occurred prior to flowering, but earlier harvest was not obtained in plants moved from a high-temperature and short-day environment to a low-temperature and short-day environment, and finally to a medium-temperature and short-day environment. As new shoots were observed in plants grown in the low-temperature environment, the subsequent experiment was conducted to observe the responses of shoot growth to low-temperature using blueberry plants with yellow leaves. New shoots with green leaves emerged from plants grown in a low-temperature environment, and the iron content did not change; however, a higher manganese content was observed in new green leaves than in yellow leaves.

We revealed the effectiveness of new root loosening treatments (RLT) by a fork-shaped bucket (fork treatment), an inverted U-shaped bifurcated chisel (breaker treatment), a manual hoe for a tea garden (handhoe treatment), and a whole-layer loosening subsoiler mounted on a tractor (soil plowing treatment) on amelioration of freezing tolerance of young chestnut trees. The RLT-applied trees with fork and/or breaker attachment did not develop freezing injury compared with those receiving conventional RLT, even under the conditions where the control trees developed severe injury. Therefore, these 2 kinds of new RLT are suitable for improving RLT. Soil plowing by subsoiler attachment also ameliorated freezing injury compared with the control, although the effects were weaker than with conventional RLT. The manual RLT using a hoe decreased the non-freezing temperature of dormant buds the same as conventional RLT using a machine regardless of the number of applications, and the temperature was markedly lower than in the control. Moreover, this manual RLT suppressed the development of freezing injuries even in frequently injured orchards converted from rice fields. Thus, manual RLT is suitable for narrow orchards, where machines cannot enter. The mechanisms to prevent freezing injury were mainly associated with the low water content of the tree, although it was suggested that other physiological factors were also influential. RLT in November may prevent freezing injury development, which will be induced by a low temperature in early winter (hardening period), accelerating freezing tolerance development more than conventional December and/or January RLT. As mentioned above, the new RLT and season will have a greater effect than conventional RLT. These new RLT will expand suitability to a wide range of orchard conditions and tree heights.

In this study, the effects of flowering time on fruit drop and fruit quality at harvest were investigated in 7 citrus (‘Seinannohikari’, ‘Harehime’, ‘Shiranuhi’, ‘Setoka’, ‘Tsunokagayaki’, ‘Reikou’, and ‘Aoshima unshu’). Flowers were classified into three groups according to the time of flowering: early-flowering (before full bloom), middle-flowering (at full bloom), and late-flowering (after full bloom). ‘Seinannohikari’ and ‘Tsunokagayaki’ had lower fruiting rates in the early-flowering group than the late-flowering group. For other cultivars, there were no significant differences in the fruit setting rate between the early- and late-flowering groups. The effects of flowering time on the fruit weight at harvest differed among cultivars. The weights of ‘Aoshima unshu’, ‘Tsunokagayaki’, and ‘Reikou’ fruits in the early-flowering group were significantly lower than those in the late-flowering group, whereas the weights of ‘Harehime’ and ‘Setoka’ in the early-flowering group were significantly higher than those in the late-flowering group. For ‘Seinannohikari’ and ‘Shiranuhi’, the fruit weight showed no significant difference among fruits of early-, middle-, and late-flowering groups. In ‘Aoshima unshu’ and ‘Reikou’, sugar and acid contents per fruit were lower in the early-flowering group than in the late-flowering group. In ‘Harehime’ and ‘Setoka’, the sugar content per fruit was higher in the early-flowering group than in the late-flowering group. In ‘Setoka’, the acid content per fruit was higher in the early- and middle-flowering groups than in the late-flowering group. In ‘Seinannohikari’, ‘Shiranuhi’, and ‘Tsunokagayaki’, time of flowering had no effect on the sugar or acid content per fruit.

