To determine the potential for the breeding of tendril-less sweetpea cut flower cultivars, an awareness survey was conducted among sweetpea farmers from the 97 sweetpea farms in Miyazaki Prefecture, Japan, in 2009. The sweetpea farmers included farm managers and their family members. The questions included in the survey pertained to the growing area used, factors responsible for the most significant production management costs, most laborious cultural practices, degree of necessity of tendrils, degree of eagerness to grow tendril-less cultivars, and desirable varietal characteristics. The survey showed that the average growing area for the 46 farm managers who answered this question in the survey was 17.3 a, and the growing area per laborer was 3.2 a. There was a significant positive correlation between the number of laborers and sweetpea-growing area (r = 0.91**). The answers were divided according to 3 attributes pertaining to the farmers and examined. The attributes were: (1) the position of the participant, i.e., farm manager or family member; (2) the kind of labor used on the farm, i.e., family or employed labor; and (3) the size of the sweetpea-growing area. In reply to the question on the factors responsible for the most significant production management costs, the farm managers and family members selected employment costs, the family labor farmers selected the shipping costs, and the employed labor farmers selected the employment costs. The farmers who had a sweetpea growing area smaller than 10 a selected shipping as the most significant production management cost, whereas the farmers who had a sweetpea growing area larger than 10 a selected the employment costs. In response to the question on the most laborious cultural practices, “Yuin,” i.e., training pertaining to removing the tendrils and lateral shoots, and “Tsurusage,” i.e., training pertaining to resetting of the growing point from the top of the supporting net to a lower position in the supporting net, were selected, regardless of the attribute of each farmer. In response to the question on the degree of necessity of tendrils, “either” was selected, regardless of the attribute of each farmer. In response to the question on the degree of eagerness to grow tendril-less cultivars, the farm managers selected the option “add the tendril-less cultivar in candidate cultivars.” This result showed that the farm managers expected that the absence of tendrils in these cultivars would be a labor-saving trait. In response to the question on desirable varietal characteristics, both farm managers and family members selected resistance to bud drop, a long vase life, high ratio of sales to production, and high yields more often than labor-saving traits, in spite of the response given to the question on the degree of eagerness to grow tendril-less cultivars.
We investigated leaf and flower bud characteristics in tetraploid plants and 2x-4x-4x ploidy chimeras from 20 citrus cultivars and strains induced by colchicine treatment. With regard to tetraploid plants, the leaf thickness was larger and stomatal density was smaller than the corresponding characteristics of diploid plants in all cultivars and strains. On the other hand, there were no characteristics considered to show a significant difference between tetraploid and diploid plants in all cultivars and strains regarding the flower bud. With regard to 2x-4x-4x ploidy chimeras, the leaf thickness was larger than that of diploid plants in all cultivars and strains, but the stomatal density did not exhibit a definite tendency. Furthermore, there were no characteristics considered to show a significant difference between 2x-4x-4x ploidy chimeras and diploid plants in all cultivars and strains for the flower bud. These characteristics were available for roughly selecting tetraploid plants and 2x-4x-4x ploidy chimeras from a colchicine treated population, leading to efficient ploidy analysis by flow cytometry.
In order to improve the quality of tomato nursery plants in high-temperature periods, we investigated the effect of root-zone cooling of the potted seedlings on growth, establishment, and subsequent fruit yield. We utilized cold water passed through a heat exchange pipe which contacted the pot surface of tomato seedlings to reduce the growing medium temperature. The root growth was enhanced by continuous (24 h) cooling, while both shoot and root growths were enhanced by daytime (7:00~19:00) cooling. On the other hand, night-time (19:00~7:00) cooling repressed shoot growth. Enhanced root growth by root-zone cooling improved plant establishment. Moreover, daytime root-zone cooling during the pot seedling stage increased the subsequent fruit yield. Daytime root-zone cooling for 8 h (9:00~17:00) had nearly the same effects as those for 12 h (7:00~19:00). Based on the above findings, under this experimental condition, tomato seedlings with a high yield potential in a low-node-order pinching system at a high planting density could be produced by cooling the center of the medium by 3~4°C during particularly high-temperature hours.
Long-day treatments were applied to everbearing strawberry (Fragaria × ananassa Duch.) ‘Natsuakari’ before planting to accelerate flower initiation for the autumn harvest. Twenty-four-hour day length treatment for one month promoted the flower initiation of runner plants potted on May 30, June 17, July 1, and in the previous July. The yields of the first-year runner plants that were subjected to 24-h treatment were not lower than those of the plants potted in the previous July. An increase in day length led to a corresponding increase in flower initiation. Two weeks of treatment was sufficient for flower initiation in all the plants that underwent 24-h day length treatment or 4-h night interruption treatment. In the case of plants that underwent 16-h day length treatment, anthesis was observed in all of these plants after treatment for a total of one month. Three different planting dates after 24-h continuous or cyclic lighting (15 min·h−1, overnight) treatments were investigated. As a result of 24-h continuous lighting for 3 weeks, harvesting could be initiated from early September for plants that were planted on July 28, but the yield in October was higher for the plants that were planted on August 10. Not all of the plants that were planted on September 2 could be harvested by December. Cyclic lighting was markedly less effective for flowering than continuous lighting.
