Tropical Agriculture and Development
Online ISSN : 1882-8469
Print ISSN : 1882-8450
ISSN-L : 1882-8450
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Original Article
  • Atsushi SHIMADA, Kaoru KURAMOTO, Byoung-Jae PARK, Fumio HASHIMOTO, Mas ...
    2020 Volume 64 Issue 2 Pages 47-53
    Published: 2020
    Released: July 02, 2020
    JOURNALS FREE ACCESS

    The optimum temperature during fruit ripening period of passion fruit (Passiflora edulis) was elucidated in the present study. ‘Summer Queen’ (P. edulis × P. edulis f. flavicarpa) and ‘Ruby Star’ (P. edulis × P. edulis f. flavicarpa) showed a greenish fruit peel and low total soluble solids/titratable acidity (TSS/TA) ratio at 15°C. In ‘Summer Queen’, a high °Brix, low titratable acidity, and high TSS/TA ratio were observed at 25°C. In ‘Ruby Star’, the peel coloration was highly favorable at 25°C. In both cultivars, the peel tended to be yellowish and °Brix of the juice was low at 35°C. These results indicate that the optimal temperature for passion fruit ripening was 25°C. In addition, we elucidated the varietal differences in the ripening characteristics of fruit on and off the vine.

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  • A Simulation Model to Estimate Number of Flowers
    Hiroshi MATSUDA, Hirokazu HIGUCHI
    2020 Volume 64 Issue 2 Pages 54-60
    Published: 2020
    Released: July 02, 2020
    JOURNALS FREE ACCESS

    Passion fruit plants were cultivated under greenhouse conditions in a warm-temperate zone to study the relationship between daily number of flowers (F) and cumulative hours (H) of a range of temperature regimes, and then the specific temperature regimes and the periods that affected F were determined. Multiple regression analysis with H as a variable was performed using stepwise backward elimination to develop a predictive model of F fluctuation. The F predictive model was then verified using F data collected from open orchards. The strongest correlations with H were detected at 15 days before anthesis (DBA). Significant positive and negative correlations with H<25°C and H>25°C, respectively, were detected during a period of several days around 15 DBA. Longer hours with temperatures <25°C increased F, whereas longer hours with temperatures >25°C decreased F. The strongest positive correlations were observed at H20–25°C, and the strongest negative correlations at H>30ºC. F decreased greatly when H>30ºC exceeded 6 h at 15 DBA, indicating that temperatures higher than 30°C severely affected F. F was not significantly correlated with H10–15ºC, nor H15–20ºC except for 19–21 DBA, indicating that the effect of temperatures <20°C on F was negligible. Within 1 week before anthesis, the effect of temperature on F was also negligible. Therefore, F fluctuation in passion fruit was accurately predicted about 2 weeks prior to flowering by the following equation for F as a function of H during 15 ± 3 DBA:

      F = b1H10–15ºC + b2H15–20ºC + b3H20–25ºC + b4H25–30ºC + b5H>30ºC,

    where b1 = 0.026, b2 = –0.0092, b3 = 0.013, b4 = 0.0066, and b5 = –0.012.

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  • Yoshinori YAMAMOTO, Kazuo KATAYAMA, Tetsushi YOSHIDA, Akira MIYAZAKI, ...
    2020 Volume 64 Issue 2 Pages 61-71
    Published: 2020
    Released: July 02, 2020
    JOURNALS FREE ACCESS

    Changes in leaf and trunk characteristics related to the starch yield with age of representative early- and late-flowering sago folk varieties, Rondo and Para, were compared around Lake Sentani near Japapura, Papua, Indonesia. Both folk varieties showed the same patterns of change in leaf and trunk characteristics, which were categorized into four and five patterns, respectively. The patterns for leaf growth are Type A: an increase until trunk formation (TF) after sucker emergence (SE) and then gradual decline (leaf length); Type B: an increase until TF after SE and then maintaining a definite value (stomatal density); Type C: an increase until TF after SE and then maintaining a definite value for some period of time, then a decrease after flower-bud formation (FBF) (number of leaflets; the longest leaflet; length, width and SPAD value; and leaflet area, leaf area, and leaf area per plant); and Type D: an increase until some trunk elongation after SE occurred and then maintaining a definite value (number of leaves and the longest leaflet thickness). Those for trunk growth are Type A: hardly a change after TF (trunk diameter); Type B: an increase until FBF after TF and then maintaining a definite value (trunk length, weight, and volume); Type C: a sharp increase over a certain period of time after TF and then maintaining a definite value until FBF (pith dry matter and starch percentage); Type D: a sharp decrease for a certain period of time after TF and then maintaining a definite value until FBF (pith total sugar percentage); and Type E: no clear change for some period of time after TF and an increase until FBF (pith starch content).

