Genotype-dependent growth and reproductive responses of Bambara groundnut to foliar-applied Moringa oleifera-mediated silver nanoparticle suspensions

Abstract

Bambara groundnut remains largely unexplored in studies of foliar-applied biogenic silver nanoparticle formulations, particularly with respect to genotype-specific responses. We evaluated three Bambara groundnut genotypes (MOK 01, MOK 02 and PTG 01) exposed to 0, 20, 40 and 60 mg L⁻¹ of Moringa oleifera-mediated silver nanoparticle (AgNP) suspension in a 3 × 4 factorial randomised complete block design with four replications. Vegetative, phenological and reproductive traits were analysed at the pot level using factorial models that included block, genotype, concentration and genotype × concentration interaction. Responses differed markedly among genotypes and traits. MOK 02 plant height increased from 18.75 ± 1.50 cm in the control to 28.50 ± 5.80 cm at 20 mg L⁻¹, whereas PTG 01 recorded its lowest height (17.75 ± 1.89 cm) and leaf number (27.50 ± 1.73) at 60 mg L⁻¹. Pod production increased at 40–60 mg L⁻¹ in MOK 02 and PTG 01, while MOK 01 pod width declined significantly from 9.60 ± 0.87 mm in the control to 7.07 ± 0.13 mm at 20 mg L⁻¹. Days to 50% flowering and seeds per pod were not significantly affected by concentration. Principal component analysis of nine directly measured traits explained 74.6% of total variation in the first two components and separated trait responses primarily along plant-size, leaflet, pod-dimension and pod-number gradients. Overall, the treatment produced non-linear, genotype-dependent responses rather than a uniform stimulatory effect. These findings support further mechanistic and multi-environment evaluation, but do not justify a general concentration recommendation or attribution of the response to the nanoparticle fraction alone.