We examined indices of waterlogging tolerance in lettuce and broccoli, which will be helpful in selecting and breeding cultivars with a high waterlogging tolerance. After 5 days waterlogging of lettuce and broccoli cultivars, differences in the rate of decrease in the root dry weight were observed, indicating the existence of varietal differences in waterlogging tolerance. In the experiments over 5 days waterlogging of lettuce cultivars, the rate of decrease in the root dry weight showed significant negative correlations with the acetaldehyde-producing ability 1 hour after roots were anaerobically treated with nitrogen gas, and with the ethanol-producing ability at 1 and 15 hours after roots were anaerobically treated with nitrogen gas, in vitro. Thus, these measured values can be used as indices of waterlogging tolerance in lettuce. In contrast, after waterlogging, broccoli showed no correlations between the degree of decrease in the root dry weight and the measured values of the acetaldehyde- or ethanol-producing ability.
We investigated fruit set and fruit quality of a hexaploid ‘Fuyu’ pollinated with pollen from two different strains of nonaploid persimmon to explore the possibility of a novel cultural practice for seedless ‘Fuyu’ fruit production. Pollen from both nonaploid strains germinated normally, with their pollen germination rates being lower than that of a hexaploid ‘Zenjimaru’, but more than equal to that of ‘Akagaki’. Although a much higher rate of fruit set was observed with pollinated ‘Fuyu’ than non-pollinated ones, the fruit set rate was lower after pollination with pollen from nonaploid plants (nonaploid pollination) than from hexaploid plants (hexaploid pollination). Seeds from nonaploid pollination grew as well as those from hexaploid pollination until 44 days after full bloom. However, the growth of the seeds from nonaploid pollination slowed down and finally stopped, resulting in about two thirds of the final size of seeds from hexaploid pollination. In terms of the fruit weight, sugar content, and skin color, fruit from nonaploid pollination was almost indistinguishable from that from hexaploid pollination, while flesh firmness was lower with nonaploid than hexaploid pollination.
In order to produce green asparagus (Asparagus officinalis L.) spears in November by forcing culture in the Ohotsuku region of Hokkaido, the effect of the timing of digging up one-year-old rootstock on the spear yield was examined in 2010 and 2011. In this study, one-year-old rootstocks of ‘UC157’ grown in the field were dug up in early, middle, and late October in both years. There were no significant differences between the three digging times in the fresh weight of rootstock or soluble solid content (Brix%) in storage roots, although the fresh weight varied between the two years. On the other hand, significant differences in spear yield from one-year-old rootstock in the forcing culture bed were seen between the three digging times. Both the marketable and total spear yields were much higher with late October digging than with the other digging times throughout this experiment. Especially, the marketable yield from late October in 2010 was more than three times as high as that from early and middle October. These results suggest that the differences in spear yield between the three digging times might be attributed to the bud dormancy in one-year-old rootstock, and the high spear yield in late October digging implies that the release of bud dormancy might occur before late October. The cumulative hours of chilling exposure to an air temperature below 5°C for one-year-rootstocks of ‘UC157’ up to late October was 110 hours in 2010 and 130 hours in 2011. Since the harvest with late October digging started in middle November in both years, forcing culture in the Ohotsuku region of Hokkaido may make the domestic production of green asparagus in November possible in a short time.
We investigated the relationships of weight and soluble solid contents (SSC) of fruit and the bearing positions, time of flowering, and growing period of the fruit within the same ‘Benishimizu’ peach trees for three years (2007, 2008, and 2009). The fruit weight was high in the middle part of the main stem in 2007 and in the apical part of the main stem in 2008 and 2009. Weights of late-flowered fruit were significantly higher than those of early-flowered fruit in 2007, but there was no significant difference in the fruit weight among flowering dates in 2008 and 2009. As the fruit growing period from flowering to harvest increased, the fruit weight decreased in 2007 and 2008. On the other hand, SSC was higher in the apical part than in the middle and basal parts of the main stem in all the years. Also, in all the years late-flowered fruit showed a higher SSC compared to early-flowered fruit. The percentage of fruit with a high SSC (more than 15% Brix) was greater in fruit with a shorter growing period, while the fruit with a longer growing period had higher rate of low SSC (less than 10% Brix). Based on the above results, we concluded that the fruit weight is affected by the bearing positions of the canopy, and the SSC is affected by not only the bearing positions of the canopy, but also the time of flowering and the growing period of fruit.
