Browsing by Author "Asiedu Robert"

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    Diversity of arbuscular mycorrhizal fungi in soils of yam (Dioscorea spp.) cropping systems in four agroecologies of Nigeria
    (Taylor & Francis, 2012) Dare Michael Olajire; Abaidoo R. C; Fagbola Olajire; Asiedu Robert
    The diversity of arbuscular mycorrhizal (AM) fungi in soils under a yam cropping system in four agroecologies of Nigeria was investigated. Soil samples were collected from yam fields at Onne (humid forest, high rainfall area), Ibadan (derived savanna), Abuja (Guinea savanna) and Ubiaja (humid forest, medium rainfall area). Soil characteristics, AM fungi species, spore abundance, Shannon diversity index, species richness and evenness were determined. A total of 31 AM fungi species was isolated from the four agroecologies with a range of 14–20 species found in a single location. Glomus species were the most abundant among AM fungi species with G. geosporum, G. intraradices and G. mosseae occurring in large populations in all locations. Ubiaja, which had a cassava/natural vegetation sequence before yam, had significantly higher spore abundance and species richness than the other locations, which had a yam/legumes or a maize/legume sequence before yam. However, diversity was significantly higher at Abuja, which had a maize/legume sequence with yam, than Ibadan, which had only a yam/ legume sequence. The study revealed significant diversity in AM fungal species across agroecologies in yam-growing regions. Further research on the functional consequences of changing composition of AM fungi species across the region is recommended.
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    Evaluation of White yam (Dioscorea rotundata) genotypes for arbuscular mycorrhizal colonization, leaf nutrient concentrations and tuber yield under NPK fertilizer application
    (Taylor & Francis, 2014) Dare Michael Olajire; Fagbola Olajire; Abaidoo R. C; Asiedu Robert
    Yield decline in yam may not only be due to soil nutrient depletion but also to the activity of soil microflora. Arbuscular mycorrhizal (AM) symbiosis helps in plant nutrition but may be affected by the application of fertilizer. The effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on the AM colonization, leaf nutrient concentrations, and tuber yields of eleven genotypes of Dioscorea rotundata were investigated at Ibadan, Nigeria. The soil was ferric luvisol. Eleven genotypes were selected from the previously conducted screening of 75 genotypes of D. rotundata for fertilizer response. Four application rates: 0, 200, 400, and 600 kg ha−1 of NPK 15-15-15 were applied in a split plot design with four replications. Fertilizer rate was the main plot and variety was the sub plot. Percentage AM colonization was significantly reduced at 600 kg ha−1 but not at lower rates when compared to zero rate and it was negatively correlated with leaf N, P, and zinc (Zn) concentrations. Leaf N concentrations were significantly increased at 200 kg ha−1 in five genotypes and at 600 kg ha−1 in two genotypes compared to zero application. Leaf P and K concentrations were decreased with the application of fertilizer in most of the genotypes. The NPK fertilizer of 15- 15-15 at the rate of 200–400 kg ha−1 gave yield response in eight genotypes of D. rotundata, with minimal or no effect on their AM colonization when compared to zero application. Long term study on the effect of fertilizer application on AM symbiosis in yam is recommended.