Tropical Agriculture and Development
Online ISSN : 1882-8469
Print ISSN : 1882-8450
ISSN-L : 1882-8450
63 巻 , 4 号
選択された号の論文の9件中1~9を表示しています
Original Article
  • Katsuyoshi SHIMIZU, Hiroki ASAOKA, Megumi SASAKI, Naoto ISHIKAWA, Weid ...
    2019 年 63 巻 4 号 p. 161-166
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    In the present study, attempts were made to analyze the response of the germination percentage and growth of Egyptian wheat varieties (Triticum aestivum L. var. Bany-swif 1, Bany-swif 5, Sakha 93, Sids 1, Sohag 3, Giza 168) and Norin 61 to saline conditions. Germination percentages were every day up to 10 days. treatments were, temperature treatment: 5, 10, 20, 25and 30℃ under 24h darkness, salinity treatment: 0, 100, 200, 300 and 400 mM of NaCl,KCl or Na2SO4 at 25℃, and osmotic stress treatment: 0, 100, 200, 300 and 400mM of PEG. As a result, the germination percentages of wheat exceeded 90% at 10, 15, 20, 25, and 30 ℃ but low at 5 ℃. Sakha 93, Sids 1 and Giza 168 showed higher germination percentages under 400 mM NaCl and KCl, while Sakha 93, Sids 1, Giza 168 and Norin 61 showed higher germination percentages under 400 mM Na2SO4. No seeds could germinate under 300 and 400 mM PEG. It was estimated that SO42- and Na+ increased germination percentage, while K+ or Cl- inhibited it. Wheat was cultivated with salt treatment solutions (0, 51.3, 12.6 and 170.9 mM NaCl). The Egyptian varieties showed higher plant lengths than the Japanese one, Norin 61, at harvest time. Panicle weights tended to be higher under the 51.3mM NaCl treatment in the Egyptian varieties. As a result, it was estimated that those varieties had salt tolerance mechanisms and Na+ or Cl- under low salinity conditions might be a positive influence on their growth.

  • Shuichi MIYAGAWA, Akiko MATSUDA, Mizuki WATANABE
    2019 年 63 巻 4 号 p. 167-175
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    The present study aimed to elucidate changes in the type, utility, and production of crops and other useful plants (that support the livelihood of farmers), grown in the home gardens of a typical rainfed rice-growing village in Northeast Thailand during 1983, 2000–2001, and 2014–2015. The frequency (%) and coverage (%) of the plants were recorded in each home garden, and information about these gardens was collected through interviews with farmers involved. A total of 157, 137, and 102 plant species was recorded during the study periods, during which some plants were abandoned, and new ones were introduced as new income sources. Based on frequency and/or coverage data, the dominant crop in 1983 was chili (Capsicum spp.), which was an important income source for most households at that time. Subsequently, farmers added sweet basil (Ocimum basilicum) to their gardens in the 2000s and Chinese celery (Apium graveolens var. dulce) in the 2010s. During 2014–2015, no crop showed as high a frequency as chili in 1983, and the average coverage of Chinese celery was the highest among the crops, when it was planted in fewer gardens than chili and sweet basil. Chinese celery was grown using more inputs, such as termite-mound soil, thus earning more income than the other crops. When a specific crop was grown in a large area of the garden, the number of useful plant species was significantly smaller than that in the garden without such a crop after 2000. These changes may be associated with socio-economic ones in the village, as the number of households engaged in home-garden cropping as well as the importance of the home garden as a daily source of food and income have decreased during the last three decades.

