Native arbuscular mycorrhizal fungi and Nauclea orientalis for potential reclamation of tropical coal mining areas

Abstract

Reclaiming tropical coal mines is a formidable task. The symbiosis between AMF and plants like Nauclea orientalis is crucial for thriving in tough environments. This study aimed to assess the potential of native AMF and N. orientalis in overburden pit soil for post-mining reclamation. Fifteen AMFs isolated from post-coal mining were screened for nutrient uptake, plant growth, and colonization using Sorghum bicolor as hostplant. The top three AMFs were rDNA amplicon sequenced and further analyzed for their spore ontogeny at varying pH and aluminum concentrations. The most promising AMF strains were then tested by inoculating them into N. orientalis growing in four soil substrates: soil (S), overburden (O), soil mixed overburden (v/v 1:1, M1), and soil mixed overburden (v/v 1:3, M2). Non-inoculated plants served as control. Plant biomass, AMF colonization, root and shoot P, Al, Fe concentrations, and soil chemical properties were analyzed. Phylogenetic analysis revealed the three best-screened AMFs were Acaulospora mellea, Uncultured Glomus gene clone: N8-89, and Glomus clarum isolate AU402B. Overburden resulting from coal mining led to decreased soil pH and P levels while increasing concentrations of Al3+, H+, S, Fe, and Mn. A. mellea, Uncultured Glomus, and G. clarum demonstrated high P, K, Mg uptake and yield. G. clarum exhibited the best spore ontogeny at pH 4.5 and Al concentrations of 2 µM and 5 µM. Additionally, G. clarum, alongside N. orientalis, mitigated the toxicity of soil Al, Fe, and Mn. G. clarum improved plant growth in M1 and M2 and produced high plant biomass in OM and M2M. These findings suggest that the application of selected native AMF can significantly enhance plant adaptation in challenging conditions, potentially reducing the necessity for topsoil in reclamation efforts by 50–75 %.