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Bulletin of the Tochigi Prefectural Agricultural Experiment Station

No. 77 (Issued in March, 2018)

Effect of Flower Thinning on Fruit Quality and Yield in Strawberry Cultivar ‘Tochigi i27 gou’(PDF:907KB)

  • Summary: When the conventional cultivation (CC) method without flower thinning was carried out, the brix of the strawberry cultivar ‘Tochigi i27 gou’ was the lowest from the second- or the third- inflorescences in flower clusters, followed by the increasing from higher order of inflorescences. In contrast, little change in acidity was observed. The results indicated that the fluctuation in the taste of strawberry fruit was due to that in the brix of the fruit between inflorescences. When the conventional flower thinning (CFT) method, in which the number of flowers per flower cluster was restricted to three (the first-to the third- inflorescences remained) or five (the first-to the fifth- inflorescences remained) followed by picking the respective higher orders of inflorescences was adopted, the fluctuation of the brix in the fruit was similar to that in the fruit grown using the CC method. In contrast, when the fruit was cultivated using the improved flower thinning (IFT) method, in which modified the CFT method by just picking the second inflorescence with maintaining the number of flowers per flower cluster, the fluctuation in the brix of the fruit was suppressed compared to that in the fruit grown using the CC method, along with the wholly improvement of the brix. In addition, the tendency was striking when the number of flowers per flower cluster was small.

 

No. 75 (Issued in March, 2017)

Effect of Soil Environment and Air Temperature on the Albinism Disorder Sentanmadaraka in Strawberry Cultivar ‘Tochigi i27 gou’(PDF:683KB)

  • Summary: This research was conducted to elucidate the effect of soil environment and air temperature on sentanmadaraka which is an albinism disorder occurring in fruits of strawberry cultivar ‘Tochigi i27 gou’ (proprietary name is Skyberry) in order to control their appearance. Initially, we investigated the effect of soil pH and amount of nitrogen fertilizer on the occurrence of sentanmadaraka. It was found that the condition developed at approximately pH 6.0, which is a standard value for strawberry cultivation. The amount of nitrogen fertilizer, however, had no effect. We then investigated the effect of air temperature, soil disinfectant and amount of nitrogen fertilizer. Occurrence of sentanmadaraka increased significantly at low temperature and high potency of soil disinfectant. Furthermore soil disinfectant elevated the concentration of ammonia nitrogen in the soil for 2 or 4 weeks after planting, which was considered to be the factor promoting the development of sentanmadaraka. In addition, the collapse of vacuoles and arrest of protoplasmic streaming of epidermal cells were obserbed microscopically in strawberries effected by sentanmadaraka. Accordingly, the symptoms of this disorder were considered to be caused by partial cell death of the epidermis.

Establishment of Freshness and Quality Maintenance Technology for Long-distance Transportation of Strawberry(PDF:538KB)

  • Summary: In order to establish a freshness maintenance technology for strawberry storage, we investigated storage temperature and packing method. Fruit quality was examined after 20 days of storage at a temperature of 0 °C or 5 °C with modified atmosphere (MA) package or no package. The combination of storage at a temperature of 0 °C with MA packing resulted in a high maintenance of strawberry freshness. Moreover, the generation of unpleasant odors in the package can be reduced by decreasing the amount of carbon dioxide in the package.

Strawberry Energy Saving Cultivation Technique Using a Thermal Storage Environment Control System(PDF:544KB)

  • Summary: In the thermal storage type of environmental control system, which is operational from the beginning of December to the beginning of March, the interior of the greenhouse is cooled by operating a heat pump. This makes it possible to reduce the ventilation using skylights. The daytime interior temperature of the greenhouse is controlled at 27 °C during both the morning and afternoon. The strawberry yield was increased by 12% to 17% compared to conventional cultivation using nutrient solution. Utility expenses decreased from 78% to 90% compared with the practice.

 

No. 74 (Issued in March, 2016)

Elucidation of the Growth Characteristics of Everbearing Strawberry under Year-Round Cultivation(PDF:564KB)

  • Summary: In this study, we aimed to establish a year-round cultivation system using the everbearing strawberry, which could then be used for basic research to study its growth and flowering characteristics, as well as to determine the effects of its forced year-round cultivation on the yield. First, the effects of environmental factors at the time of raising seedlings in forcing culture on flowering were studied using the everbearing varieties Natsuotome, Tochihitomi, Summerprincess, and Summertiara. Runner cutting time (between mid-June and July), day length, and nitrogen fertilization, were examined on how they affect the flowering date of each floral clusters after planting. Flowering of the first and second floral cluster in Natsuotome, Tochihitomi, and Summerprincess varieties occurred early in those plants that underwent runner cutting in mid-June. Next, we investigated the effects of runner cutting time and temperature on inflorescence flowering when day length conditions were set for 24 hours. The extent of flowering of each strains floral clusters was higher when runner cutting was early. The temperature becomes extremely low in the ward of the highest 35 ℃/30 ℃, this trend was clearly observed in the flowering strain rate of the second flower cluster later. We investigated yield and fruit quality in the everbearing varieties, Summertiara, Miyazakinatsuharuka, Awanatsuka, Summerfairy, and Natsuotome and compared these parameters with those of the junebearing variety Tochiotome. The everbearing varieties resulted in a higher yield but lower quality of fruit taste, and hardness than the Tochiotome. Lastly when Natsuotome was cultivated year-round, we found that crown-cooling improved yield properties. In addition, when the crown-cooling was performed from the planting season in the end of April until harvest 14 months later we obtained a yield of 13.7 t per 10 a.