In this study, to obtain basic information for developing new cultivation systems and shortening the term of breeding in apple, we investigated the dormancy process and chill units (CU) required to break endodormancy of ‘Fuji’, ‘Orin’, ‘Jonathan’, ‘Ralls Janet’, and ‘Rome Beauty’, which is used in a cultivation system to produce two crops per year by defoliation in Indonesia, during two or three years. As a result, the CU required to break endodormancy of ‘Rome Beauty’, ‘Ralls Janet’, and ‘Jonathan’ were higher than that of other varieties. In contrast, ‘Orin’, which tends to flower unseasonably in Japan, required low CU. The deepest period of endodormancy was longer in ‘Fuji’, ‘Jonathan’, and ‘Ralls Janet’ than in the other cultivars. The time to enter the deepest period of endodormancy and duration of the break period of endodormancy in ‘Fuji’ were the same as in ‘Ralls Janet’. The time to enter the deepest period of endodormancy was earlier and the duration of the break period of endodormancy was longer in ‘Jonathan’ than in ‘Fuji’ and ‘Ralls Janet’. The time to enter of the deepest period of endodormancy was the latest in ‘Rome Beauty’. The time to enter the deepest period of endodormancy in ‘Orin’ was comparable to that in ‘Rome Beauty’, while ‘Rome Beauty’ had more than twice the duration of the deepest period of endodormancy than ‘Orin’. These results suggest that cultivars with a low CU required to break endodormancy and short duration of the deepest period of endodormancy, such as ‘Orin’, and those which entered the deepest period of endodormancy late, such as ‘Orin’ and ‘Rome Beauty’, may be suitable for a cultivation system that produces two crops per year by defoliation.

A storage technique for ‘Taishuu’ persimmon fruit was investigated using a polyethylene package, controlled O₂ and CO₂, and a low temperature to extend the storage period so they could be given as a year-end gift, as per the traditional Japanese custom. Packing in a 0.06-mm-thick polyethylene bag preserved flesh firmness 51 days after the start of storage under 0°C, but its taste deteriorated due to an off-odor. Packing with a microperforated film highly permeable to O₂ did not suppress the off-odor, while the presence of CO₂ absorbent in the bag suppressed off-odor production and maintained flesh crispness. An increase in the CO₂ concentration in the bag caused ethanol production in the flesh even under 20% O₂, suggesting that the accumulated CO₂ in the bag results in off-odor production. The combination of low temperature and CO₂ absorbent in the 0.06-mm polyethylene bag was proposed to extend the storage period for ‘Taishuu’.

The carotene content and its relationship with the characteristics of carrots was analyzed to identify an easier approach to assess the content without using general analytical methods. Carrots of the varieties ‘Hon-beni-kintoki’ (red color, true bred), ‘Koyo-2’ (orange color, F1), and ‘Shin-kuroda-gosun’ (orange color, true bred), cultivated in 1998/99 in Izunokuni City, Shizuoka Prefecture, Japan, were used in the study. Multiple regression analysis was performed using the carotene content as the dependent variable and root color (L*, a* and b*), moisture content, shape, and vigor as independent variables. As a result, a highly accurate (R² = 0.931, RPD = 3.7) formula for β-carotene content estimation was obtained when the root diameter, root moisture content, and leaf weight were set as independent variables. However, the accuracy for estimating the α-carotene content (except in ‘Hon-beni-kintoki’) was low (R² = 0.692, RPD = 2.1), even when the formula was set as optimal, with the root diameter and root moisture content as independent variables. Of note, the result of covariance analysis showed that the equations for estimating the β-carotene content of ‘Koyo-2’ and ‘Shin-Kuroda-Gosun’ were slightly different. Moreover, since it was necessary to average the data of 15 carrots cultivated under the same conditions to achieve sufficient estimate accuracy, it may be difficult to predict the carotene content of a single carrot using the estimation formula. However, this proposed equation could be applied for comparisons between groups.

In Japanese radish, internal browning is a physiological disorder caused by exposure to high temperatures. Due to the increase in global warming, it is feared that damage caused by this disorder will severely affect the stable summer production of the Japanese radish. We evaluated the tolerance to internal browning in 294 accessions of Japanese and other radishes. A local variety from Okinawa Prefecture, ‘Shimadaikon,’ was selected as the breeding material. As a result of repeated selections of progenies derived from the cross between ‘Shimadaikon’ and fixed line 10P13 under high-temperature conditions, we developed ‘Daikon chukanbohon No 6 go’, a Japanese radish parental line with a high tolerance to internal browning. ‘Daikon chukanbohon No 6 go’ showed stable tolerance to internal browning in eight test sites including Tsu, which has a high summer temperature. Several genes were involved in the tolerance to internal browning in this variety, and the tolerance was expressed as incompletely dominant in the F₁ generation. In the F₂ generation, a relatively large number of individuals showed the same tolerance level as ‘Daikon chukanbohon No 6 go’.