Eco-physiological and physiological characterization of cowpea nodulating native rhizobia isolated from major production areas of Ethiopia

Sustainable Environment

Amsalu

Argaw

et al. 2021

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Enumeration of the native rhizobia population is important to determine the abundance of rhizobia in the soil and the achievement of inoculation. In Ethiopia, limited information is available on the population abundance of cowpea nodulating rhizobia. This study aimed to evaluate the population abundance of rhizobia nodulating cowpea and their relation with cropping history and soil properties in cowpea producing areas of Ethiopia. The abundance of rhizobia existing in the soils was assessed by the most probable number technique. The study revealed that the population abundance of rhizobia nodulating cowpea is high, ranging from 3.1 × 10 4 to 1.0 × 10 7 rhizobia cells g −1 of soil, and the population varied at each location. Besides, there was no statistically significant correlation between soil physicochemical properties and the rhizobial population. All the investigated soils had been cropped with cowpea in monoculture (sole cowpea), intercropping (mostly with sorghum and maize) and crop rotation for many years. Thus, the higher rhizobia population observed in this study is associated with the season factor and cropping history of the areas. In general, the soils of cowpea production areas in Ethiopia harbor adequate levels of rhizobia capable of nodulating cowpea, which are passable to provide satisfactory nitrogen fixation and nodulation.

Section: Introductionmentioning

confidence: 99%

Abundance of native rhizobia nodulating cowpea in major production areas of Ethiopia as influenced by cropping history and soil properties

Sustainable Environment

Amsalu

Argaw

et al. 2021

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“…Cowpea can fix atmospheric nitrogen through biological nitrogen fixation, a symbiotic association between legume host and soil‐dwelling bacteria commonly known as rhizobia, which makes it an important component of cropping systems (Kebede & Bekeko, 2020). With efficient nutrient management, especially nitrogen and phosphorus, cowpea can fix about 240 kg ha −1 of atmospheric nitrogen and make about 60–70 kg ha −1 nitrogen available for succeeding crops grown in rotation with it (Kebede et al., 2021). According to Bationo et al.…”

Section: Introductionmentioning

confidence: 99%

Nodulation potential and phenotypic diversity of rhizobia nodulating cowpea isolated from major growing areas of Ethiopia

Agrosystems Geosci & Env

Amsalu

Argaw

et al. 2022

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Rhizobia are legume specific, and they need to be characterized by different methods. This study assessed the nodulation potential and phenotypic diversity of rhizobia nodulating cowpea [Vigna unguiculata (L.) Walp.] isolated from major growing areas of Ethiopia. From 30 soil samples, 28 (93.3%) samples induced nodulation. Twenty-eight isolates obtained from nodulated plants were evaluated using presumptive tests and different phenotypic characteristics. On yeast extract mannitol agar (YEMA) containing Congo red (CR), the isolates produced colony colors that were whitish to pale pink. All isolates showed no growth on peptone glucose agar and the isolates were capable of growing on ketolactose medium but did not turn the media color to yellow. All the isolates were also confirmed to be gram-negative, rodshaped, and nonspore-forming. The colony texture study revealed that 78.57% of the isolates had a large mucoid colony, whereas 21.43% exhibited a large watery colony texture with diameters ranging between 1 and 5 mm. Depending on the colony color on YEMA containing bromothymol blue, 22 (78.57%) isolates were slow growing, whereas six (21.43%) isolates were fast-growing rhizobia. The cluster analysis based on phenotypic characteristics revealed a grouping of the isolates into two clusters at a similarity level of 75% and six further subclusters at a similarity level of ∼91%, indicating variations and diversity among the isolates. Overall, this study revealed significant variations among the cowpea nodulating rhizobial isolates and suggested that the soils of Ethiopia harbor populations of phenotypically diverse isolates. A further test to confirm these findings using genetic characterization and inclusion of reference strain is highly recommended. INTRODUCTIONCowpea [Vigna unguiculata (L.) Walp.] is a multifunctional legume crop that provides food for humans, feed for livestock, and serves as a valuable and dependable revenue-generating commodity for farmers and grain traders. Cowpea can fix Abbreviations: BTB, bromothymol blue; CR, Congo red; YEMA, yeast extract mannitol agar.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

“…Legumes also play a pivotal role in nutrient enrichment and cycling in agricultural production systems. Predominantly, the exceptional capacity of legumes to fix atmospheric nitrogen through symbiotic association with rhizobia, a root nodule bacteria that comprise Rhizobium, Bradyrhizobium, Sinorhizobium, Azorhizobium, and Mesorhizobium, could be used to increase agricultural productivity (Kebede, 2020a;Kebede et al, 2021). However, the success of this symbiotic association is dependent on the capability of legumes to form effective nitrogen-fixing symbioses with rhizobia.…”

Section: Introductionmentioning

confidence: 99%

Competency of Rhizobial Inoculation in Sustainable Agricultural Production and Biocontrol of Plant Diseases

Front. Sustain. Food Syst.

2021

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The rate of growth of the global population poses a risk to food security, demanding an increase in food production. Much of the world's cultivable soils also do not have ideal farming conditions such as soil health and fertility problem and increased pest attacks, which are challenges of food production. In this perspective, there is a need to increase agricultural production using a more economically and environmentally sustainable approach. As practices of agricultural production and improvement, rhizobial inoculants represent a practically effective, ecologically safe, and economically alternative means of realizing maximum agricultural production. This review addressed how rhizobial inoculation advances agricultural production through improving plant growth, nutrient availability and uptake, and yields by enhancing bio-fixation of atmospheric nitrogen and solubilization of soil nutrients. Besides, rhizobial inoculants offer biocontrol of plant diseases by providing resistance against disease-causing pathogens or suppression of diseases. Mechanisms involved in biocontrol of plant diseases include competition for infection sites and nutrients, activation of induced systemic resistance, and production of substances such as growth hormones, antibiotics, enzymes, siderophores, hydrogen cyanide, and exo-polysaccharides. Consequently, this approach is promising as sustainable agricultural practices have yet to supplement or replace chemical fertilizers, serving as a basis for future research on sustainable agricultural production. Despite the multifunctional benefits of rhizobial inoculation, there is a variation in the implementation of this practice by farmers. Therefore, researchers should work on eradicating farmers' constraints in using rhizobia, and future studies should be concentrated toward the methods of improving inoculant quality and promotion of the technology.