Connection of Demand and Supply for Strawberry for Processing(PDF:562KB)

  • Summary: The Strawberries are eaten raw as fruit, yet they are also widely processed for use in confectionery and drinks. In this study, we investigated the change in planted area, harvest, and the import of strawberries. In years when a decline in planted area and harvest of strawberries was noted, fixed quantities of strawberries continued to be imported. In addition, we investigated the volumes of strawberry shipments for processing in the prefecture and the quantity of strawberries purchased by the prefecture processing company to clarify the actual import situation. In Tochigi, 660 tons, i.e., 2.5% of the total shipment volumes, was shipped for processing. The final products prepared using the shipped strawberries has an estimated worth of approximately 4,100 million yen. We bring about added value of approximately 30 times from strawberry approximately 130 million yen shipped for processing in Tochigi.

 

No. 73 (Issued in March, 2015)

Breeding of a New Everbearing Strawberry Cultivar ‘Natsuotome’(PDF:322KB)

  • Summary: ‘Natsuotome’ is a new everbearing strawberry cultivar released by the Tochigi Strawberry Research Center in 2011. This cultivar is harvested throughout the summer and autumn seasons, it has few flowers per inflorescence, does not have very thin inflorescences, and has a yield higher than that of the Tochihitomi cultivar. The fruits are cone shaped with vivid red skin. The sugar content and hardness of the fruits are similar to that of Tochititomi while their citric acid content is lower. The resistance to strawberry anthracnose, Fusarium wilt, and strawberry powdery mildew are higher in ‘Natsuotome’ than in Tochihitomi. In addition, the productivity of ‘Natsuotome’ is also higher than that of Tochihitomi between 200 to 800 meters of altitude.

Breeding of ‘Tochigi i 27 gou’ a strawberry cultivar producing extremely large fruits(PDF:532KB)

  • Summary: ‘Tochigi i27’ is a new strawberry cultivar released by the Tochigi Strawberry Research Center (Tochigi Prefectural Agricultural Experiment Station) in 2011. It was selected from hybrid seedlings resulting from a cross carried out in 2006 between ‘tochigi 20’ and ‘00-24-1’. The aim of this cross was to obtain a high performance cultivar for the forcing culture of strawberry in the Tochigi prefecture. ‘Tochigi i27’ is vigorous even in winter and it produces runners well. It has five to seven flowers per inflorescence and the fruits are very large 25 grams on average, conical, of deep orange color, and firmer than those of the ‘Tochiotome’ cultivar. The yield in ‘Tochigi i27’ cultivar is more than 20% higher than in ‘Tochiotome’. The sugar content and acidity in the fruits is lower than that in ‘Tochiotome’; however, the ratio of sweetness to acidity is similar to ‘Tochiotome’. In addition, the fruits are very juicy and of excellent flavor. Finally, ‘Tochigi i27’ is more resistant to anthracnose, Fusarium wilt, and strawberry powdery mildew than ‘Tochiotome’.

No. 63 (Issued in February, 2009)

Nutrient Solution Formula for a Closed Hydroponic System for Strawberries(PDF:341KB)

  • Summary: Prior investigations showed that the electrical conductivity (EC) of solutions within hydroponic substrates increased after February or later, and that Ca and SO42--S accumulated in the substrates when strawberries were grown on a closed hydroponic system using the nutrient solution ‘Ootsuka-A’ formula. Therefore, we evaluated whether strawberries grown using a hydroponic system with several improved nutrient solution formulae would result in lower Ca and SO42--S levels than those observed with the ‘Ootsuka-A’ formula. The most effective treatment was a 1/2 SO42--S formula. EC levels of the solution within the substrates fluctuated less, and the yield of fruits was higher with the 1/2 SO42--S formula than with other formulae. Control of the strawberry nutrient-solution concentration was studied in a hydroponic system using the 1/2 SO42--S formula. Adequate levels of EC in the supplying nutrient solution were 1.0 dS·m-1 from planting until the flowering period, increasing to 1.2 dS·m-1 from the flowering period until late February, then decreased in March to 1.0 dS·m-1. EC levels of the solution within the substrates were lower, and the yield of fruits was higher with this treatment. Therefore, we called the 1/2 SO42--S formula ‘Tochigi ichigo shoho’.

 

No. 61 (Issued in March, 2008)

Studies on the Hoeticultural Characteristics of Strawberry for the Development of
Year-round Production and the Rease and the Extension of a New Cultivar Adapted for It.(PDF:1,961KB)

