Browsing by Author "Nakei, Monica"

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Assessment of the soil suitability for soybean growth and the prospect biofertilizers use in selected areas of Tanzania
(Maximum Academic Press, 2023-10-19) Nakei, Monica; Venkataramana, Pavithravani; Ndakidemi, Patrick
The rapidly increasing global human population threatens the availability of safe and nutritious food. Among others, soil fertility degradation, insufficient use of proper fertilizers and scanty soil characterizations have major contributions in lowering the productivity of crops. To ensure the use of sufficient proper fertilizers for optimum crop productivity, it is important to evaluate the fertility status of soil which is a vital tool in deciding the type and the amount of fertilizer to be supplemented. This study aimed at evaluating soil fertility in the soybean growing and the non growing areas of Tanzania and to assess their suitability for growing the soybean crop as well as prospective use of rhizobia biofertilizers through the assessment of nodule formation in non-inoculated soybean plants grown in different farmers' fields. A total of 81 soil samples including those in soybean growing and non growing areas of Tanzania, were evaluated in terms of their fertility status through different physico-chemical parameters. From each field, three healthy plants with intense green leaves were selected for nodule counting. The study indicated that, most of the soils (85%) have medium acidic to neutral soil pH with 58% having sufficient organic carbon and 78% at risk of nitrogen deficiency. Soil pH, total N and OC had significant (p < 0.05) correlations (r) of 0.14, −0.22 and −0.27 with nodule number. The higher number of nodules were in medium acidic to neutral soils, with the highest number, 8.82 in neutral pH soils, indicating the favorability of the particular pH ranges for rhizobia activities. The results of this study suggest that most of the soils are suitable for the production of soybean and the use of rhizobia inoculants.
Evaluating Rhizobium and Bradyrhizobium species as potential biocontrol agents for root rot fungi in soybean seedlings
(Technology in Agronomy, 2024) Nakei, Monica; Venkataramana, Pavithravani; Ndakidemi, Patrick
Soybean (Glycine max) is among the legumes which are highly prone to soil-borne pathogens which causes root-rot diseases limiting the growth and development resulting to low yield of plants. This study was conducted to test the ability of three rhizobia strains, Rhizobium sp. TZSR12C, Rhizobium sp. TZSR25B and Bradyrhizobium sp. TZSR41A, in comparison with the commercial biocontrol (Trichoderma harzianum in suppressing the growth of root rot fungal pathogens (Fusarium solani, Rhizoctonia solani, Fusarium oxyporum, and Macrophominaphaseolina) under in vitro and greenhouse conditions. The rhizobium cell filtrates were used in testing their activities against fungal pathogens under in vitro while the solid biofertilizer formulations containing the respective rhizobia inoculants were used to inoculate the soybean seeds sown in pathogen contaminated soil under greenhouse conditions. Results showed that all rhizobia isolates and T. harzianum were capable of suppressing the fungal pathogens both under in vitro and greenhouse conditions with the highest inhibition zone (8.3 mm) and colony diameter (25.0 mm) being in Rhizobium sp. TZSR25B against F. oxyporum under in vitro conditions. Under greenhouse experiment, Rhizobium sp. TZSR12C had the highest performance in inhibiting the infection of plant up to 27.78% with severity of 5.56% in roots and 0.00% infection in foliage against the combination of F. solani, R. solani, F. oxyporum, and M. phaseolina. We found that, on their performance, the tested rhizobia strains can potentially be utilized as biocontrol agents against the fungal pathogens in the rhizosphere of soybean plants
Preliminary symbiotic performance of indigenous soybean (Glycine max)-nodulating rhizobia from agricultural soils of Tanzania
(Frontiers, 2023-01-26) Nakei, Monica; Venkataramana, Pavithravani; Ndakidemi, Patrick