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  • Hiroo TAKARAGAWA, Hoang Thai DINH, Miki HORIE, Masami UENO, Yoshinobu ...
    2020 Volume 64 Issue 2 Pages 72-79
    Published: 2020
    Released: July 02, 2020
    JOURNALS FREE ACCESS

    Currently, the Mexican sunflower (Tithonia diversifolia) is an unexplored plant in Okinawa. Prior to establishing a manual for field cultivation, we examined the photosynthetic performance of plants grown at different nitrogen levels. Results showed that the photosynthetic ability of the plant was characterized by a higher light saturation point (1,200–1,800 μmol m-2 s-1), a higher initial slope of the A/Ci curve (0.17 mol m-2 s-1), a wide optimum temperature range (20°C–40°C), less photorespiration (14.9%–21.2%), a low correlation between the photosynthetic rate and stomatal conductance (r = 0.602, P < 0.01), and a polynomial relation of photosynthesis with specific leaf nitrogen (R2 = 0.786, P < 0.001). These results were consistent with the facts observed in the original habitat. Consequently, the present study provides the following information in cultivating the plant. First, the plant requires high levels of radiation and nitrogen, which impacts planting density and fertilizer application. Second, the plant exhibited lower stomatal responsiveness to changes in environmental factors, indicating that it required careful water management, which could represent a potential burden for its cultivation management.

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  • Khin Nilar SWE, Eiji NAWATA
    2020 Volume 64 Issue 2 Pages 80-89
    Published: 2020
    Released: July 02, 2020
    JOURNALS FREE ACCESS

    Despite the swidden agriculture still remains as a safety net for some ethnic minorities, the transformation into other agricultural practices have occurred, especially in Mainland Southeast Asia. Likewise, the agricultural activities of swidden agriculture in the Bago Mountains have gradually been in transition from the traditional swidden practices to permanent agriculture. In this study, recent trends of swidden agriculture and the introduced permanent agriculture were assessed by using not only satellite image assessment but also interviews and socioeconomic survey. The findings showed that the extent of swidden area gradually decreased after the introduction of the permanent agriculture in SN and KC village. Demise of swidden was found in GS village because of the advantage of low land availability. Land use conflicts, lowlander migration, labor and agricultural input availability were the major underlaying causes for agrarian transition. Although the newly introduced permanent agriculture may have significantly contributed to local livelihoods, more research must be conducted in order to find out the suitable agricultural land use for the future sustainability of siwddeners’ livelihood.

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  • Hiroshi MATSUDA, Tatsushi OGATA
    2020 Volume 64 Issue 2 Pages 90-96
    Published: 2020
    Released: July 02, 2020
    JOURNALS FREE ACCESS

    The thermal response of pollen germination and varietal differences in heat tolerance were examined in 14 passion fruit (Passiflora spp.) cultivars and varieties including 7 hybrid cultivars (P. edulis × P. edulis f. flavicarpa) and 2 different species. Pollen germination was tested on agar medium between 20°C and 42°C at 2°C increments. Thermal responses varied markedly among the hybrid cultivars. ‘Ruby Star’ and ‘Tai-nung #1’ pollen germinated well at 30°C–34°C, ‘Summer Queen’ and ‘Suico’ at higher temperatures of 32°C–36°C, and ‘King Ruby’ and ‘Sunny Shine’ at yet higher temperatures of 34°C–36°C. Germination was highest in ‘Minami-jujisei’ and was highest at 36°C, but decreased at lower and higher temperatures, indicating a limited favorable temperature range. In purple passion fruit (P. edulis), the favorable temperature range was lower than that of the hybrids and the thermal response varied between varieties. Kagoshima strain pollen germinated well at 28°C–32°C, and Amami wild strain at 28°C–34°C. Purple passion fruit germination tended to decrease slightly at lower temperatures. In yellow passion fruit (P. edulis f. flavicarpa), pollen of each cultivar and variety germinated well at 36°C, indicating a limited favorable range similar to that of ‘Minami-jujisei’. Sweet passion fruit (P. alata) pollen germinated well at 28°C–32°C, similar to the purple passion fruit. Water lemon (P. laurifolia) pollen germinated well at cooler temperatures of 26°C–28°C and remained generally high. Our results indicate that heat tolerance of pollen germination varies by approximately 2°C among hybrid passion fruit cultivars.

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  • Satoshi NAKAMURA, Simpore SAIDOU, Albert BARRO, Dambinga JONAS, Monraw ...
    2020 Volume 64 Issue 2 Pages 97-106
    Published: 2020
    Released: July 02, 2020
    JOURNALS FREE ACCESS

    Local phosphate rock use in sub-Saharan Africa (SSA) has immense potential to enhance African crop productivity. The effects of Kodjari phosphate rock direct application (PRDA) were studied in a rain-fed lowland rice (Oriza Sativa L.) fields with two levels of N applications, under different duration of submergence affected by seasonal flooding in the Sudan Savana of Burkina Faso. During the first year, PRDA with 90 kg N ha-1 did not affect rice yields whereas PRDA with 30 kg N ha-1 resulted in 91% yield obtained by using triple super phosphate (TSP). However, in the following season, successive PRDA indicated comparable effects as those of TSP application with both 30 and 90 kg N ha-1. Although TSP application indicated higher residual effects than that of PRDA, our investigation identified capital P replenishment by PRDA in the rain-fed lowland-rice cultivation area in the Sudan Savanna. Longer submergence duration resulted in higher PRDA effects. In conclusion, the high potential of PRDA on lowland rice was demonstrated in the Sudan Savanna zone. Considering previous studies, PRDA can be regarded as an effective technical option for lowland rice cultivation in the SSA. Although the effects of initial PRDA might have been depressed under water-limited conditions, it can contribute to improvement of soil P availability with replenishment of capital P for enhancing lowland rice production in SSA.

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