  • Summary: The direction of flower cluster extension was investigated in micropropagated strawberry plants with no stolons. If micropropagated plants were planted at an angle of 20 to 25°, primary flower clusters developed in an inclined direction. However, primary flower clusters developed in the opposite direction if inclined pots were rotated by 1 80°, 40 days after the first inclination treatment. These results show that the direction of extension of primary flower clusters is determined geotropically during the period between flower bud differentiation and anthesis. Furthermore, it is likely that micropropagated plants will extend flower clusters to the aisle side if they are planted at an angle of 20 to 25° toward the aisle side.
    Effects of day length, planting time and plant nutritional conditions after planting on the development of axillary buds on primary crowns were investigated using ‘Tochiotome’ and ‘Nyoho’ strawberries, i.e., tipical cultivars for forcing culture. Axillary buds at the second to the fourth node from the apex of primary crowns usually developed into runners or axillary branches under long day condition in both cultivars. The number of axillary buds that developed into axillary buds or remained as dormant buds increased under short day conditions, especially in ‘Tochiotome’. As for the third and fourth node from the apex, late planting and poor nutritional conditions after planting increased the number of axillary buds that developed into axillary branches in ‘Nyoho’. On the other hand, poor nutritional condition after planting increased the number of axillary buds that remained as dormant buds and depressed the development of runners in ‘Tochiotome’ even when planting time was advanced. Effects of day length and temperature after transplanting and plant nutritional conditions before and after transplanting on the development of axillary buds of strawberry primary crowns were investigated using tipical strawberry cultivers for forcing culture, i.e., ‘Tochiotome’, ‘Nyoho’ and ‘Toyonoka’. When the maximum and average temperatures were higher than 35 and 25 °C respectively, in ‘Tochiotome’ axillary buds at node 2-4 from apex developed into runner even under poor nutritional and short day conditions, which usually inhibit the development of runner. Temperature exerts the strongest effect on the development of axillary buds as compared with day length and plant nutritional condition. High temperature and poor nutritional conditions after transplanting forced axillary buds to develop into runners. The developmental patterns of axillary bud were little affected by plant nutritional conditions while those were largely affected by cultivars. The results suggest that it is possible to control the developmental pattern of axillary buds by manipulating day length, temperature and plant nutritional condition.
    ‘Tochiotome’ strawberry’s pollen and pistil ability were investigated by forcing culture planting in early September. Compared with ‘Nyoho’, the germination percentage of ‘Tochiotome’ pollen was lower and the degree of decline in fertility after flowering was bigger. The fertility of ‘Tochiotome’ pistil was maintained during 3-4 days after flowering. It was shorter about 1-2 days than ‘Nyoho’ and also the degree of decline in the fertility after flowering was bigger. Compared with ‘Nyho’, ‘Tochiotome’ pollen and pistil was affected by the light condition, and especially the pollen fertility remarkably decreased by low light intensity. As for the stages of flower cluster, the period from coming of flower organ to coming out of flower bud was most influenced by low light intensity. From the facts described above, it is considered that ‘Tochiotome’ pollen and pistil ability are low by low light intensity and low temperature, and it may be possible to cause the deformity fruits by unfertilization. It becomes clear that ‘Tochiotome’ pistil tends toward conspicuous protogyny and growth difference between top pistil and bottom pistil on the receptacle is small. Therefore, it is considered that there is no unfertilization of top pistil in spite of whose fruits are extremely big.
    Leaf photosynthesis of strawberry plants showed remarkable diurnal change. The apparent photosynthetic rates (AP) were high in the morning, and declined by about 15% in the afternoon under the same light intensity. This afternoon reduction of AP was highly correlated to the reduction of stomatal diffusive conductance. Fv/Fm value from a chlorophyll fluorescence study did not show considerable diurnal change, suggesting that the light inhibition didn’t occur even under high irradiance in a fine day. On the other hand, leaf water potential was significantly low in the afternoon. Thus, it is concluded that the afternoon depression of leaf photosynthesis in strawberry plants is mainly caused by stomatal closure due to the reduced leaf water potential. The effects of prolonged night chilling and short day treatment with fertilization on the growth of terminal inflorescence and differentiation of primary axillary inflorescence were studied in strawberry plants that already differentiated terminal inflorescence in early August. Eight to ten days interruption of the treatment after the initial differentiation of terminal inflorescence increased the number of flowers in the terminal cluster. Supplemental application of fertilizers during interruption and prolonged night chilling and short day treatment accelerated the differentiation of primary axillary inflorescence. By transplanting strawberry plants to a productive field in early September after prolonged night chilling and short day treatment, it made possible to harvest fruits of terminal inflorescence from early October onward and fruits of the primary axillary inflorescence continuously. Therefore, early yield of strawberry fruits increased.
    Inbreeding is a great concern for strawberry plant breeders because of the repeated crossings among a limited number of breeding materials. Coefficients of inbreeding (CI) in recently developed cultivars of strawberry were calculated using a personal computer and a programming language, Prolog. The relation between CI and yield was also investigated in the strawberry. There was no correlation between the selection rate of F1 seedling plants and CI of those plants. In the strawberry breeding lines from Tochigi Branch, Tochigi Prefectural Agricultural Experiment Station, the correlation coefficient between CI and yield was -0.37, which was significant at the 1% level. The figure showed that strawberry plants with a CI less than 0.3 did not show any inbreeding depression. The CIs of several recently bred strawberry cultivars of the June-bearing type were approximately 0.2. CIs of ‘Tochiotome’, ‘Akihime’, ‘Sagahonoka’, ‘Amaou’, ‘Satumaotome’, ‘Hinosizuku’ and ‘Yayoihime’ were 0.261, 0.222, 0.257, 0.213, 0.257, 0.247 and 0.346, respectively. Those of CIs of ever-bearing type cultivars were approximately 0.1, except ‘Summer Princess’ and ‘Kiminohitomi’. Hypothetical diallel crossing among 15 representative June-bearing type cultivars resulted in CIs of their offsprings ranging from 0.067 to 0.440 with an average CI of 0.210.
    ‘Tochihitomi’ as a new ever-baring type cultivar was released. It can be used for flesh eating and business uses. The fruits of ‘Tochihitomi’ are high quality and yield is higher than other ever-baring type strawberries. The number of runners of ‘Tochihitomi’ is same as a June-baring type strawberry. It is possible for ‘Tochihitomi’ to cultivate in the area from 1100 m high to 400 m high above sea level. Transplanting to field from late April to early June has made it possible for harvesting early July. The yield was 1300 kg per 10 a, when ‘Tochihitomi’ was cultivated at 600 m high above sea level. This result shows that it is possible to prolong the summer-to-autumn cropping of ‘Tochihitomi’ under the condition that farmers have high skill and cultivation technics.