Globally, the increase in human population continues to threaten the sustainability of agricultural systems. Despite the fast-growing population in Sub-Saharan Africa (SSA) and the efforts in improving the productivity of crops, the increase in the yield of crops per unit area is still not promising. The productivity of crops is primarily constrained by inadequate levels of soil nutrients to support optimum crop growth and development. However, smallholder farmers occasionally use fertilizers, and the amount applied is usually small and does not meet plant requirements. This is due to the unaffordability of the cost of fertilizers, which is enough to suffice the crop requirement. Therefore, there is a need for alternative affordable and effective fertilization methods for sustainable intensification and improvement of the smallholder farming system’s productivity. This study was designed to evaluate the symbiotic performance of indigenous soybean nodulating rhizobia in selected agricultural soils of Tanzania. In total, 217 rhizobia isolates were obtained from three agroecological zones, i.e., eastern, northern, and southern highlands. The isolates collected were screened for N2 fixing abilities under in vitro (nitrogen-free medium) and screen house conditions. The results showed varying capabilities of isolates in nitrogen-fixing both under in vitro and screen house conditions. Under in vitro experiment, 22% of soybean rhizobia isolates were identified to have a nitrogen-fixing capability on an N-free medium, with the highest N2-fixing diameter of 1.87 cm. In the screen house pot experiment, results showed that soybean rhizobia isolate significantly (P < 0.001) influenced different plant growth and yield components, where the average shoot dry weight ranged from 2.49 to 10.98 g, shoot length from 41 to 125.27 cm whilst the number of leaves per plant ranged from 20 to 66. Furthermore, rhizobia isolates significantly (P = 0.038) increased root dry weight from 0.574 to 2.17 g. In the case of symbiotic parameters per plant, the number of nodules was in the range of 0.33–22, nodules dry weight (0.001–0.137 g), shoot nitrogen (2.37–4.97%), total nitrogen (53.59–6.72 g), and fixed nitrogen (46.878–0.15 g) per plant. In addition, the results indicated that 51.39% of the tested bacterial isolates in this study were ranked as highly effective in symbiosis, suggesting that they are promising as potential alternative biofertilizers for soybean production in agricultural soils of Tanzania to increase productivity per unit area while reducing production cost.
Preliminary symbiotic performance of indigenous soybean (Glycine max)-nodulating rhizobia from agricultural soils of Tanzania
(Frontiers in Sustainable Food Systems, 2023-01-23) Nakei, Monica; Venkataramana, Pavithravani; Ndakidemi, Patrick
Globally, the increase in human population continues to threaten the sustainability of agricultural systems. Despite the fast-growing population in Sub-Saharan Africa (SSA) and the e
Soybean-Nodulating Rhizobia: Ecology, Characterization, Diversity, and Growth Promoting Functions
(Frontiers in Sustainable Food Systems, 2022-04-14) Nakei, Monica; Venkataramana, Pavithravani; Ndakidemi, Patrick
The worldwide increase in population continues to threaten the sustainability of agricultural systems since agricultural output must be optimized to meet the global rise in food demand. Sub-Saharan Africa (SSA) is among the regions with a fast-growing population but decreasing crop productivity. Pests and diseases, as well as inadequate nitrogen (N) levels in soils, are some of the biggest restrictions to agricultural production in SSA. N is one of the most important plant-limiting elements in agricultural soils, and its deficit is usually remedied by using nitrogenous fertilizers. However, indiscriminate use of these artificial N fertilizers has been linked to environmental pollution calling for alternative N fertilization mechanisms. Soybean (Glycine max) is one of the most important legumes in the world. Several species of rhizobia from the four genera, Bardyrhizobium, Rhizobium, Mesorhizobium, and Ensifer (formerly Sinorhizobium), are observed to effectively fix N with soybean as well as perform various plant-growth promoting (PGP) functions. The efficiency of the symbiosis differs with the type of rhizobia species, soybean cultivar, and biotic factors. Therefore, a complete understanding of the ecology of indigenous soybean-nodulating rhizobia concerning their genetic diversity and the environmental factors associated with their localization and dominance in the soil is important. This review aimed to understand the potential of indigenous soybean-nodulating rhizobia through a synthesis of the literature regarding their characterization using different approaches, genetic diversity, symbiotic effectiveness, as well as their functions in biological N fixation (BNF) and biocontrol of soybean soil-borne pathogens.