This study investigated the effects of the growth chamber temperature on the germination and growth of Eustoma grandiflorum after the wet treatment of seeds at 10°C. When the dark-period temperature was 18°C, the germination rates for seeds under light-period temperatures of 22.5 and 25°C were slower than those under a light-period temperature of 30°C. The final germination rate for seeds with a light period at 35°C was significantly lower than those under the other conditions. With the light period at 32.5°C, the numbers of days to bolting, flower budding, and flowering were significantly higher than those at 27.5 or 30°C. When the dark-period temperature was 18°C, the rate and percentage of germination with a light-period temperature of 27.5°C were the same or lower than with a light period temperature at 30°C; however, when the dark-period temperature was set at 26°C, the rate and percentage of germination improved and were the same as with light/dark-period temperatures of 30/18°C. The leaf blade lengths of transplanted seedlings that had received light/dark-period temperatures of 27.5/26°C were significantly longer than those that had received light/dark-period temperatures of 30/18°C. Moreover, the numbers of days to bolting, flower budding, and flowering were significantly lower than in those with light/dark-period temperatures of 30/18°C. When the average temperature was 27.5°C, the germination rate was independent of the light/dark-period temperature under the four different conditions. However, the leaf blade lengths of the third true leaf at 32/14°C were shorter than those receiving the other three treatments. The leaf blade lengths of transplanted seedlings at 30/20°C were the same as those for 28/26°C and 27.5/27.5°C; however, the numbers of days to bolting, flower budding, and flowering at 30/20°C were significantly higher than those at 28/26°C or 27.5/27.5°C. We judged that the optimal light/dark-period temperature for producing Eustoma grandiflorum seedlings in the growth chamber was a constant 27.5°C, since changing the light/dark-period temperature requires complicated control.
The effect of nitrogen and potassium fertilization conditions combined with the local application (2–4 cm below the seeds) of calcium superphosphate on the bulb yield of direct-seeded onions (Allium cepa L.) was investigated. In addition, to clarify the effect of fertilization on the number of leaves during the growing period and the relationship with the number of leaves and yield, we investigated growth traits such as the early growth stage plant height and nutrient absorption in the bulb initiation stage, which may affect the number of leaves. Although the mechanism by which a fertilizer component applied before sowing, with the local application of calcium superphosphate, contributes to yield is still not completely understood, the results show that nitrogen and potassium application prior to the second leaf stage increases phosphate absorption and promotes nitrogen absorption in the bulb initiation stage. In addition, it leads to an increase in the number of leaves at the fall-over stage and the bulb weight per leaf. Moreover, this study shows that only applying calcium superphosphate locally does not increase the yield of ‘Okhotsk 222’, but that it requires combination with nitrogen and potassium application within the plow layer prior to the second leaf stage. This process promotes the absorption of nitrogen and phosphoric acid at the bulb initiation stage and contributes to an increase in bulb yield.
The effects of diurnal ventilation with a heat exchanger for dehumidifying were investigated to improve both the yield and quality of marketable tomato fruits grown in a greenhouse during winter. The heat exchanging ventilation based on the index of relative humidity lowered the temperature in the greenhouse. However, it ameliorated the inside conditions, such as decreasing humidity and reducing the period of dew condensation on the fruits. The concentration of carbon dioxide in the greenhouse remained higher than that of the control on cloudy days. Although the marketable yield from January to February decreased under the heat exchange ventilation, there was no significant difference in the total yield from January to May. In addition, the number of puffy fruits in March and April decreased, and total soluble solids from January to March were higher than those of tomato fruits cultivated in the control. Based on these results, it was revealed that tomato quality was improved compared with the control, while there was no significant difference in the total yield. Additionally it was suggested that the heat exchanging ventilation was effective as a dehumidifying technique for culture control.
Appropriate soil moisture is necessary for stable spinach production. We investigated the effect of water supply using Optimum Subsurface Irrigation System (OPSIS) with the aim of contributing to the development of a stable production technology for spinach. Our results confirmed that irrigation from multiple water supply lines allowed uniform spinach growth, irrespective of the plant position between water lines set 150 cm apart. The growth was promoted by underground irrigation through OPSIS, in comparison with above-ground water-spraying at the same soil pF value. The soil used for spinach cultivation in these experiments was an Andosol, for which the ideal soil pF value to start irrigation by OPSIS was 2.2. The amount of water for appropriate irrigation at this soil pF value was equivalent to 15 mm of rainfall on each occasion.
For the double cropping of cucumber in a greenhouse, alternating cultivation with soil and grow bags is more cost-effective than cultivation with only soil or grow bags. Therefore, to establish a cultivation method, coir grow bag cultivation was examined in the summer. As a result, stable growth and equal or high yield could be achieved, compared with those of soil cultivation, by placing a drainage pot that monitors drainage to optimize the supply of nutrient solution. In addition, no root-knot nematodes were found in grow bags placed on plastic mulch beds in a field markedly polluted with root-knot nematodes, with the larval density in the soil under the grow bags reduced to 1/17 during the cultivation. Furthermore, the nutrient supply was partially changed from nutrient solution to raw water to reduce the application of fertilizer, lowering the total emission of nitrate nitrogen in the soil to 8.5 g・m–2, demonstrating the high practicability of the coir grow bag cultivation in the summer.
