Tropical Agriculture and Development
Online ISSN : 1882-8469
Print ISSN : 1882-8450
ISSN-L : 1882-8450
63 巻 , 3 号
選択された号の論文の7件中1~7を表示しています
Original Article
  • Kay Khaing OO, Kiyoshi TORII, Ke-Sheng CHENG, Eiji NAWATA
    2019 年 63 巻 3 号 p. 93-104
    発行日: 2019年
    公開日: 2020/03/07
    ジャーナル フリー

    Nay Pyi Taw has experienced significant land use and land-cover changes since its becoming the capital city of Myanmar in 2005. Its area was once a greenfield site in the shrub land but new developments have been underway since 2005. Detecting land use/ land-cover (LULC) changes in the city and its vicinity and understanding the impact of such changes on the environment are of vital importance for city planning, not only for the evaluation of the past but also for future prospects. In this study, multispectral satellite remote sensing images acquired in 2000 and 2014 were used for the analysis of LULC changes in the Nay Pyi Taw area. The post-classification change detection method with LULC classes, namely agricultural land, natural vegetation, water, settlements/built-up and bare land, was applied in this study. From the results of the change detection, the changes of LULC in different categories were analyzed. The areas of settlements/built-up, water and bare land increased by 28,902 ha, 2,249 ha and 569 ha, respectively, whereas agricultural land and natural vegetation decreased by 9,929 ha and 21,790 ha, respectively. The increase in settlements/built-up land mainly came from the conversion of agricultural land (56%) and natural vegetation (44%) during the study period. The area of the water body increased due to the construction of new dams. The information on spatial pattern changes and statistics in LULC classes makes an invaluable contribution to appropriate decision-making in the development of a sustainable land management strategy for agriculture as well as urbanization.

  • Takashi SHINOHARA, Mizuki USUI, Ayaka SABANAI, Atsushi SANADA, Daizou ...
    2019 年 63 巻 3 号 p. 105-112
    発行日: 2019年
    公開日: 2020/03/07
    ジャーナル フリー

    To determine the possible relation of ethylene evolution from fruit to premature drop in passion fruit, morphological changes and cellulase activity at the abscission zone (AZ) of passion fruit with the occurrence of fruit drop, acidity of the juice, and ACC (1-aminocyclopropane-1-carboxylic acid) content were measured using the fruit treated with distilled water (DW) and ethephon (100ppm) at 40 days after pollination (DAP). More than 20% of fruits of DW treatment dropped prematurely when total organic acid content (TOAC) of the juice was over 4.0 g 100mL-1 at 65 DAP. A significant increase in ethylene evolution from fruit was observed at 65 DAP in DW treatment, which not only induced coloring of the pericarp and reducing acidity of the juice but also manipulated the increase in ACC content at AZ. This was also confirmed with the amplified results of ethephon treatment: an increase in cellulase activity at AZ was manipulated by ethylene evolution from fruit of ethephon treatment. It should be noted that in this study cellulase activity at AZ did not respond to ethylene evolution from fruit of DW treatment. There may be possibilities that other cell wall disassemble enzymes, rather than cellulase alone, are likely responsible for premature drop in passion fruit. Ethylene evolution from fruit triggered concerted increase in degrading enzymes’ activity at AZ faster than reduction of the juice acidity, which may cause premature drop in passion fruit.

  • Oliver CAASI, Chiharu HONGO, Andika SURYANINGSIH, Suryo WIYONO, Koki H ...
    2019 年 63 巻 3 号 p. 113-121
    発行日: 2019年
    公開日: 2020/03/07
    ジャーナル フリー

    Rice diseases cause significant yield losses in Asia, particularly in the tropical regions. A field assessment of their severities and incidences was conducted in Cianjur, West Java, Indonesia, to determine the relationships between bacterial leaf blight (BLB), the most common disease in the preliminary investigation, and other diseases in the region. Six sites with a total of 22 rice paddies were sampled wherein a total of 1,609 tillers were evaluated at the harvest stage. The Ciherang variety was the most common of the six varieties grown in these sites. BLB and narrow brown spot (NBS) were prevalent in all sites. Severe NBS incidence was positively correlated with severe BLB, suggesting that the two diseases might be associated with each other. BLB severity assessment at harvest revealed that the disease had an inverse correlation with tiller weight, but only a minor impact on the grain yield of rice. BLB had a higher negative correlation with the chlorophyll contents than other diseases, and thus, may indicate the effect of the bacterial infection on leaves that had reduced their greenness.

  • Michel OUYABE, Hidehiko KIKUNO, Naoto TANAKA, Pachakkil BABIL, Hironob ...
    2019 年 63 巻 3 号 p. 122-130
    発行日: 2019年
    公開日: 2020/03/07
    ジャーナル フリー

    Plant internal environment harbors several microorganisms that exhibit beneficial effects to the growth, adaptability and productivity of their host plants. Diazotrophs are bacteria responsible for biological nitrogen fixation (BNF) in plants. Yam (Dioscorea spp.) is an important tuber crop for food security in West Africa, but also is the most neglected crop in term of research. This experiment evaluated endophytic nitrogen-fixing bacteria associated with water yam (D. alata) grown under different fertilizer regimes and the biological nitrogen fixation in non-fertilized plants through leaf δ15N. Pot experiment was conducted for 180 days and plants were treated with urea and cow manure. Nitrogen content in plant was increased under urea treatment. Nitrogen uptake was higher in urea as compared to non-treated plants. Leaf δ15N of control plants decreased over time from 60 days after planting (DAP) in all accessions and BNF ranged from 13% to 40%. At 180 DAP, 47 bacterial strains were identified at the species level grouped into three phyla. Proteobacteria represented 77% of total isolates and most isolates were from the roots. The predominant genera were Rhizobium, Mesorhizobium and Devosia. Using the culture-dependent method in this study, it was clear that fertilization practice affected the type and number of endophytic nitrogen-fixing bacteria associated with water yam. Twenty (20) to 32 % of isolated bacterial strains were specific to each treatment and only 8% were common to all treatments.

