Seed and soil provenance in the production and survival of Melanoxylum brauna seedlings

Melanoxylum brauna Schott is an endangered Atlantic Forest tree species whose seedling production is constrained by low survival under nursery conditions. This study evaluated seedling survival, morphophysiological performance, biochemical traits, and arbuscular mycorrhizal fungi (AMF) occurrence in seedlings produced from seeds collected at two locations and cultivated under different substrate combinations. Treatments included organic substrate, subsoil, soil collected near mother trees, and mixtures of sand, subsoil, mother-tree soil, and ground branches. Seedlings grown in 100% soil collected near mother trees showed the highest survival rate (97.5%), superior Dickson quality index, greater shoot and root growth, and enhanced photochemical efficiency (F_v/F_m), regardless of seed origin. These soils exhibited higher AMF spore density and the presence of Glomus macrocarpum, Sclerocystis spp., and Gigaspora spp., whereas organic substrates lacked mycorrhizal propagules and resulted in complete seedling mortality after 60 days. Biochemical analyses revealed increased accumulation of carbohydrates, proteins, lipids, and starch in seedlings grown in mother-tree soils, indicating improved metabolic performance. Overall, the results indicate that soil collected near mother trees functions as a natural bioinoculum source and is associated with improved seedling growth, physiology, and survival, possibly mediated by native microbial communities, including AMF.