The growth and yield of 12 different leaf lettuce (Lactuca sativa L.) cultivars were evaluated under different qualities of light produced by LEDs. Red leaf lettuce cultivars showed a tendency of increasing growth under a mixed light source of blue and red LEDs. On the other hand, in the case of green leaf lettuce cultivars, there was no clear difference in growth under different light qualities. Under lights including the blue spectrum, the stem elongations of all cultivars were suppressed compared with those irradiated by red LEDs. Based on those results, red and blue lights have antagonistic effects, promotion and suppression, respectively, on stem elongation of lettuce. Therefore, there was a difference in reaction characteristics due to LED light quality in each variety of lettuce.
Six varieties of sweet potatoes with different taste characteristics were tested to investigate the influence of the storage period on the respective amounts of components related to the taste of baked sweet potatoes. In addition, the taste of the sweet potatoes were quantified based on taste-related component amounts and the results of sensory evaluation. In the case of all six sweet potato varieties, enhancement of the sweetness of the baked sweet potatoes was largely due to storage-related increases in three sugar components: sucrose, glucose, and fructose. Further, in the case of the ‘Quick Sweet’ and ‘Beniharuka’ varieties, the maltose produced by baking markedly contributed to the enhancement of sweetness, in addition to the storage-related increase in the three sugar components. Differences in texture due to the storage period were caused, in the case of ‘Kokei 14’, mainly by the decomposition of starch during storage, and in the case of ‘Quick Sweet’ and ‘Beniharuka’, by a combination of this decomposition and baking. The degree of sweetness, obtained by multiplying each sugar content by the sweetness ratio and summing the results, had the highest correlation based on the results of sweet-taste sensory evaluation (r = 0.964**); and the starch content in dry matter showed the highest correlation with the results of texture-palatability sensory evaluation (r = 0.958**). Thus, the sweetness and texture could be respectively quantified based on the results of sensory evaluation related to the degree of sweetness and the starch content in dry matter.
The satsuma mandarin (Citrus unshiu Marcow.) is one of the most eaten domestic fruits in Japan, and it is rich in β-cryptoxanthin (β-CRX). Recent studies suggested that β-CRX has bone-health benefits. The satsuma mandarin produced in Mikkabi, Shizuoka Prefecture, was accepted for the first time among fresh agricultural products as a “Food with functional nutrient claims.” However, there are very few data concerning the differences among production areas and/or varieties in the β-CRX content and associations with fruit quality. In this study, we measured the β-CRX content of various kinds of this fruit harvested in major production centers and examined its relationship with the sugar content. As the results, we found that the cultivar with the lowest β-CRX content was gokuwase; the wase, nakate, and okute cultivars have similar levels of β-CRX. Furthermore, the β-CRX content is significantly and positively correlated with the sugar content in all production areas and varieties.
To force the blooming of cut Eustoma ‘Voyage (Type II) Blue’ flower stems harvested at the green-hued bud stage, we performed pulse or continuous treatment with 1% glucose and germicide solution with or without 1 mM methyl jasmonate (MeJA), in the presence or absence of light in autumn and spring. Both continuous and pulse treatments with MeJA led to a more uniform coloration of petals during flower opening. Pulse treatment with MeJA was effective for avoiding small petals and leaf injury. After pulse treatment with MeJA, light was necessary to improve petal pigmentation. MeJA was used to treat green-hued buds of six cultivars with yellow, green, lavender, white, and pink petals. In flower stems of the two white cultivars, pulse treatments with MeJA led to a more uniform coloration of petals. In other cultivars, nonuniform coloring was not observed irrespective of whether stems were treated with MeJA. MeJA and the control treatments led to similar flower diameters and color values. In addition, more than 50% of the cut flowers maintained their vase life for 10 days after flowering in both treatments. These results suggest that pulse treatment with MeJA is effective to force cut double-flowered Eustoma flower stems to bloom.
New ornamental peach cultivars with a pillar type tree shape and chrysanthemum-like flowers, ‘Hakurakuten’ and ‘Maihiten’, have been released from the collaborative investigation of ornamental peach breeding between Tokyo University of Agriculture and the Institute of Fruit Tree and Tea Science, NARO. Six hybrid trees were obtained from crosses between G-11-19, a seedling of ‘Houkimomo’ showing tree and flower traits very similar to those of the parent, and ‘Kikumomo’, showing a normal tree shape and flowers with double petals. F2 seedlings from self-pollinated F1 demonstrated segregation in tree shapes, flower types, and petal colors. The appearance rate of selections that have both traits was as low as 1.8%. In addition to the unique tree shape and flowers, ‘Hakurakuten’ has white petals, flowers 1 or 2 days earlier than ‘Kikumomo’, and has many flowers. ‘Maihiten’ has pink petals, flowers a few days earlier, and many flowers.
A new capsinoid-containing tasty pepper cultivar, ‘HC3-6-10-11’, was developed. ‘HC3-6-10-11’ is a purebred cultivar selected in the F8 generation from a hybrid cross between ‘Himo’, a capsinoid-containing tasty cultivar, and ‘CH-19 Sweet’ that contains many capsinoids and few capsaicinoids. After selections based on the fruit characteristics, we applied for variety registration in 2015, and obtained it in 2017. The average fruit weight of ‘HC3-6-10-11’ is ca. 6 g, and the yield is comparable with that of ‘Amato-bijin’ or ‘Sarada-amanaga’. Fruits harvested in 2014 contained 1,956 μg・g–1DW of capsinoids. A license system was established for growers in Nara Prefecture, who sell green immature fruits only to restaurants or processors.