Evaluation of single and mixed virus inoculated Bambara Groundnut landraces for nodulation and nitrogen fixation

Abstract

Bambara groundnut (Vigna subterranea [L.] Verdc) enriches soils by forming a symbiotic relationship with nitrogen-fixing and stem-nodulating bacteria. Virus infections, however, limit the plant's ability to fix nitrogen. The study evaluated the nodulation and nitrogen-fixing ability of Bambara groundnut landraces (Vg 01, Vg 02, Vg 03, Vg 04, and Vg 05) under single and mixed virus infections of Blackeye cowpea mosaic virus (BlCMV; Potyvirus), Cowpea mild mottle virus (CPMMV; Carlavirus), BlCMV+CPMMV, and CPMMV+BlCMV. The experiment was conducted under screenhouse conditions, using a completely randomised design with three replications. The results showed that the landraces varied significantly (p<0.05) in their nodulation and symbiotic effectiveness (SE). The highest number of nodules (7 per plant) was observed in Vg_04 followed by Vg_05 (6 per plant), and Vg_01 had the lowest of 5 nodules per plant. The highest reduction in the number of nodules per plant was 54.1 %, dry weight of shoot 48.6 % and root 43.8 %; length of shoot and root reduced by 43.1 % and 59.3 %, respectively in BlCMV+CPMMV treated plants. Nitrogen-fixing efficiency of the landraces varied from ineffective (IE), in BlCMV (SE = 29.1 %) and BlCMV+CPMMV (SE = 32.0 %) to poorly effective (PE) for CPMMV (SE = 35.6 %) and CPMMV+BlCMV (SE = 36.4 %) while the control treatment was effective with average percentage SE of 70.7 %. These results suggest the need to protect plants from virus infections to guarantee desirable yield and food security