We investigated the effects of end-of-day (EOD)-heating treatment on the growth and flowering of spray-type Chrysanthemum in a low growth-temperature environment. With a controlled 12-hour day length at 16/8°C (light/dark period), we found in the spray-type chrysanthemum ‘Sei-Roza’ that the EOD-heating treatment accelerated flower initiation and early flower bud development. With the objective of reducing energy use in greenhouses in winter, we investigated the effects of short-term heating when the lowest night temperature was lower than 18°C. As a result, when the night temperature was 13°C, the effects of 3-hour 20°C EOD-heating treatment led to about the same timing of flowering as a night temperature of 18°C for the three cultivars we examined (‘Sei-Roza’, ‘Monalisa’, and ‘Wodka Sunny’). We investigated the effects of EOD-heating treatment when the lowest night temperature was 13°C on the characters of flower clusters, which can be a problem for marketing. As a result, deformation of the flower cluster by a low growth-temperature was improved by EOD-heating treatment when we examined four cultivars (‘Sei-Roza’, ‘Sei-Elza’, ‘Monalisa’, and ‘Wodka Sunny’). In this case, heat consumption is reduced by about 15% according to our calculation. From these results, we have successfully shown that EOD-heating treatment is an effective temperature control technique.
In this study, we attempted to identify the maturity index of fruit for high aroma components of processed Japanese apricot liqueur (ume liqueur) of ‘Nanko’ Japanese apricot (Prunus mume Sieb. et Zucc.). Aroma components, total decalactone, ethyl butyrate, and butyl acetate, in ume liqueur were significantly related to the skin color b* value and fruit firmness of raw material fruit. The ume liqueur made from fruit which showed below 34.5 in the skin color b* value of raw material fruit contained each aroma component below 50 μg·L−1 in 2008 and below 100 μg·L−1 in 2009. The ume liqueur made from fruit with above 0.98 kg in fruit firmness of raw material fruit contained each aroma component below 50 mg·L−1 except for one sample in 2008, and below 100 μg·L−1 in 2009. The ume liqueur made from the fruit that showed an above 34.5 skin color b* value and below 0.98 kg fruit firmness value had significantly higher levels of total decalactone, ethyl butyrate, and butyl acetate than the other ume liqueur. Even though the ume liqueur was made from fruit stored within six days at 20°C, the skin color b* value and fruit firmness of raw material fruit were significantly related to the content of aroma components in ume liqueur. These results suggested that the skin color b* value and fruit firmness were available as indexes of aroma components in the ume liqueur made from ‘Nanko’.
The effects of pinching and lowering on cucumber yield and yield components were investigated. A short-term experiment was conducted on 3 cucumber (Cucumis sativus L.) cultivars grown hydroponically in a greenhouse from July to October 2011. Pinching plants were pinched at above 20 leaves on a main branch and at the 2nd leaf on the first lateral branches. Lowering plants were pinched at above 15–19 leaves on a main branch and not pinched on 4 lateral branches that were lowered with their growth. The fresh fruit yield of pinching plants in all cultivars was higher than in lowering plants. The high fresh fruit yield was caused by the high dry weight yield, and the high dry weight yield was caused by the high dry matter production and distribution of it to fruits. Total dry matter production was correlated with light interception at 40 days after transplanting, but was correlated with light use efficiency, i.e., dry matter production per intercepted light, during the entire experimental period.
For the purpose of reducing heating costs, a basal stem heating system was developed using a heat duct at the ground parts of the plants in a plastic tunnel on the forcing culture of eggplant. The basal stem temperature under the heating system in the night was markedly (6.3°C) higher than that of the control, and the air temperature in the plastic tunnel was 3°C higher than that of the control even under the non-heating condition. The basal stem heating system accelerated the growth of the lateral shoots and fruit, and the number of harvested fruits and marketable fruit yields under the heating system were higher than those under the control. The marketable fruit yield under the heating system in the plastic house at 10°C was similar to that under the control at 12°C. Setting up the basal stem heating system was not costly (20,000 yen·10a−1) since the heating system can be prepared using existing heating machines. It is, therefore, suggested that a basal stem heating system with a plastic tunnel and branch duct is a useful and practical method for reducing the cost of the forcing culture of eggplant.
Oriental hybrid lilies show low cut flower quality, such as a shortened stem length and cleaved flowers, in high-temperature seasons. To achieve stable cut lily flower production in summer, the night temperature of a greenhouse was controlled using a heat-pump system. Bulbs of ‘Siberia’ lily were planted in two greenhouses with and without night temperature control in August. When the greenhouses were cooled during the night, the air temperature during the day and soil temperature also dropped. Plants grown in a greenhouse controlled at 19–22°C during the night showed flowers with a longer stem and lower frequency of cleaved flowers compared with those in a greenhouse with an ambient temperature. When night cooling was performed only 3–4 weeks after planting in early August, the plants produced longer stems similarly to those grown under cool night temperature conditions until flowering. No difference in the bulb dry weight was observed regardless of the night temperature. Increased dry weights were observed in the stem, leaf, flower buds, and especially stem roots of plants grown under cool night temperature conditions compared with plants grown under ambient temperature conditions. The vigorous growth of lilies under cool night temperature conditions is due to the development of stem roots that provide adequate water and nutrient absorption.
