We examined the effect of UV-C irradiation on the reduction of decay caused by gray mold (Botrytis cinerea Persoon), as well as on the accumulation of scoparone, an important defensive secondary metabolite, in the flavedo (exocarp) of four different Citrus species. Fruits were inoculated with gray mold 4 days after UV-C irradiation. In irradiated Satsuma mandarin and Hyuganatsu fruits let to a delay of disease incidence, and the reduction of the decay radius in Satsuma mandarin, ‘Kiyomi’ tangor, and Hyuganatsu fruits. In contrast, control fruits of Satsuma mandarin, ‘Kiyomi’ tangor, and Hyuganatsu, which had been inoculated with gray mold but had not been subjected to irradiation, showed a pronounced fungal penetration at 7 days post-inoculation. The amount of scoparone accumulation in the inoculated flavedo varied among species and with the irradiation treatment. Scoparone accumulated more rapidly and reached higher levels in irradiated ‘Kiyomi’ tangor and Hyuganatsu than in the control fruits. Interestingly, the disease incidence in the irradiated ‘Eureka’ lemon fruits was considerably lower than that in the other species. However the average radius of decay in the lemon fruits showed no decease and the levels of scoparone were far lower in both irradiated and non-irradiated fruits. We concluded that UV-C irradiation enhanced the accumulation of scoparone and increased resistance to gray mold in the other three Citrus species. These findings contribute to the decrease of the post-harvest disease caused by the fungus in some Citrus species.

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This experiment studied the periodic changes in the growth of sago palm suckers with different generation orders from the mother palm in a clump. Those were suckers which directly generated from the rhizome base of the mother palm (S1), generated from the rhizome base of the S1 (S2), and generated from the rhizome base of the S2 (S3). Plant height and number of leaves at the start of measurement were higher in the order; S1>S2>S3. Two different treatments were employed in the clumps; those without (Plot I) and with (Plot II) maintenance practices. Those practices, such as manual weeding and cleaning the debris inside and surrounding the clumps, were only carried out for about one year. During early one year observation, no reduction in the survival rate was observed in Plot II but it reduced to 22% in Plot I. One year after the maintenances were stopped in Plot II, the survival rate of S1 remained unchanged but small reductions were observed in S2 and S3. At 45 months later, the average survival rates of S1, S2, and S3 from both Plots were 50%, 64%, and 34%, respectively. In Plot I, S3 increased their heights more rapidly compared to S2 and S1. These results were different from those in the Plot II where all measured suckers showed similar growth. In both Plots, the production of newly-expanded leaves of S1 was faster than those of S2 and S3 while S2 and S3 produced similar numbers

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Pre-anthesis flowers were detached from cherimoya trees and incubated under various temperature/humidity (15–30ºC/40–90% relative humidity [RH]) combinations. The anthesis time was recorded and collected pollen was then subjected to hourly germination tests within 4 h after anthesis. Anthesis time was markedly influenced by temperature, but little by humidity. Flowers reached anthesis earliest (1400–1430 h in the afternoon) at 20ºC and at 25ºC. However, the time period in which anthesis was reached at 25ºC (1400–1500 h) varied more than that at 20ºC. Anthesis occurred 1 h later (1500–1600 h) at 15ºC, and variedly widely from 1400–1700 h at 30ºC. The germination percentage of collected pollen was influenced by pre-anthesis temperatures more than humidity. The germination percentage of the pollen collected just after anthesis was highest (> 90%) when the flower was incubated at 20ºC, and lowest (≈70%) at 30ºC. Germination tended to be low both at high temperature (30ºC) with high humidity (90% RH) and at low temperature (15ºC) with low humidity (40% RH). Pollen-tube elongation just after anthesis was not influenced by temperature or humidity. Thereafter, germination and pollen-tube elongation tended to decrease rapidly at higher temperatures and lower humidities. At high humidity (> 80% RH) at 15–20ºC, the germination percentage was maintained more than 70% for 4 h. Pollen-tube elongation at 3 h after anthesis was highest at 20ºC. The favorable temperature and humidity range was restrictive: around 20ºC with 80–90% RH.

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Using green manure plants is a common practice for crops in light-texture soil with low organic matter content. The effects of the application of crotalaria (Crotalaria spectabilis L.) and hairy vetch (Vicia villosa R.) green manure plants on the growth and yield of turmeric (Curcuma longa L.) were evaluated in dark-red soil in Okinawa, Japan. Dry green manure of crotalaria or hairy vetch was applied at the rate of 81.43-82.86 g per turmeric plant in field experiment. This rate provided 2.52-2.74 g N, 0.11-0.12 g P and 0.89-0.95 g K per turmeric plant. In glasshouse experiment, 250.00 g dry green manure of crotalaria or hairy vetch per turmeric plant was applied and the rate provided 7.62-8.43 g N, 0.33-0.36 g P and 2.70-2.91 g K. The manures maintained the soil pH at 6.5-7.0 and reduced the soil bulk density by 19%. In the field, turmeric yield (rhizome) increased by 7-10% with the application of green manure plants. In the glasshouse, shoots remained green 30 days longer, and plant height, tiller number, leaf dry matter content, shoot dry matter content and yield increased by 20, 76-165, 157-184, 173-197 and 28-86%, respectively, when turmeric was grown with the application of a 3-times higher amount of green manure plants, compared to that in the field experiments. Hairy vetch alone provided 46% higher yield, while crotalaria provided similar yield, compared to the fertilizer treatment. Curcumin concentration (%) in the rhizomes was lower by 4-54%, presumably due to the excessive amount of N supplied by the green manure plants and lower K nutrient content. The current study demonstrated that green manure plants provided nutrients and improved some of the physical and chemical properties of dark-red soil, which significantly enhanced the growth and yield of turmeric.

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Water yam (Dioscorea alata L.) are adaptable to cultivation under different soil conditions. This study aimed to reveal the effects on the growth of water yam under natural alkaline soil conditions (called Shimajiri Mahaji locally) at the Miyako Islands, Okinawa Prefecture in 2011 and under three fertilizer levels and varied pH in the greenhouse at Setagaya, Tokyo, Japan in 2012. The Shimajiri Mahaji soil for this experiment was of poor fertility with a pH of 7.9. The application of a larger quantity of fertilizer did not affect plant growth. The lack of effect of N: P: K fertilizer on the yield of ‘Okinawa white’ yam might have been due to the disturbance of mineral absorption by the alkaline soil conditions. The effect of alkaline soil conditions (pH 8.0) on the growth of five water yam cultivars including ‘Okinawa white’ was investigated at Tokyo, Japan. Plant growth varied among cultivars under alkaline soil conditions, in which some cultivars grew well. No Fe or Mn deficiency symptoms were observed on any tested cultivars under alkaline soil condition. The dry weights of tops and roots of ‘Okinawa white’ were smaller compared to control in alkaline soil, but the dry weight of tubers was not significantly different. Water yam could adapt to alkaline soil conditions, depending on the cultivar. Thus, different fertilization guidelines for the cultivation of adaptable cultivars of water yam on alkaline soils such as Shimajiri Mahaji should be developed.

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