Impact of Rhizobium spp. on nodulation of cultivated (Vigna unguiculata) cowpea and soil fertility in southwestern Nigeria
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Date
2026-01-12
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Springer Nature
Abstract
Cowpea, an essential legume in the semi-arid regions of Sub-Saharan Africa, often experiences low yields due to poor cultivars, inadequate management practices, and limited agricultural inputs. This study evaluated the impact of Rhizobium inoculation of different species on cowpea nodulation and soil fertility in Oyo town, Nigeria. Three Rhizobium spp. were isolated from the root nodules of Arachis hypogaea (BMP_MO, BMP_MA, and BMP_MK). A cowpea breeding line (IT95K-207-22) was grown in sterilized soil; the plants were inoculated with three Rhizobium species, a combination of two species, and a non-inoculated control for 6 weeks in a pot experiment. The experiment followed a 1 × 5 factorial in a completely randomized design with two replications. Data on nodule number, weight, colour, and soil fertility were collected and analyzed. Inoculation with Rhizobium species resulted in nodule formation on the roots of all three species and the consortium. Plants inoculated with BMP_MN_24 produced the significantly highest nodule weight (g) (0.3375), followed by BMP_MO_24 (0.2733), and the control (0.1524). However, BMP_MK_24 had the lowest nodule weight (0.0284). BMP_MK_24 was identified as Rhizobium leguminosarum (PX671459), BMP_MN_24 as Rhizobium sophorae (PX583111.1), and BMP_MO_24 as Rhizobium leguminosarum (PX583112.1). Rhizobium leguminosarum (BMP_MK_24) improved soil conditions, while Rhizobium sophorae (BMP_MN_24) enhanced cowpea nodulation more effectively than the other inoculants studied. These strains can be utilized as potential bio-fertilizers.
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Keywords
Cowpea, Nodulation, Rhizobia inoculants, Rhizobium species, Sterilized soil