 

No. 58 (Issued in February, 2007)

Development of a New Cropping Type of Strawberry Using Water Curtain under Short-day and Night-cooling Conditions(PDF:735KB)

  • Summary: The purpose of this study was to prevent the none-differentiation in the axillary flower bud of strawberry under the high-temperature and long-day conditions, leading to long-term intermission of harvest. The new cropping type developed allowed the first axillary flower bud to differentiate using water curtain under the short-day and night-cooling conditions, resulting in the harvest from early October without long-term intermission. The photoperiod of eight hours was the most effective in the production of fruit of three plots; the other two periods were 12 and 16 hours. The yields of eight-hours plot were at most 95% greater than a conventional early cropping type. For the new type, the short-day treatment of axillary bud had been carried out simultaneously with the flower organ formation of terminal flower truss, leading to a decrease in the number of flowers, and 70 mg/pot of nitrogen had been normally applied. However, the nitrogen application of 210 mg/pot enhanced the differentiation of flower bud. Additionally, the bloom fruition of terminal flower bud became slightly earlier with a slightly increase in the number of flower, resulting in the yield from terminal flower truss greater by 20% than before. Indeed, the yield from terminal flower bud was increased by bed refrigeration technique. However, the review of the technique is required because of the delay of the bloom and harvest.

Breeding of a New Everbearing Strawberry Cultivar ‘Tochihitomi’(PDF:145KB)

  • Summary: ‘Tochihitomi’ is a new cultivar of everbearing strawberry, which is harvested throughout the summer and autumn seasons. In 1996 the strawberry was crossed the seedling of ‘Serienu’, and ‘Sachinoka’, followed by the application for the registration on the strawberry under Seeds and Seedings Law in July 2004.
    ‘Tochihitomi’ produced relatively numerous runners compared to most everbearing strawberries. The cultivar flowered without long-term intermission even under high-temperature and long-day conditions. The yield was similar to or greater than that of a standard cultivar ‘Pechika’. Among everbearing strawberries, the cultivar was relatively excellent in the taste. The skin of fruit was relatively firm, leading to the superiority in the shipping quality. ‘Tochihitomi’ was adapted for cultivation in the areas where were located at elevations of approximately 500 m or higher. It is necessary to control temperature using shading materials to prevent the occurrence of malformed fruit, which takes place frequently in summer.

 

No. 51 (Issued in December, 2002)

Production of Young Plants of cultivar ‘Tochiotome’ by Aerial Shoot Cutting using Cryptomoss Mixed Medium(PDF:1,464KB)

  • Summary: Propagation from aerial runner cuttings, untimely flower bud emergence, and fruit productivity in the field were investigated in relation to the production of young daughter plants of cultivar ‘Tochiotome’ by the method of aerial soot cutting. The number of young plants obtained from aerial shoot cuttings was about 20% less than that obtained from ground-grown plants. About a 60 ~ 100% increase of young plants was observed when the mother plants were set beds in mid-March as compared to planting in mid-April. The maximum number of daughter plants was obtained when a concentration of EC 1.0-1.3 dS/m Ootsuka A culture medium was supplied to the mother plants. As the number of leaves on a cutting had small effect on productivity in the field, young plants with two to six leaves can be used satisfactorily if productivity is the sole consideration. However, as plants that had more than four leaves when the cuttings were prepared tend to show untimely flower bud emergence, it is desirable to prepare cuttings with leaves of three or less in number.

 

No. 50 (Issued in December, 2001)

New Strawberry Cultivar ‘Tochihime’(PDF:865KB)

  • Summary: 'Tochihime’ is a new strawberry cultivar, selected from hybrid seedlings of a cross between ‘Tochinomine’ and ‘Kurume49’. This cross was made in 1990 to obtain a high performance cultivar for forcing culture in Tochigi prefecture. The characteristics of the cultivar are described here.
    ‘Tochihime’ is vigorous and produces abundant runners. The leaves are large and dark green. The degree of dormancy is a little heavier than ‘Nyoho’. Similar to ‘Nyoho’ and ‘Tochiotome’, the flower bud of the terminal cluster is initiated late in September. The number of flowers in the terminal cluster is thirteen on average. The fruits are as large as seventeen grams, conical, and a very shiny deep scarlet color. The firmness of the fruit is similar to or a little less than ‘Nyoho’. The soluble solid content is similar to ‘Nyoho’, but titrated acidity is lower than ‘Tochiotome’. The texture is very juicy. The yield of ‘Tochihime’ is higher than ‘Nyoho’ and ‘Tochiotome’, and the harvesting is continuous. The resistance to powdery mildew and anthracnose is similar to ‘Nyoho’. ‘Tochihime’ is suitable for forcing culture in Tochigi prefecture and for roadside-stand-market operations, pick-your-own, and sightseeing farms.

 Effect of electric illumination, carbon dioxide supplementation and underground heating on the growth and yield of strawberry ‘Tochiotome’ in forcing culture(PDF:1,094KB)

  • Summary: The effects of culture management technologies, such as electric illumination, carbon dioxide supply, and underground heating, on the growth and yield of strawberry ‘Tochiotome’ in forcing culture were investigated. Growth of plants in severe cold was promoted by electric illumination. The yield after the second axillary flower cluster stage was increased, resulting in an increase in total yield. Electric illumination should be started in early to mid-December in Short-day and low night temperature treatment of late-August planting, or in the latter half of November if the treatment of mid-September planting. Short-day and low night temperature treatment and Carbon dioxide supplementation was less effective at maintaining plant growth. Nevertheless, it resulted in better yield, since earlier harvest after the first axillary flower cluster stage shortened the harvest interval. Underground heating reduced plant growth in severe cold, promoted leaf opening, and increased the number and weight of leaves after the second axillary flower cluster stage, resulting in better yield. Underground heating should be started by the first half of December. Use of a combination of these three culture management technologies provided synergistic effects compared to their use in isolation. The combination of electric illumination, to maintain leaf area, and carbon dioxide supplementation, to promote photosynthetic capacity of leaves, had the best synergistic effect.

