Tropical Agriculture and Development
Online ISSN : 1882-8469
Print ISSN : 1882-8450
ISSN-L : 1882-8450
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Original Article
  • Tomohiro KONDO, Kakeru KOGA, Daiki SATO
    2020 Volume 64 Issue 4 Pages 161-164
    Published: 2020
    Released: April 23, 2021
    JOURNALS FREE ACCESS

    Demand for low acid passion fruit has been increasing, and cultivation methods, such as fertilizer management to produce low acid fruit is required. And so, the effects of N concentration in fertilizer solution on fruit quality were determined in this study. Fertilizer solutions, containing 6, 13, 25, 50, and 100 mM N, were applied to two-year-old passion fruit plants in sand culture. Artificial pollination was conducted and the number of fruits per plant was regulated to be six. Length of the fruit-bearing vine and leaf, SPAD value, stomatal conductance, and leaf mineral contents were measured. Just after harvest, fruit weight, and dimensions were measured and the days after pollination to harvest (DAP) was recorded. After a 10-day-storage at 25 °C, titratable acidity (TA), total soluble solid (TSS), and juice content were measured. Vegetative growth and stomatal conductance increased as N concentration increased up to 50 mM. The number of flowers increased as N increased. Leaf N content increased as N concentration increased. Leaf Ca contents at 25 and 50 mM were higher than those in other treatments, while P, K, and Mg contents were not affected. TA decreased as N increased, while TSS was not affected. Fruit weight and dimensions were not affected, while juice content increased as N increased. DAP increased as N increased. Then, fruit quality was the highest at 100 mM, when leaf N content was 6.7 %. At 100 mM N treatment, DAP elongation might decrease acidity.

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  • Tomohiro KONDO, Hirokazu HIGUCHI
    2020 Volume 64 Issue 4 Pages 165-170
    Published: 2020
    Released: April 23, 2021
    JOURNALS FREE ACCESS

    Less acid passion fruit has been increasingly demanded for fresh consumption. In this study, effects of Ca concentration in fertilizer solution on passion fruit quality were examined. Twenty-four passion fruit plants, grown in pots filled with river sand, were used. From June 27 to September 27, 2013, 1000 mL of fertilizer solutions, containing 0, 2, 4, or 8 mM Ca, were applied to the plants twice a week. A neutral salt, CaCl2, was used so as not to affect pH of the sand media. Artificial pollination was conducted from June 28 to August 2 and the number of fruits per plant was regulated to be eight. Titratable acid content in juice (TA) decreased and total soluble solid content (TSS) increased as Ca concentration increased up to 4 mM. Juice content, fruit weight and dimensions were not affected by Ca fertilizer. At 8 mM, necrosis occurred on two of the six plants, and the leaves fell greatly. Fruit from the severely-damaged plants had higher TA and lower TSS than that from non-damaged plant. Leaf Ca content increased as Ca concentration in fertilizer solution increased. Leaf mineral contents except for Ca and Mn, were not affected. In conclusion, Ca application was effective to produce high quality passion fruit and fruit quality was the highest with 4 mM Ca concentration in fertilizer solution and 2.5 % of leaf Ca content, though necrosis occurred on some plants at 8 mM Ca treatment.

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  • Hiroshi MATSUDA, Hirokazu HIGUCHI, Masanori OKABE, Tatsushi OGATA
    2020 Volume 64 Issue 4 Pages 171-177
    Published: 2020
    Released: April 23, 2021
    JOURNALS FREE ACCESS

    Passion fruit flowers were pollinated at various temperatures range from 28–42°C, and the fruit set and the number of seeds were recorded to determine the critical high temperature which negatively affected to the fruit set. Other flowers which were detached just before anthesis were incubated and pollinated also at various temperatures. The germination of the obtained pollen was tested on agar medium, and pollen-tube growth in pistil was observed anatomically to determine the thermal response of pistil receptivity. Fruit set was more than 90% when daytime temperatures were regulated at 28–34°C. Fruit set decreased at temperatures ≥38°C. Flowers did not set fruit at 42°C. The number of seeds reduced at temperatures ≥36°C. Pollen tubes reaching the embryo sac were observed within 24 h after pollination in all detached flowers which were incubated at 28–32°C. Whereas at incubation temperatures ≥34°C, pistil morphological disorder was observed in all detached flowers, and pollen tubes did not reach the embryo sac within 24 h. Pollen germinated on the stigma without elongation into the style, even 24 h after pollination at 40°C. Germination percentages of the pollen, which was obtained from detached flowers incubated at 28–40°C, did not vary on agar medium. Although pistils on a detached flower were damaged by high temperatures ≥34°C, those growing under orchard condition did not show any symptom of damages at 36°C.