  • Michel OUYABE, Hidehiko KIKUNO, Naoto TANAKA, Pachakkil BABIL, Hironob ...
    2019 年 63 巻 3 号 p. 131-139
    発行日: 2019年
    公開日: 2020/03/07
    ジャーナル フリー

    Three accessions of lesser yam (Dioscorea esculenta L.) were grown under different fertilizer regimes in pots for 220 days at Miyako Island, Okinawa, Japan. Biological nitrogen fixation (BNF) was evaluated in non-fertilized plants. Nitrogen-fixing endophytic bacteria were isolated on nitrogen-free Modified Rennie medium at 180 days after planting (DAP). Results show that growth of lesser yam was affected by fertilizer regimes. Plant nitrogen content was increased under chemical fertilizer and organic matter treatments, while plant dry matter was not different among treatments at 180 DAP. Leaf δ15N decreased over time in control plants. BNF ranged from 20 to 65%, depending on accessions. The lowest value of %Ndfa was found in accession E-1 and the highest value was found in E-2 at 220 days after planting. 52 bacteria strains belonging to 17 genera and 36 species were isolated from root, stem, tuber and leaf. Surprisingly, most endophytic diazotrophic bacteria were isolated from the leaves and the stems (76%) in all accessions. Proteobacteria including bacterial genera such as Acinetobacter, Pantoea, Pseudomonas, Pseudomonas, Serratia and Stenotrophomonas were identified as well as Actinobacteria and Firmicutes (Bacillus and Paenibacillus). We report here, for the first time, different nitrogen-fixing bacteria isolated from tuber of lesser yam. Our study suggests, for the first time that lesser yam can obtain substantial amount of nitrogen from air in association with diazotrophic endophytic bacteria. This is to our knowledge the first report on estimation of BNF in lesser yam.

  • Momoko IWATA-HIGUCHI, Jun-Ichi SAKAGAMI, Sachio MARUYAMA
    2019 年 63 巻 3 号 p. 140-149
    発行日: 2019年
    公開日: 2020/03/07
    ジャーナル フリー

    Soil moisture stress is a major constraint of upland rice cultivation under rainfed conditions in Africa. The aim of this investigation was to clarify the effect of soil moisture stress at the panicle development stage on the growth and yield of New Rice for Africa (NERICA) cultivars. In 2012, five upland rice cultivars (NERICA 1 (N1), NERICA 4 (N4), NERICA 7 (N7), WAB56-104 and Yumenohatamochi) were grown in pots with application of soil moisture stress of -20 to -49 kPa for 20 days at panicle formation (PF) or booting (BT) stages. Similar soil moisture stress was imposed on the same cultivars, except WAB56-104, for 15 days at spikelet formation (SF) stage in 2013. Compared to the condition of adequate soil moisture, the number of spikelets and the grain yield of tested cultivars were reduced for application of soil moisture stress in PF, BT and SF. N1 showed less reduction of the number of spikelets than N4 or YHM for stress in BT. In addition, N1 had less decline in net assimilation rate, and tended to have higher increases in leaf nitrogen and chlorophyll contents than the other cultivars for stress in SF. These results suggest that N1 maintains higher net assimilation rate and larger number of spikelets under soil moisture stress applied at SF and BT, respectively, than the other NERICAs.

  • Momoko IWATA-HIGUCHI, Jun-Ichi SAKAGAMI, Sachio MARUYAMA
    2019 年 63 巻 3 号 p. 150-159
    発行日: 2019年
    公開日: 2020/03/07
    ジャーナル フリー

    The aim of this investigation was to clarify the effect of soil moisture stress at the panicle development stage on spikelet differentiation and degeneration of NERICA cultivars. In 2012, five upland rice cultivars (NERICA 1 (N1), NERICA 4 (N4), NERICA 7 (N7), WAB56-104 and Yumenohatamochi) were grown in pots with application of soil moisture stress of -20 to -49 kPa for 20 days at panicle formation (PF) or booting (BT) stages. Similar stress was imposed on these cultivars excluding WAB56-104 for 15 days at spikelet formation (SF) stage in 2013. The stress reduced the number of differentiated primary rachis branches (PB), secondary rachis branches (SB) and spikelets in PF and increased the number of degenerated PB, SB and spikelets in BT and SF. N4 had a larger number of differentiated spikelets on SB, N7 had a larger spikelet mass, and these cultivars had higher percentage of degenerated spikelets than N1 and Yumenohatamochi. N4 and N7 tended to have larger shoot dry weight (SDW) and non-structural carbohydrate (NSC), but greater decline in these parameters than N1 and Yumenohatamochi under moisture stress in SF. Furthermore, the number of surviving spikelets per SDW or NSC, defined as spikelet surviving efficiency, of N4 and N7 was relatively smaller than those of N1 and Yumenohatamochi. The results suggest that cultivar differences in spikelet degeneration under soil moisture stress are ascribed to carbohydrate availability and spikelet surviving efficiency, which reflects panicle structure and spikelet mass.

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