  • Yu MON, Yoshinori YAMAMOTO, Mie Mie AUNG
    2019 年 63 巻 4 号 p. 176-185
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    In Myanmar, submerged and deep-water areas make up 13.5% of the total rice cultivation. The conditions here are unsuitable for seedling transplantation, and there is a locally-used method known as ‘cut-stem transplant’ (CST), a technique which allows rice production in the submerged and deep-water areas of Thanatpin Township, Bago Region. For this method, the rice stems are cut and transplanted using a fork-shaped tool. A survey was conducted in 2016 and 2017 to clarify the growth and yield of Pawsan and Yoesein varieties planted, with the CST technique in comparison with the same varieties grown using normal transplant and/or direct-seeded cultivation. The CST seedlings of the Pawsan variety produced tillers and roots from the lower elongated nodes within 3 days of transplantation, which developed into acropetal patterns. The second node produced a greater number of tillers and roots than other nodes. The harvest yield per m2 for this variety was the highest for the CST, followed by normal transplant and direct-seeded methods. Similarly, the grain yield per m2 of Yoesein CST was higher than those of direct-seeded methods. The grain yields per m2 in both varieties were most closely correlated with the number of grains per m2 for all rice cultivating methods except for the direct seeding of Yoesein in 2016. For the CST as well as other cultivation methods, the number of grains per m2 is strongly influenced by the number of panicles per m2. Therefore, to increase the rice yield when using CST, the cultivation methods for the varieties need to be manipulated so as to increase the number of panicles per m2 to ensure improved yields.

  • Keisuke FUJII, Hirokazu HIGUCHI
    2019 年 63 巻 4 号 p. 186-191
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    The saline-tolerant Bangladeshi soybean, AGS313, and the saline-sensitive Japanese soybean, Fukuyutaka, were cultivated under saline conditions to better understand the saline-tolerant mechanism. Plants in the vegetative stage were subjected to a 50 mM saline treatment for 3 weeks. Physiological responses, including photosynthetic and transpiration reactions, were measured in both soybean varieties. The accumulation of Na+, Cl-, K+, Ca2+, and Mg2+ was also measured in upper and lower leaves, upper and lower stems, and in the roots. The physiological responses of AGS313 were little affected by saline treatment, but those of Fukuyutaka were markedly decreased. The two varieties accumulated Na+ in their lower stems to a similar extent, and both controlled Na+ accumulation in the leaves. Soybean reportedly accumulates Na+ in its roots, but we found that lower stems had the largest Na+ accumulations. The similar Na+ accumulation patterns of the two varieties suggest that saline tolerance in AGS313 was not related to its pattern of Na+ distribution. However, while the saline-sensitive Fukuyutaka accumulated Cl- in its leaves under saline stress, AGS313 did not. These results suggest that AGS313 achieves saline tolerance by reducing Cl- accumulation in its leaves.

  • Makoto UENO, Tomoko TAMURA, Yuka YANO, Michihiro ITO, Naoya SHINZATO
    2019 年 63 巻 4 号 p. 192-197
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    We previously reported on the construction of a microbial library isolated from soils in Okinawa (Okinawa Microbial Library, OML, http://omlus.jimdo.com/), including the Yaeyama Archipelago, and validated its phylogenetic diversity. In the present study, we report that strain 5-94, obtained from soil samples collected from Ikei Island, Okinawa Prefecture, Japan, produced inhibitory compounds against Colletotrichum orbiculare, the causal agent of anthracnose disease. Mycelial growth of C. orbiculare was inhibited by strain 5-94 in a dual culture assay. Additionally, the use of culture filtrates of this strain significantly suppressed the spore germination in C. orbicular. The sequence analysis of the 16S rDNA region indicated that strain 5-94 was similar to the Streptomyces species. Anthracnose disease caused by C. orbiculare was suppressed by the strain 5-94 culture filtrate in cucumber leaves pretreated for 3 and 7 d. Furthermore, growth inhibition zones of C. orbicular in the culture filtrate of this strain were detected by a thin layer chromatography. These results, therefore, suggested that inhibitory compounds from the culture filtrate of Streptomyces strain 5-94 might be a promising source for the development of new chemical fungicides to prevent anthracnose disease caused by C. orbiculare.

