Eighteen accessions of Lilium japonicum were collected in 12 prefectures of five regions of Japan. One hundred thirty-two bulblets of the accessions, which were prepared through tissue culture, were cultured in containers for five years. Though one (MHN) of the accessions from Wakayama Prefecture flowered in the first year, the difference of flowering ages did not correlate with the prefectures and/or regions. Six accessions from four southern prefectures, i.e., Miyazaki, Tokushima, Wakayama and Nara Prefectures, set many flowers in the fifth year of cultivation. However, the bulb weights were differed among the multiflorous accessions. One accession (KYY) from Nara Prefecture had a large bulb, whereas an accession (BNK) from Tokushima Prefecture had a small bulb. The weight of the bulbs after the fifth year correlated with the ratio of additional weight relative to initial weight in the first year of cultivation. Therefore, selection based on bulb growth will result in the loss of genetic resources among small bulbs for garden varieties.

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Flower-bud formation and dormancy breaking were investigated in three hybrid lily cultivars, ‘Morino-otome’, ‘Morino-sei’ and ‘Morino-roman’, developed by crossing Lilium × formolongi with L. rubellum. When these cultivars were grown in an unheated plastic house, daughter bulbs were formed before the flowering of mother plants. Flower-buds were formed in the daughter bulbs on November 1, two months later than in L. rebellum. The dormancy breaking of these three cultivars started on December 1, five months earlier than in L. rubellum. The mode of flower-bud formation in these three cultivars is comparable to that in L. rubellum, whereas their weak bulb dormancy is rather similar to that in L. × formolongi. When these three cultivars were grown at day/night temperatures of 20/16°C, flower-buds were formed in the daughter bulbs on August 1, and dormancy breaking occurred on November 1.

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‘Dingaras Multiple Purple’ (‘DMP’) was introduced from India and is resistant to bacterial wilt caused by Ralstonia solanacearum. To analyze the genes providing bacterial wilt-resistance in ‘DMP’, the F₁, F₂ and BC₁ (‘Mizu-nasu’/‘DMP’) groups were evaluated for bacterial wilt-resistance by bioassay methods using hydroponics with containers and bottles. Histograms of the death rate in F₂ group displayed a normal distribution. This suggested that the bacterial wilt-resistance in ‘DMP’ is polygenic. Since the death rate was not influenced by different cross combinations between ‘Mizu-nasu’ and ‘DMP’ in F₁ and F₂ groups, the main bacterial wilt-resistance in ‘DMP’ is in the nuclear gene.

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Differences in fruit malformation were studied in two tomato cultivars (Lycopersicon esculentum Mill.). The degree of fruit malformation of ‘Ogatafukuju’ was greater than that of ‘Kyokko’, when seedlings were exposed to low nighttime temperatures (10°C). Leaf number and stem length to the first truss in both cultivars decreased significantly on exposure to low temperature compared to those of the control. Locule numbers in both cultivars increased significantly on exposure to low temperature.
When both cultivars were cultured at low temperature, flower bud formed in ‘Ogatafukuju’ was more irregular and deformed than that in ‘Kyokko’, based on observation by SEM.

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The effects of daylength (elongating day length) and night-break (interrupting night), by lighting with a homolux lump, on the shoot and fruit growth of ‘Pione’ grapes which were grown to harvesting twice a year in a heated plastic house were examined. Experiments were conducted from August 21 to November 6 during the second growing season in 1995.
The effects of a 14-hour daylength, 16-hours daylength, and night-break for 2 hours from 11 p.m. were compared. However, the effect of the 14-hours daylength was not significantly different from the control, the strongest effect on the growth of ‘Pione’ grapes being obtained by a night-break for 2 hours. The number of leaves on the lateral shoots and the average berry weight were significantly increased by a night-break for 2 hours and a 16-hour daylength. The lignification of primary shoots was delayed by this treatment but ultinately occurred.
The effects of night-break for 2 hours from 8:00 p.m., from 11:00 p.m. and from 2:00 a.m. were compared. Each night-break treatment promoted lateral shoot and berry growth and delayed lignification of primary shoots. The strongest effect on the growth of ‘Pione'’ grapes was obtained by night-break from 11:00 p.m..

