Influence of Alectra vogelii inoculation and phosphorus fertilizer application on phenology, yield components and grain yield of bambara groundnut genotypes

In sub-Saharan Africa, the parasitic <i>Alectra vogelii</i> is seriously threatening Bambara groundnuts, farmers to suffer yield losses of up to 100 %. The objective of this study was to determine the effects of phosphorus (P) application and <i>Alectra vogelii</i> inoculation on Bambara groundnut genotypes for growth and reproductive phrase. The experiment was conducted in 2020 at the Henderson Research Station in Mazowe, Zimbabwe in a 2 × 2 × 26 factorial design with 26 genotypes arranged in a completely randomized design (CRD) with four replications, two P rates (0 and 20 kg ha-¹) and two levels of inoculation (with and without <i>Alectra vogelii</i>). Half of the perforated black plastic bags were inoculated with <i>Alectra vogelii</i> seeds. The results showed a significant (p < 0.001) interaction between P application and <i>Alectra vogelii</i> inoculation, leading to decreased <i>Alectra vogelii</i> counts after 109 days, days to maturity, days to flowering, and chlorophyll content. There was a significant (p < 0.001) interaction between Bambara groundnut genotypes and <i>Alectra</i>-inoculation on number of pods, pod weight, number of seeds, and grain yield. <i>Alectra vogelii</i> parasitism significantly (p < 0.001) decreased number of pods, pod weight, number of seeds, and grain yield across all groundnut genotypes. G2, G23, G24, and G25 genotypes exhibited tolerance to <i>Alectra vogelii</i>, with grain yield per plant of 4.82, 6.12, 5.65, and 5.34 g, respectively, outperforming other genotypes. It was found that the combination of 20 kg P ha^-1 with <i>Alectra</i>-resistant genotypes improved Bambara groundnut productivity.