  • Kanako TAKADA, Naoto TANAKA, Hidehiko KIKUNO, Pachakkil BABIL, Michio ...
    2019 年 63 巻 4 号 p. 198-203
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    The results of our previous experiment showed that water yam (Dioscorea alata L.) was able to grow under low fertility soil conditions without nitrogen fertilization. Moreover, changing δ15N values suggested that nitrogen is absorbed from the air. The objective of this study, therefor, was to confirm and identify the nitrogen-fixing bacteria in water yam plants. The nitrogen fixation ability of isolated bacteria was measured using the acetylene reduction assay in semi-solid nitrogen free medium. Phylogenetic analysis of 16S rRNA gene sequences revealed nine genera in the stems and roots. These isolates were shown to be related to genus Bacillus, Cohnella, Rhizobium, Kosakonia, Azospirillum, Pantoea, Dyella, Enterobacter, and Ralstonia. This is the first result that NFB were isolated from water yam plant cultivated under low soil fertility condition at Miyako Island, Japan.

  • Ittetsu YAMAGA, Shigekazu NAKAMURA
    2019 年 63 巻 4 号 p. 204-209
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    We studied the use of ultraviolet (UV-C) irradiation to suppress blue mold and promote accumulation of scoparone, which is associated with decay resistance in satsuma mandarin (Citrus unshiu Marc.) ‘Aoshima unshu’ fruit. UV-C irradiation (3.6 kJ∙m-2 and 6.0 kJ∙m-2) at 24 h prior to inoculation of fruits with blue mold reduced the incidence of soft rot and sporulation at 4 days after inoculation. Further, UV-C irradiation at 6.0 kJ∙m-2 reduced mycelium and sporulation areas at 4 and 5 days after inoculation. Concomitantly, UV-C irradiation at 6.0 kJ∙m-2 induced the accumulation of scoparone in flavedo tissue (98.8 μg∙g-1 FW) at 8 days after irradiation, and even at 20 days after irradiation, the concentration of scoparone was 87.8 μg∙g-1 FW. Finally, using uninoculated fruits, we tested the efficacy of UV-C irradiation for control of fruit decay caused by naturally occurring infections. Total disease incidence of blue and green molds under UV-C treatment was lower than that in controls at 8 and 17 days after irradiation. In the latter case, total disease incidence of blue and green molds among controls was 27.1%—about twice the incidence observed under UV-C treatment. This indicated that UV-C irradiation induced the production of scoparone as a defensive measure against fungal development in the flavedo tissue of satsuma mandarin fruits, while UV-C at 6.0 kJ∙m-2 effectively suppressed the rate of decay caused by natural fungal infections.

  • Kea KONG, Yoichiro KATO, Sarom MEN, Vang SENG, Akira YAMAUCHI, Mayumi ...
    2019 年 63 巻 4 号 p. 210-218
    発行日: 2019年
    公開日: 2020/09/09
    ジャーナル フリー

    On-farm experiments were conducted to determine the economic efficiency of fertilizer management and the optimal rate of fertilizer application for rainfed lowland rice (Oryza sativa L.) cultivation on Prateah Lang (sandy) soil in southern Cambodia. Five trials were conducted at different locations in 2013 and 2014. Each trial had six treatments of different nitrogen (N)-phosphorus (P2O5)-potassium (K2O) rates with three replicates in 2013 and four replicates in 2014. The amounts of P2O5 and K2O applied differed between the trials, although P2O5 and K2O application rates were the same between the treatments in each trial. The results demonstrated that the application of 60 kg ha-1 of N, 30 kg ha-1 of P2O5, and 15 kg ha-1 of K2O, whose cost was the second lowest (97.8 US$ ha-1) among those for 25 different N-P2O5-K2O rates, was the most profitable, suggesting that the N-P2O5-K2O rate of 60-30-15 is the best application rate at the experimental sites. While the grain yield increased with a higher fertilizer rate, the optimum rate to maximize income was achieved at a rather low fertilizer rate; hence, the fertilizer cost should be considered before determining the best fertilizer management strategy.

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