Pollen and Pistil Fertility of ‘Tochiotome’ Strawberry(PDF:1,294KB)

  • Summary: ‘Tochiotome’ Strawberry’s pollen and pistil were investigated by forcing culture planting in early September. Compared with ‘Nyoho’ Strawberry, the germination percentage of ‘Tochiotome’ pollen was below, also the extent of decline in fertility after flowering was bigger compared with ‘Nyoho’, ‘Tochiotome’ pollen had a lower germination percentage and showed a bigger decline in fertility after flowering. The fertility of ‘Tochiotome’ pistils was maintained for 3-4 days after flowering, about 1-2 days less than ‘Nyoho’. Also the extent of fertility loss after flowering was bigger for ‘Tochiotome’. Compared with ‘Nyoho’, ‘Tochiotome’ pollen and pistils were more affected by the light conditions during growth, in particular the pollen fertility of ‘Tochiotome’ fell remarkably under low light intensity. As to the effect of the developmental stage of the flower cluster, the period between flower organ formation and flower bud emergence was the most sensitive to the adverse effects of low light intensity. From the facts described above, ‘Tochiotome’ pollen and pistil are below in low light intensity and low temperature, it is considered that there is some possibility of arising deformity fruits caused by unfertilization, These findings raise the possibility that low light intensity and low temperature may lead to deformed fruits on ‘Tochiotome’ because of incomplete fertilization. To prevent incomplete fertilization, it is necessary to hasten pollen germination by maintaining 25 °C in the green house during the daytime. Also, it is important that the plants be pollinated by honeybees within a few days after flowering. During our study, it became clear that the ‘Tochiotome’ pistil tends toward conspicuous protogyny and the growth difference between the top pistil and bottom pistil on the receptacle is small. Therefore it is considered that there is no incomplete fertilization of the top pistil even though the fruits are extremely big.

 

No. 46 (Issued in December, 1997)

Establishing the Strawberry Production in Summer and Autumn(PDF:709KB)

  • Summary: To establish the strawberry production in summer and autumn in the northern part of Tochigi prefecture, we investigated on the strawberry variety, seedling raising method, planting time, flower thinning and pest protection. As the result, we established the technology to produce two tons of strawberry per ten ares through July to October.
    For the strawberry production in summer and autumn, ever-bearing variety ‘Summer Berry’ is the best suitable one considering the continuous flower bud formation, fruit yield and fruit quality. Recommended cultivation method is as follows: Mother plants are transplanted in the middle of March and runner plants are planted temporarily in late September or early October. Daughter plants whose crown diameter is 10 mm are transplanted in the middle of April. Flower trusses, which begin to emerge after the daughter plants were transplanted, should be removed until the end of May to increase the fruit yield. Plants are covered with plastic roofs to prevent rain and mulched with white polyethylene sheets in early or the middle of June. They are grown under the shading material (40% reduction) after the rainy season was over until early or the middle of September to protect them from high temperature. Covering the plants with cheese cloth (insect prevention net) with 1.04 mm mesh in early June is effective for the control of slips and it reduces the pesticide application to half.

 

No. 44 (Issued in December, 1996)

New Strawberry Cultivar ‘Tochiotome’(PDF:1,690KB)

  • Summary: ‘Tochiotome’ is a new strawberry cultivar released by Tochigi Branch, Tochigi Prefectural Agricultural Experiment Station ill l996. It was selected from hybrid seedlings of a cross between ‘Kurume 49’ (‘Toyonoka’/’Nyoho’) and ‘Tochinomine’ (‘Kei 511’/’Nyoho’) crossed in 1990 to obtain a high performance cultivar for forcing culture in Tochigi prefecture.
    ‘Tochiotome’ is vigorous and produces runners well. The leaves are large and dark green. The degree of dormancy is similar to ‘Nyoho’, the most popular cultivar for forcing culture. The number of flowers per inflorescence is fifteen on the average. The yield is higher than ‘Nyoho’. The fruits are large as fifteen grams, conical, and have very shining scarlet color, so they look very good. They have firm peel and flesh so the keeping quality is high. They have strong sweetness, weak acidity, and very juicy, so the taste is excellent. The resistance to powdery mildew anthracnose slmilar to ‘Nyoho’.

 

No. 42 (Issued in December, 1994)

A new laborsaving method for raising strawberry seedlings using cell trays(PDF:1,078KB)

  • Summary: A new laborsaving method for raising strawberry seedlings has been requested, because the conventional method needs much labor and material. So we studied on feasibility and efficiency of a new method for raising strawberry seedlings by using cell trays.
    l. If we transplant seedlings to the cell trays when they began rooting and their leaf number were 2.1, it was easy to operate. We could get seedlings whose weight 15 to 20 grams and crown diameters were eight to nine millimeters if we applied 20 mg nitrogen fertilizers par seedlings.
    2. Fruits yield of the plants raised by the new method was high when the planted seedlings were big. Medium and small seedlings, which are easier to handle, yielded 90% of those raised by the conventional method if nitrogen fertilizer was adequately applied. Plants treated with night-chillng from early or mid August yielded more than those treated from late August.
    3. We could start night-chlling treatment on three weeks after they transplanted to the cell trays. So we could shorten the raising period by the new method.
    4. Flower-bud formation of the plants raised by the new method was a little delayed than that of the conventionally raised plants, but the flowering date was the same. Leaf number or nutritional condition may influence flower bud formation.
    5. During the late raising period, the seedlings raised by the new method showed very long appearance plastochron compared with those raised by conventional method. This fact indicates poor nutritional condition. However appearance plastochron after final transplanting was a bit short, and petiole length and leaf area were the same as those of the conventionally raised plants.
    6. We improved cell tray for strawberry. The improved one is made from foaming polystyrene whose size is 30 x 60 cm and has 45 cylindrical cells whose volume is 130 ml each. We need only one sixth compost and one fourth area compared with conventional method.
    7. We concluded that new method for raising strawberry seedlings using the cell trays is laborsaving. , practical and feasible.