Commercial fruit dendrometers allow the precise measurement of the growth in diameter of hard fruits such as apple but not soft fruits, such as strawberry. In this study, a dendrometer was improved to monitor the longitudinal diameter of strawberry fruit to clarify its diurnal changes. A rubber-edged slit was prepared at the center of the hind frame to fix the strawberry fruit safely. A vertical compression spring with a spring constant of 0.049 N·mm−1 was added to the front plate, and it proved effective for measuring the growth of strawberry fruit. Moreover, the height of an original point was reduced by about 1 mm and it was found to be useful for the precise measurement of fruit growth. Longitudinal diameters of strawberry fruit were measured in various harvesting periods and maturity stages. In addition, measurements were also conducted under different weather and humidity conditions. The results showed that the improved dendrometer could precisely monitor the longitudinal diameter of strawberry fruit for its diurnal changes and the effects of environmental stresses on the fruit growth.
We investigated the effects of short-term heat treatment during the dark period on early growth and flower initiation and development in African marigold (Tagetes erecta L.). Under a controlled cycle of a 12-h day length at 22°C/14°C (light/dark), the effects of heat treatment at 30°C for 3 h were tested at different time points during the dark period. We found that flower initiation and early flower bud development were accelerated at the beginning of the dark period, while early growth and flower bud development after flower budding were accelerated by heat treatment in both phases (end of day and end of night) of the dark period. Thus, with the analogy of end-of-day FR, we propose end-of-day heating, which involves short-term heat treatment at the beginning of the dark period, for accelerating flowering.
The starch content of the cotyledon and vascular bundle development during nut growth were examined in Japanese chestnut (Castanea crenata Sieb. et Zucc.). The approximately linear increase observed in the fresh weight of the cotyledon from the end of July until harvest was closely related to the increase in the starch content of the cotyledon. The starch, which accumulated from around the inside of the cell to its center, was initially detected at the beginning of cotyledon growth. The subsequent deposition of starch in ‘Tanzawa’ occurred approximately one month before it did in ‘Tsukuba’. The maximum starch content (% on dry weight basis) was observed in mid-August in ‘Tanzawa’ and in mid-September in ‘Tsukuba’. With respect to the transport and accumulation of carbohydrates in the cotyledon, the development of extensive vascular bundle connections between the seed coat and central axis during the growth of the cotyledon suggests that carbohydrate transport into the cotyledon cells could be derived from these vascular bundles. Based on the developmental stage during which starch accumulation occurs, tree management from an early period of nut growth may be important for starch accumulation in the cotyledon.
It was reported that the incidence of fruit cracking decreased with twisting of the peduncle in tomato. However, the detailed process in the peduncle was unclear after physiological treatment. In this study, we observed morphological changes in the peduncle during tomato fruit development after physiological treatment. One day after treatment, the secondary xylem detached from the cambium, the inner space expanded in the pith and cortex, and cell arrangement was disordered in the cambium. Three days after treatment, a thin cell wall was newly observed around the phloem, and callus tissue with meristic cells was formed around the inner phloem and cambium. Hypertrophic cells appeared in a detached region near the cambium. Five to nine days after treatment, wound vessels, wound phloem, and new cambium differentiated and spread in the callus, and connected with the vascular system of the normal region in the peduncle. From these observations, it was suggested that the pathway of vascular bundles was destroyed with physiological treatment, but a new connection of vascular bundles with callus formation was constructed again, and the supply system conveying nutrients for fruit development was reorganized.
Cut flowers are usually cut under water to facilitate rehydration by Japanese flower retailers. This procedure, cutting stems under water, is laborious for retailers. Based on questionnaires, cutting stems under water was found to be practiced by 62% of retailers, and 72% of retailers believed that cutting under water is effective in facilitating the rehydration of cut flowers. Next, we investigated whether cutting under water is effective in facilitating rehydration using cut chrysanthemum, rose, lily, lisianthus, gerbera, alstroemeria, and stock flowers that had been dried. In chrysanthemum and gerbera flowers, an increase in the fresh weight of the cut flowers was accelerated by cutting stems under water, but it was not in the other cut flowers. There were no significant differences in the vase life of all cut flowers between cutting under water and cutting in air. These findings suggest that the effect of cutting stems under water on the rehydration and vase life of cut flowers is limited.