Research for Tropical Agriculture
Online ISSN : 2187-2414
Print ISSN : 1882-8434
ISSN-L : 1882-8434
Volume 12 , Issue 1
Showing 1-12 articles out of 12 articles from the selected issue
Original Article
  • Hiroshi MATSUDA, Aoi KITAMURA, Hirokazu HIGUCHI
    2019 Volume 12 Issue 1 Pages 1-7
    Published: 2019
    Released: March 07, 2020
    JOURNALS FREE ACCESS

    Six lychee cultivars (‘Bengal’, ‘Chakrapat’, ‘Kwai May Pink’, ‘Pot Po Heung’, ‘Souey Tung’, and ‘Tai So’) were cultivated under greenhouse condition in Kyoto, Japan. Hand-pollination was conducted, and the harvested fruit quality and productivity were determined in 2014 and 2015. Seed morphology was tested and the fruits were divided into three groups accordingly: normal, chicken-tongue, and rudimentary-seed fruits. The highest incidence of chicken-tongue seed fruits was found in ‘Pot Po Heung’ (≈50%), and lowest (10–20%) was in ‘Kwai May Pink’. A rudimentary seed was found only in ‘Chakrapat’ fruit, and the incidence was 35–50%. Peel color red was best in ‘Bengal’. Cultivar of the largest fruit was ‘Chakrapat’ (34–36g) when the seed was normal, followed by ‘Bengal’ (31–33g). The smallest fruit (≈20g) was ‘Pot Po Heung’. Fruit weight of chicken-tongue seed was largest (≈25g) in ‘Bengal’, and smallest (≈15g) in ‘Souey Tung’. Rudimentary-seed fruit of ‘Chakrapat’ was the smallest (13–15g) of all the categories above. Edible portion was largest in ‘Kwai May Pink’ (74–82%), and smallest in ‘Bengal’ (65–76%) which contained largest seed. Total soluble solid content were lower in ‘Chakrapat’ and ‘Tai So’. Titratable acidity was lower in ‘Kwai May Pink’ and ‘Pot Po Heung’. Eating quality was highest in ‘Kwai May Pink’, followed by ‘Bengal’. Eating quality of ‘Chakrapat’ and ‘Tai So’ varied largely at low level. Difference in seed type did not affect eating quality. Productivity was highest in ‘Chakrapat’ and ‘Kwai May Pink’. ‘Kwai May Pink’ produced well with high quality on both years.

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  • Atsushi SHIMADA, Shigeto TOMINAGA, Masashi YAMAMOTO
    2019 Volume 12 Issue 1 Pages 8-15
    Published: 2019
    Released: March 07, 2020
    JOURNALS FREE ACCESS

    We used an infrared light shading net to lessen any high-temperature damage such as to the fruit quality in passion fruit. The effects of several shading levels on vine growth and fruit quality of passion fruit were investigated. Shading treatments lowered the air temperature and leaf-surface temperature. Under low shading (shading level of about 30%), there was no influence growth on but the highest sugar/acid ratio of juice was observed among all treatments. However, middle shading (shading level of about 40%) resulted in a shade-avoidance syndrome on the vine, which under heavy shading (shading level of about 60%), the leaves showed that shade leaf and flowering was inhibited. Furthermore, delay of the maturation of fruit, fruitlets, and low sugar/acid ratio of juice were observed, indicating that a shading level of about 30% was optimal for shading; increasing the photosynthetic rate and improving the fruit quality of passion fruit.

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  • Hiroo TAKARAGAWA, Masami UENO, Yoshinobu KAWAMITSU
    2019 Volume 12 Issue 1 Pages 16-22
    Published: 2019
    Released: March 07, 2020
    JOURNALS FREE ACCESS

    Effective utilization and maintenance of sugarcane varieties are important for realizing sustainable, stable and high production. In this research, we collected statistical data and conducted questionnaire survey to clarify usage situation after release of the varieties. On the composition of varieties, there are many areas with more than 30% of one specific variety. Especially in Kumejima, Miyakojima, Tanegashima and Yoronto, where the risk of disease spread is higher due to higher ratio of ratoon area, diversification of used variety is required. In the southern part of the mainland Okinawa, Minami- and Kita-daitojima, Iheyajima, Amamioshima, Kikaijima, and Yoronto, the proportion of “other varieties” is as high as 20 to 40%, which is due to use of un-recommended varieties and mixed varieties. In addition, the questionnaire survey revealed that the benefits of utilizing multiple varieties, such as suitable varieties and risk diversification, are recognized. On the other hand, there are many problems of multiple varieties such as mixed varieties, complicated pulling seedling and seedling management, and too much number of varieties to select. Regarding mixed varieties, complementary planting for missing plant is considered to be a main reason, and it can be solved by enhancing planned seedling field and seedling beds for raising. In addition, it is necessary to print a handbook that both producers and extension stuffs can utilize and support efficient variety selection and composition without bias.

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  • Haruyuki DAN, Yoko OKI, Shinji HIROUCHI
    2019 Volume 12 Issue 1 Pages 23-30
    Published: 2019
    Released: March 07, 2020
    JOURNALS FREE ACCESS

    In the light of an increasing population growth in Ghana, it is urgently necessary to improve the rice yield by controlling weeds, recognized as a factor constraining rice production in the inland valleys of Ghana. At the irrigation facilities with cover plants, it is important to establish a maintenance technology for the introduced plants to prevent weed growth and to develop weed suppression technique which do not adversely affect rice growth when cover plants invade the paddy fields. Moreover, it is necessary to study the effects of conventional farming practices on cover plant growth. From this viewpoint, three experiments were implemented with three test plants that could be introduced as cover plants. By applying three herbicides already in use, glyphosate, propanil and butachlor, which are generally applied to the whole paddy field with mature weeds right before rice transplanting in the study area, the growth of test plants was suppressed. The same effect was observed with a quarter of the applicable herbicide quantity recommended by extension workers. We have confirmed that these test plants began to regrow one week after burning and so making annual replanting of test plants unnecessary. Burning saves labor-intensive weeding of invading plants, replanting test plants and cutlass slashing. Test plants survived under two months of flooding and regrew in four months after drainage. It was demonstrated that these plants could be completely eradicated by combining a glyphosate application and flooding for more than two weeks.

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Information
  • Koji UCHINO, Akiko HAMASHIMA, Koji IWATA, Hitoshi KUKITA, Osamu KUMAMO ...
    2019 Volume 12 Issue 1 Pages 31-35
    Published: 2019
    Released: March 07, 2020
    JOURNALS FREE ACCESS

    In Tarumizu, Kagoshima Prefecture, the lowest daily temperatures of -1.2°C and -6.3°C were recorded on December 18, 2015 and January 25, 2016, respectively. Some tropical and subtropical fruit trees suffered from the cold weather. In avocado ‘Pinkerton’, after the tree encountered a low temperature of -1.2°C, the flower buds, flower clusters and some leaves were browned. After encountering a low temperature of -6.3°C, the tree died. ‘Bacon’ and ‘Duke’ avocado cultivars did not receive the cold damage after encountering a low temperature of -1.2°C. However, after encountering a low temperature of -6.3°C, the flower buds, leaves and thin branches were browned and died. In both cultivars, new shoot extended and new leaves expanded in the spring. In litchi, after encountering a low temperature of -1.2°C, young leaves and a part of flower clusters were browned. After encountering a low temperature of -6.3°C, the tree died regardless of cultivars. Papaya did not receive the cold damage after encountering a low temperature of -1.2°C, but died after encountering a low temperature of -6.3°C regardless of cultivars.

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