Armillaria mellea sensu lato and related Armillaria species at the crossroads of taxonomy, ecology, and biotechnology: a multi-dimensional review.

Armillaria mellea (Vahl) P. Kumm. and related species in the A. mellea sensu lato complex are ecologically important basidiomycetes and key fungal partners in the cultivation of the fully mycoheterotrophic orchid Gastrodia elata. Because many historical reports labelled isolates simply as A. mellea before modern molecular delimitation, biological and applied conclusions require careful taxonomic interpretation. This critical review synthesizes literature on taxonomy, G. elata symbiosis, stress adaptation, selenium enrichment and applications. This review highlights four key findings. First, species delimitation cannot rely on morphology or ITS alone; authenticated vouchers, culture deposition and multigene or phylogenomic evidence are needed. Second, the Armillaria-G. elata association is a conditional interaction shaped by rhizomorph formation, enzymatic decomposition of woody substrates, host digestion of hyphae and cultivation environment. Third, stress tolerance and selenium enrichment are promising but remain under-standardized, with limited cross-strain comparisons, selenium speciation data and toxicity thresholds. Fourth, medicinal, food and enzyme-related claims are supported mainly by chemical, in vitro or cultivation data rather than mechanistic or clinical validation. Future work should integrate authenticated strain banks, isotope tracing, comparative genomics, standardized stress assays, selenium speciation and techno-economic evaluation. Accurate taxonomy is therefore essential not only for reproducible biological inference, but also for reliable strain selection, regulatory assessment and the safe commercial development of Armillaria-derived products.