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Leaf distribution, light environmental condition and dry matter production of 3-year-old 7 columnar type apple strains on Marubakaido (Malus. prunifolia Bork. var. ringo Asami) and 6 normal type apple cultivars on M.9EMLA were examined. Vertical distribution of leaf area and relative photosynthetically active radiation in the canopies of 3 to 6-year-old 7 columnar type apple strains on Marubakaido and ‘Fuji’ on M.9EMLA were also compared. Total leaf area per 3-year-old trees of 7 columnar type strains and 6 normal type cultivars differed individually. Trees of 7 columnar type strains had greater leaf area index per planting space and average leaf area than those of 6 normal type cultivars. The internode length of 1-year-old shoots of 7 columnar type strains was shorter than that of 6 normal type cultivars. Three to 6-year-old trees of 7 columnar type strains showed worse light environmental conditions in the canopies than those of 6 normal type cultivars. It was considered that worse light environmental condition in the canopies of these 7 columnar type strains was due to its characteristically closer distribution of large leaves on the shoots. Total dry matter production per year of 7 columnar type strains was from 212 g to 743 g and that of 6 normal type cultivars was from 429 g to 812 g. It was inferred from these results that the dry matter production protential of columnar type strains would be worse than that of the normal type cultivars because the measured value of dry matter production was almost the same between columnar type strains and normal type cultivars even when the former were grafted onto vigorous Marubakaido rootstock and compared with the latter grafted on dwarfing M.9EMLA.

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The effects of exogenous gibberellin A₃ and gibberellin synthesis inhibitors on the flowering time of the Japanese iris were investigated in open fields. Foliar applications of GA₃ to the medium flowering cultivar ‘Chihayajo’ at a concentration of 250 ppm in mid-April forced the flowering of the first floret 4 days early. Uniconazole-P at a concentration of 25 ppm in early May delayed the flowering of the second floret by 7 days. Cultivar differences in the effects of GA₃ and uniconazole-P on the flowering time were observed. A very early flowering cultivar ‘Yatugatake’ showed no difference in the average flowering day treatment while the medium flowering cultivar ‘Chihayajo’ showed the largest difference. These results suggest that sensitivity to GA₃ differed depending on cultivar. Treatment with chlormequat-chloride was less effective in inhibiting scape elongation, while paclobutrazol and uniconazole-P were remarkably effective. However, the effect on flowering time did not always correspond with the inhibition of scape elongation. With 2000 ppm chlormequat-chloride treatment, the average flowering day of the second floret was delayed by 4 days compared with the control, similar to 500 ppm paclobutrazol treatment.

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Seedlings of many Elatum hybrids of Delphinium form rosettes when they are grown from late autumn to winter and this rosette formation causes serious problems of retarded bolting and malformed flower spikes. This study was conducted to determine the effects of the photoperiod on bolting and flowering in Elatum hybrids of Delphinium at different temperatures and to identify desirable methods for rosette prevention.
Bolting was greatly stimulated by exposing seedlings to a photoperiod longer than 18 hours at a daily minimum night temperature of 15°C. The stimulating effect of light break was less, similar to that of a 16-hour photoperiod. Under photoperiod of 15 hours, some seedlings remained not to bolt when the day time temperature was prevailing (average temperature of 20-30°C) and the night time temperature was kept at 20°C. Earlier bolting resulted in earlier flowering with a decreased number of leaves to the first floret and fewer florets.
These results suggest that exposing seedlings to a photoperiod longer than 18 hours before lowering the night time temperature to 20°C was effective in preventing them from forming rosettes in Delphinium forcing.

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The temperatures of the head leaves of cabbage in a field can be higher than the air temperature during the day due to solar radiation. The decrease in freezing tolerance by solar radiation was confirmed by shading the head leaves. Although the highest leaf temperature without shading was about 28°C during the day, the leaf temperature with shading was lower than the air temperature. Deacclimation of the cabbage was also reduced by shading. Shading (31% of full sun) with cover materials stretched horizontally above the ground for 6 days increased the freezing tolerance in comparison with non-shading. These results demonstrate that the head leaves of cabbage grown in winter are often exposed to high temperatures on sunny days, affecting the freezing tolerance of the cabbage. Short-term deacclimation of cabbage induced by high leaf temperatures in winter can be transiently controlled by shading.

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The effects of new nicotinic insecticides to control Citrus leafminer were examined at a Citrus orchard where satsuma mandarin ‘Aoshima Unshiu’ trees were grown under intentional alternate bearing systems. Among the insecticides, acetamiprid was more effective than imidacloprid in controlling Citrus leafminer when they were sprayed on trunk. The effective concentration was 1 to 2%. The effect of acetamiprid was enhanced by the addition of vinylacetate and diethylene glycol monoethyl ether. Acetamiprid was more effective when applied 10 days before summer pruning than when applied just after pruning. When injected into the soil, imidacloprid was more effective than acetamiprid. For a 10-year-old tree, imidacloprid at a rate of 0.5 g per tree, should be applied 10 days before pruning or on the pruning day. It seems that the effects of the insecticides persist for about 11 weeks after treatment. Compared to whole tree spraying, considerable labor will be saved, up to 65% in injection treatment, and up to 30% in trunk spraying.

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[in Japanese]

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