 

No. 40 (Issued in December, 1993)

Effects of Starting Date of Short-day and Low Night Temperature Treatment on Flowering and Fruiting of Strawberry cv. Nyoho(PDF:568KB)

  • Summary: Short-day and low night temperature treatment is commonly practiced to accelerate flower bud initiation of strawberry in Japan. To accelerate the harvesting time more, we investigated the effects of the starting date of short day and low night temperature treatment on flower bud initiation, fruits quality and yield of strawberry cv. Nyoho. The results are as follows:
    1. The earlier the treatment starting date was, the earlier flower bud differentiation and harvesting time were. Days from the treatment starting date to flower bud initiation was varied from 18 to 34 depended on the treatment starting date.
    2. When we started the treatment on June 25, we could harvest fruits from mid-September (about 90 days after the beginning of treatment). When we started the treatment on August 5, we could harvest fruits from early or mid-November (about 100 days after the beginning of the treatment).
    3. There was general decrease in the fruit enlargement with advanced treatment starting date. Therefore, fruits yield before the end of December was low when we start treatment early (on June 25 or July 5).
    4. The earlier the treatment starting date was, the lower the brix of fruits was. According as the harvesting time became late, the brix of the fruits became higher and the acidity of fruits became lower.

Effects of the Day and Night Temperature during Short-day and Low Night Temperature Treatment on Flower Bud Initiation of Strawberry(PDF:456KB)

  • Summary: Short-day and low night temperature treatment is commonly practiced to accelerate flower bud initiation of strawberry in Japan. To accelerate the harvesting time more, we investigated the effects of the day and night temperature during short-day and low temperature treatment on flower bud initiation of strawberry. The results are as follows:
    1. Night temperature had no effects on flower bud initiation of cv. Nyoho no matter when the treatment was started. The treatment starting date had an effect on flower bud initiation. Cumulative hours above 30 °C had significantly correlated to the treatment days required for flower bud initiation. Every six or seven cumulative hours above 30 °C, flower bud initiation of cv. Nyoho delayed one day.
    2. Night temperature ranged from 10 to 18 °C did not affect flower bud initiation of cv. Toyonoka and Nyoho.
    3. Inhibitory effect of high day temperature was significant when the day temperature was higher than 30 °C with ‘Nyoho’, 35 °C with ‘Toyonoka’, ‘Hokowase’ and ‘Kurume 51’. Degree of the delaying effect of high day temperature on flowering was greater with the order of ‘Hokowase’, ‘Toyonoka’, ‘Nyoho’ and ‘Kurume 51’.

Effects of some Factors concerning with Chilling Treatment under Dark Condition on Flower Bud Initiation, Flowering and Yield of Strawberry cv. ‘Nyoho’(PDF:787KB)

  • Summary: This study was carried out to clarify the effects of applied nitrogen amount in nursery, length of nursery period, starting stage of chilling treatment under dark condition, length and temperature of the treatment, and acclimatization after the treatment on flower bud initiation, flowering and yield of strawberry cv. Nyoho grown in pots.
    Low nitrogen application (90-130 mg nitrogen per plant), that made nitrogen content of leaves at the beginning of chilling treatment less than 1.4%, was favorable for flower bud initiation. Under the condition of heavy nitrogen application (170-210 mg nitrogen per plant), that made nitrogen content of leaves more than 1.8%, flower bud initiation and flowering time were very delayed and yield at an early harvesting stage was low.
    Late treatment (started on August 15 or 26) was favorable for flower bud initiation, flowering time and yield than early treatment (started on August 5). Long nursery period (80 days) was favorable for flower bud initiation and yield at an early harvesting stage. In case that nursery period is short (50 days), we may have to start the chilling treatment under dark condition at late August. The effects of the treatment length and acclimatization were small.
    Relatively high treatment temperature (18 °C constant or 18 °C day/13 °C night) was favorable for flower bud initiation than low treatment temperature (13 °C constant).

New Strawberry Cultivar ‘Tochinomine’(PDF:850KB)

  • Summary: The new strawberry cultivar ‘Tochinomine’ was named 1992 and registered in 1993. It was selected from hybrid seedling produced from crossing between ‘Kei 511’ (‘Florida 69-266’/’Reiko’ crossed in 1980) and ‘Nyoho’ (released in 1984) in 1984 in order to obtain the cultivar adaptive to semi-forcing culture in Tochigi Prefecture.
    The characteristics of ‘Tochinomine’ are as follows:
    1. Growth habit: Vigorous, large and thick green leaves.
    2. Flower formation: flower bud of terminal cluster is initiated early in October, is about 7 days late to the most popular cultivar ‘Nyoho’.
    3. Dormancy: little heavier than ‘Nyoho’, so optimum time for covering of plastic film in semi-forcing culture is early in December (above 300 hr. below 5 °C).
    4. Fruit: long cone, relatively large, 18 to 20 g, glossy skin with deep scarlet color, solid flesh with aroma, very sweet, excellent taste.
    5. Chemical characteristics of the fruits: soluble solid content, 9.0 to 10.0 degree in Brix, titrated acidity, 0.7 to 0.9%.
    6. Yield: 450-500 g per plant from March to May in semi-forcing culture.
    7. Resistance to disease: strong to powdery mildew.
    8. Adaptation culture: semi-forcing culture, and also forcing culture.

