Enhancing growth and graft success of shea (Vitellaria paradoxa C.F. Gaertn) through targeted inoculation with indigenous arbuscular mycorrhizal fungi

Vitellaria paradoxa is a keystone species of West African agroforestry systems, yet its regeneration is constrained by slow juvenile growth and low grafting success. Arbuscular mycorrhizal fungi (AMF) have the potential to enhance seedling vigor, but their contribution to the production of graftable rootstocks remains poorly documented. This study evaluated the effects of six indigenous AMF inocula on mycorrhizal colonization, early growth, and graft success of V. paradoxa under nursery conditions. Seedlings were inoculated with six indigenous AMF inocula or left uninoculated as controls. Mycorrhizal colonization was assessed at 9 and 16 months after inoculation, while growth parameters were measured up to 9 months. The plants were then grafted using the terminal cleft grafting technique, and graft success was evaluated 90 days after grafting. The relationship between grafting success rate and plant growth was analysed using binary logistic regression, including collar diameter as a covariate. Mycorrhizal colonization differed markedly among inocula, with M3 and M2 showing the highest colonization frequency and intensity at 16 months. Inoculation significantly enhanced seedling growth, particularly collar diameter, with M1 and M3 producing the most vigorous rootstocks. Graft success was strongly improved by AMF inoculation, reaching 96% with M3 compared to 32% in uninoculated controls. Logistic modeling revealed a positive association between collar diameter and graft success. These results demonstrate that targeted inoculation with indigenous AMF inocula can substantially improve the production of graftable shea rootstocks and enhance graft success. Integrating AMF inoculation for vigorous seedlings offers a promising strategy to accelerate shea parkland restoration.