Growth Response of Vernonia hymenolepis (Sweet Bitter Leaf) Seedlings Inoculated with Arbuscular Mycorrhizal Fungi (AMF) under Fusarium Root Rot Stress in Calabar, Nigeria

Abstract

Background: Vernonia hymenolepis is an underutilized African leafy vegetable with important nutritional and economic value, but its productivity is severely threatened by soil-borne pathogens such as Fusarium oxysporum, necessitating sustainable management approaches such as the use of arbuscular mycorrhizal fungi (AMF) to improve growth and disease resistance. Aims: To determine the influence of two AMF strains on dry biomass of root, stem and leafs of Vernonia hymenolepis under pathogen stress. Study Design: The experiment followed an 8 × 3 completely randomized design, consisting of eight treatments with three replicates, for a total of 24 pots. Place and Duration of Study: Calabar in the south- south of Nigeria. A study was conducted between February and May, 2025. Methodology: Vernonia hymenolepis seedlings were inoculated with two arbuscular mycorrhizal fungi (AMF) strains Glomus mosseae and Glomus gigaspora and subsequently challenged with 50ml of a Fusarium spore suspension under field conditions. Fusarium root rot severity (FRR) and dry biomass were assessed at harvest, 12 weeks after emergence. Results: The results clearly indicate that all the pathogen stressed seedlings alone (Fo) had higher root percentage disease severity (20.00%) than their combined counterpart with AMF seedlings (Gm+Fo and Gm+Gg+Fo) 1.66% as the lowest. Generally, Vernonia hymenolepis seedlings inoculated with G. mosseae in combination with G. gigaspora and Fusarium (Gm+Gg+Fo) produced the highest significant (P≤ 0.05) root, stem and total dry weight with means values of 10.01, 10.72 and 32.76g/plant-1 . Vernonia hymenolepis plants infected with Fusarium (Fo) alone recorded the lowest severe root, stem, total and root: shoot ratio damage by the pathogen. However, inoculated seedlings with Gg, Gm+Fo and Gm+Gg+Fo gave the highest leaves dry weight and Gm+Gg+Fo recorded the highest root to shoot ratio with value 32.76g/g-1. Conclusion: Plants inoculated with arbuscular mycorrhizal fungi (AMF) are better able to withstand environmental stresses, including pathogen pressure, and can contribute to the rehabilitation of soils affected by soil-borne diseases in Calabar, Nigeria. Enhanced dry biomass accumulation represents a key mechanism through which mycorrhizal plants express resistance to pathogens.