 

No. 39 (Issued in December, 1992)

A survey of virus diseases of strawberry in Tochigi Prefecture(PDF:539KB)

  • Summary: Because the virus infection has been very severe in the strawberry producing districts in Tochigi Prefecture, the project of distribution of virus free plants was started in 1971. Since then about 20 years have passed, so we carried out a sampling test in 1989 and 1990 to know the present situation of virus infection in strawberry.
    l. In 1989, strawberry crinkle virus (SCrV), strawberry mottle virus (SMoV) and strawberry mild yellow edge virus (SMYEV) were observed in six out of nine strawberry producing district. The percentage of infected plants ranged from 20 to 40%. But the damage by virus diseases was very light wherever virus infection was observed. The result of 1990 was similar to that of 1989.
    2. The percentage of infection in plants of which virus free mother plants were renewed every other year was higher than that of plants renewed every year. The damage by virus diseases in the former was heavier than in the latter.
    3. The growth rate and the yield of infected plants were slightly lower than those of uninfected plants.
    4. From these results, it is considered that the damage of strawberry by virus diseases has decreased remarkably during 20 years.

 

No. 31 (Issued in October, 1985)

Nyoho, a New Strawberry Cultivar(PDF:1,082KB)

  • Summary: In order to obtain a new strawberry cultivar adaptive to forcing culture in Tochigi Prefecture, breeding has been carried out since 1969 and ‘Nyoho’ was developed in 1985
    The characteristics of ‘Nyoho’ are as follows:
    1. Growth habit: vigorous; leaves large and glossy deep green.
    2. Dormancy: as light as in Reiko; about 500 hr. below 5 °C required for dormancy breaking.
    3. Fruit: conic, relatively small, 12 to 13 g, the skin glossy scarlet, firm, and the fresh strong with high flavor.
    4. Chemical characteristics of the fruit: soluble solid content 8.0 to 9.0 degree in Brix, titrated acidity 0.6 to 1.0%.
    5. Yield: 500-600 g per plant from December to May.
    6. Flower: flowers of terminal cluster have normal anthers, the first to second flowers of axillary cluster occasionally with poorly developed anthers.
    7. Resistance to disease: comparatively resistant to powdery mildew, but susceptible to Fusarium wilt disease.
    8. The optimum time for covering of plastic film is the middle of October and the harvesting season begins in December.
    ‘Nyoho’ is adapted to forcing culture without artificial lighting for longday treatment and gibberellic acid spraying for elongating the plant.

Hydrolytic Enzyme Activities in Strawberry Greenhouse Fields under Different Soil Management.(PDF:750KB)

  • Summary: The present paper deals with the effects of different soil management during fallow period on strawberry yield and soil enzyme activities at harvesting time. The results are summarized as follows:
    Ninhydrine positive substances, crude protein and NH4-N in soils were increased by the cultivation of sorghum or paddy rice. The soil enzyme activities were enhanced by their cultivation but not by the cultivation of cabbage.
    The application of sawdust compost in soils raised soil enzyme activities higher for protease, L-glutaminase, β-acetylglucosaminidase and β-glucosidase (taking part in the hydrolysis of organic N or C) than for phosphodiestrase and phosphomonoesterase (ditto of organic P). The influences of the soil management during fallow period were weakened by the application of the sawdust compost in soils.
    The strawberry yield was increased by the application of the sawdust compost and correlated with the activities of protease and phosphodiesterase in soils. Further, the other soil enzyme activities were generally raised in the high-yield plots.
    The soil enzyme activities were highly correlated with soil organic matter such as
    T-C, T-N crude protein and ninhydrine positive substances.

 

No. 27 (Issued in October, 1981)

Studies on the Forcing Culture of Strawberry. (III)
Effects of Light Intensity and Night Temperature on the Growth, Yield and Fruit Quality and its Economical Consideration.(PDF:416KB)

  • Summary: Effects of light intensity of supplemental illumination and night temperature on the growth, flowering, yield and maturity of forcing strawberry cv. Hokowase were investigated.
    Plants received four treatments: a factor combination of two levels of light intensity (40 lux, 10 lux) and two levels of night temperature (9 °C, 5 °C).
    Vegetative growth was enhanced by high light intensity, while flowering date and maturing time was promoted by high night temperature. Early yield (until January 22) was slightly increased at high night temperature but total yield (until late May) was of maximal under the combination of low night temperature and high light intensity.
    As compared the gross receipts with the total cost of heating and electrical charges, the income in the treatment of low night temperature and high light intensity was greater than the others.

