ORIGINAL RESEARCH article
Front. Agron.
Sec. Plant-Soil Interactions
Plant growth, symbiotic N2-fixation, carbon accumulation and water-use efficiency of 63 common bean (Phaseolus vulgaris L.) genotypes grown under field conditions at Malkerns, Eswatini using the 15N natural abundance technique
Provisionally accepted
Rotondwa Pascalia Gunununu1*
Felix Dapare Dakora2- 1Crop Sciences, Tshwane University of Technology Faculty of Science, Pretoria, South Africa
- 2Chemistry, Tshwane University of Technology Faculty of Science, Pretoria, South Africa
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Abstract Common bean (Phaseolus vulgaris L.) is consumed worldwide and is the third most important food legume after soybean and groundnut. The aim of this study was to evaluate plant growth, N2-fixation, C accumulation and water use efficiency of 63 common bean genotypes grown in Malkerns, Eswatini under field conditions. The data revealed marked (p≤0.05) differences in shoot dry matter (SDM) yield, N concentration and content, δ15N, the proportion of N derived from symbiotic fixation (%Ndfa) and the N-fixed among the 63 common bean genotypes. Common bean plants %Ndfa values between 19.6-88.4 %, contributed 2.7-66.8 kg N-fixed ha-1 to the soil, while soil N-uptake ranged from 3.7-54.01 kg ha-1. Out of the 63 test genotypes, 40 genotypes obtained more N from the soil than from symbiosis, implying that the N2-fixing efficacy of the microsymbionts nodulating common bean in Malkerns were low. The results further revealed shoot δ13C values ranging from -30.11‰ to -26.33‰, indicating differences in plant water use efficiency amongst different common bean genotypes. There was a significant positive correlation between δ13C and N content (r=0.25**), and also between N-fixed and shoot dry matter (r = 0.88***), indicating a functional link between N2-fixation and photosynthesis. Taken together, the findings indicate that, increased N2-fixation is linked to improved photosynthetic activity, plant growth and water use efficiency in the bean plants. Keywords: Nitrogen fixation, %Ndfa, grain yield, Water-use efficiency
Keywords: %Ndfa, common bean, grain yield, Nitrogen Fixation, water-use efficiency
Received: 25 Sep 2025; Accepted: 10 Dec 2025.
Copyright: © 2025 Gunununu and Dakora. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Rotondwa Pascalia Gunununu
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