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  • Aki KUBOTA, Yosri ATTA, Ahmed ABDEL-FATTAH, Sayed El-BEHLAK, Yoshiya S ...
    2020 Volume 64 Issue 4 Pages 178-188
    Published: 2020
    Released: April 23, 2021
    JOURNALS FREE ACCESS

    A study to elucidate the possibility of water-saving irrigation methods for maize (Zea mays L.) by reducing frequency and wetting area was conducted in 2013 and 2014 on Vertisols of the Nile Delta. The water-saving methods tested were prolonging the interval by about 1 week and strip method with wide planting bed which results in reducing number of irrigation ditches by 50%. The water-saving ratio was higher with strip method (26 - 31%) than prolonging the interval (8 - 19%). The growth, photosynthetic rate, and grain yield of maize plants were investigated under 4 treatments, i.e. the combination of interval (about 2 weeks or 3 weeks) and method (furrow or strip). Although the treatments had different effects in 2 years, our results can suggest that prolonging the interval by about 1 week from the conventional interval has a risk of yield reduction in the field with soil clay contents equal to or less than 50%, while, strip method has possibility to sustain the grain yield of maize and to improve water use efficiency, calculated as the grain yield divided by the total amount of irrigation water, as much as 71% when irrigation interval was practiced as conventional. Under the prolonged irrigation interval, maize with strip method showed low photosynthetic rates caused by water deficit. Thus, the strip irrigation method with the conventional interval is recommended for saving limited water resources without yield reduction of maize in the Egyptian Nile Delta.

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  • Kanako SUZUKI, Kensuke OKADA, Takeru HIGASHIMAKI
    2020 Volume 64 Issue 4 Pages 189-200
    Published: 2020
    Released: April 23, 2021
    JOURNALS FREE ACCESS

    The micro-dosing (MD) technique has been disseminated in the Sahel region of West Africa to ensure that farmers make efficient use of affordable amounts of chemical fertilizer. However, it has been observed that unexpected drought conditions right after seeding often result in serious damage to seeds having received MD of chemical fertilizer. This is due to the acidity of the fertilizer. Hence, we needed to verify the efficacy of the MD technique in the Sahel region. Field tests were conducted in farmers’ fields of two villages in Niger as well as demonstrations to show the soil management method of combining the MD technique and organic matter (OM) input. There were four treatments: zero application as control, fertilizer application by MD sole, OM application sole, and co-application of fertilizer by MD and OM.

    Sole fertilizer application by MD did not show a positive effect on pearl millet growth and yield compared to control. However, the application of OM sole and co-application of fertilizer using MD and OM had a high potential to enhance the shoot dry matter and grain yield of pearl millet by improving the level of soil fertility and nutrient uptake. These results indicated the importance of OM input into the Sahelian sandy soil with low capacities of nutrient capture and buffer to enhance the positive effect of chemical fertilizer input.

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  • Yoshinori YAMAMOTO, Tetsushi YOSHIDA, Fransiscus Suramas REMBON, Muyan ...
    2020 Volume 64 Issue 4 Pages 201-211
    Published: 2020
    Released: April 23, 2021
    JOURNALS FREE ACCESS

    The growth and starch accumulation processes of sago palm with age in the natural forest were investigated in South Sorong, West Papua, Indonesia. The surveyed natural forest seemed to be a nearly pure sago palm forest and have reached the climax forest stage. The sucker density was lower than that of the cultivated garden, and the trunk density (trunks of 0.5 m or more) was almost equal. In addition, the trunk length at the flowering stage was longer than that in the cultivated garden, and the trunk frequency during the flowering to the dying/dead stage was higher. In the natural forest, it was difficult to estimate palm age, thus the number of leaf scars and leaves (No. LS + L) was used as an index of palm age. Until the No. LS + L was about 80 (about 10 m in trunk length), there was almost no increase in the percentages of dry matter and starch in the pith. However, afterward, these percentages and the starch content of the pith increased rapidly. The average starch content at the harvest stage was about 360 kg, but its variation was large among the individuals. The sago palms in the natural forest had lower percentages of dry matter and starch in the pith even at the optimal harvest stage, and the starch productivities per trunk length, fresh weight, and volume were lower than those of the cultivated sago palms.

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  • Masashi YAMAMOTO, Yohei SHIMAJIRI, Kenji NASHIMA, Toshiya YAMAMOTO
    2020 Volume 64 Issue 4 Pages 212-217
    Published: 2020
    Released: April 23, 2021
    JOURNALS FREE ACCESS

    Chromosome analysis of pitaya (Hylocereus spp.), a tropical fruit crop of the vine cactus, was conducted. All experiments were carried out using root tips derived from cutting plants as materials. Good chromosome samples all chromosomes relatively extended and well-spread without cytoplasm were prepared by the enzymatic maceration and air-drying method (EMA). The chromosome numbers of H. undatus, H. costaricensis, and H. megalanthus were 2n = 22, 22, and 44, respectively. In H. undatus and H. costaricensis, CMA-positive (+) bands were observed in telomeric positions of two chromosomes. DAPI-negative bands (–) corresponded to CMA+ bands. The CMA+/DAPI- bands were observed at the telomeric position of four chromosomes in H. megalanthus. When fluorescence in situ hybridization of rDNA was performed, the 18S-5.8S-25S rDNA sites were detected in telomeric positions of two chromosomes of H. undatus and H. costaricensis and four chromosomes of H. megalanthus. The 18S-5.8S-25S rDNA sites corresponded to the CMA+/DAPI- bands.

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