 

No. 26 (Issued in October, 1980)

Studies on the Forcing Culture of Strawberry (II)
Effects of intensity of illumination and its Systems on the Growth and Yield of Strawberry(PDF:567KB)

  • No English summary

 

No. 23 (Issued in September, 1977)

Studies on the Forcing Culture of Strawberry. (I)
Effects of various Nitrate Levels in Strawberry Petiole on the Flower Formation and Yield.(PDF:578KB)

  • No English summary

 

No. 21 (Issued in October, 1976)

On the Increase of Productivity by Virus-Free Plants of Strawberry. (III)
Renewal Periods of the Mother Stocks.(PDF:445KB)

  • No English summary

 

No. 18 (Issued in October, 1974)

On the Increase of Productivity by Virus-Free Plants of Strawberry. (II)
On the Beginning Time of Forcing with Some Cropping Types of ‘Danner’.(PDF:527KB)

  • No English summary

 

No. 17 (Issued in October, 1973)

On the Occurrence of Malformed Fruit in Strawberry. (V)
On Imperfect Stamens caused by Low Temperature before Plastic Covering.(PDF:436KB)

  • No English summary

On the Increase of Productivity by Virus-Free Plants of Strawberry. (I)
Infection of Virus Disease and Yield of ‘Donner’ Nursery Plants Collected from Various Areas in Tochigi Prefecture.(PDF:420KB)

  • No English summary

 

No. 16 (Issued in October, 1972)

Seasonal Changes of the Top and Root Growth for Various Croping Types on Danner Strawberry Plants.(PDF:408KB)

  • No English summary

Effect of the Cold Storage Period Correlated Digging Date on Strawberry Plants for Early Spring Bearing.(PDF:449KB)

  • No English summary

On the Occurrence of Malformed Fruit in Strawberry. (IV)
Effects of High Temperature in Field.(PDF:413KB)

  • No English summary

 

No. 15 (Issued in October, 1971)

On the occurrence of malformed fruit in strawberry. (III)
Effects of agricultural chemicals sprays.(PDF:386KB)

  • No English summary

 

No. 14 (Issued in October, 1970)

On the occurrence of malformed fruit in strawberry. (II)
The function of flowering and pistil and pollen.(PDF:550KB)

  • No English summary

Control of air temperature for early spring bearing by cold stored strawberry plant.(PDF:407KB)

  • No English summary

Effect of root temperature and its combination with air temperature on the growth and yield of strawberry plants inphytotron.(PDF:496KB)

  • No English summar

 

No. 13 (Issued in November, 1969)

On the occurrence of malformed fruit in strawberry. I.
Effect of high temperature.(PDF:329KB)

  • No English summary

 

No. 10 (Issued in February, 1967)

Ecological studies on the promoting of growth and fruiting of strawberry plant under semi forcing culture. III.
Tests of cold treatment for practical use.(PDF:504KB)

  • No English summary

 

No. 8 (Issued in December, 1964)

Ecological studies on the promoting of growth and fruiting of strawberry plants under semi forcing culture. I.
On the covering times of vinyle film tunnel.(PDF:462KB)

  • No English summary

Studies on the forcing culture of strawberry. III.
Effects of shade treatments for set at the cool plateau.(PDF:517KB)

  • No English summary

 

No. 7 (Issued in December, 1963)

Studies on the forcing culture of strawberry. II.
Effects of short-day treatments for strawberry set at the cool plateau.(PDF:523KB)

  • No English summary

 

No. 6 (Issued in December, 1962)

Studies on the plant age and spacing of semi-forcing culture of strawberry under vinyle film tunnel cover.(PDF:557KB)

  • Summary: This is a report of the study conducted from 1958 to 1961. In the experiment of plant age, runner plants were separated from the mother plants and were transplanted to the cold-bed on July 10, August l, 20 and September 10, with variety kogyoku in 1958 and Danner in 1961. Each plot (6.48 m2) of the spacing experiment included 85, 60, 39, 27 and 16 plants, which were divided into two groups, large and small, according to their size at the time of runner separating. Therefore 10 plots were tested.
    l. In the plant age experiment, the best plant growth and the heaviest berry yield were obtained from the plants which were early separated. Delaying of the time of runner separating seemed apt to accelerate the flowering time and then increase the early fruits, moreover average fruit weight was heavy and ratio of superior fruit was high.
    2. On the spacing experiment it was as follows:
    l) The number of leaves of large plant were much more than in small plant. The number of leaves per a plot increased with the plant density, while it was fewer per a plant in the same case.
    2) The total number of fruits increased in parallel with the number of leaves per a plot. However, the number of marketable fruits showed rather decrease when the number of leaves per a plot reached more than approximately 1200.
    3) Decreased yield of the close spacing plots of large plant was due mainly to numerous rotted fruits.
    4) The early yield differed according to plant size and spacing. In general, the heavier early yields were obtained from the small plants or wide spacing plots. For the large plants, wide spacing, and for the small plants, rather close spacing showed good results.
    5) The desirable spacing of plants for the semi-forcing strawberry culture under vinyle film tunnel cover varied by plant size; it was 28-40 cm in large plants and about 25 cm in small ones.

 

No. 4 (Issued in October, 1960)

Studies on the forcing culture of strawberry (1)
On the time of transplanting of set at the cool plateau.(PDF:922KB)

  • Summary: 1) Fundamental problems of the forcing culture of strawberry were investigated in 1958 and 1959. The sets of a variety Hukuba were transplanted, at different times, from the warmer land, Sano, on to the cool Senzyogahara plateau, 1400 m high above the sea level. And some characters of the sets were compared with the sets grown at Sano.
    2) During these two years, the mean temperature was always below 18 °C at the Senzyogahara plateau. Under such climatic condition, the date of flower bud formation of the sets were about September 20 independent of transplanting time, which was about two weeks earlier than the date at Sano.
    3) Better sets were obtained by transplanting into the plateau before the first ten days of August, and the later than this period, the poorer the sets became. The poor sets were accelerated in the time of both flower bud development and harvesting.
    4) The beginning of strawberry harvesting of the sets grown at the plateau was in the flowerclusters middle of December. It was about 35 days earlier in the 1st-, 20 days in the 2nd-, and 10 days in the 3rd- than the sets grown at Sano. The plateau grown sets were heavier in early yield.
    5) The optimum days of transplanting of strawberry set on to the cool plateau were determined to be the last ten days of August.

 

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