Arbuscular Mycorrhizal Fungal Diversity in <i>Taxus contorta</i> Griff. Assessed Through Morphology and Amplicon Sequencing

Taxus contorta Griff., an important conifer of the Western Himalaya and a natural source of the anticancer drug Taxol, has experienced severe population decline due to overexploitation. Despite its ecological and medicinal significance, its mycorrhizal status has remained unclear, although it predominantly forms arbuscular mycorrhiza (AM), but reports of ectomycorrhizal associations also exist. In this study, mycorrhizal associations of T. contorta were examined through morpho-anatomical and molecular approaches, complemented by in-vitro mycorrhizal synthesis. Results revealed no evidence of ectomycorrhizal colonization; instead, Paris-type arbuscular mycorrhizal associations were observed, with colonization ranging from 45.54 ± 4.25% to 67.31 ± 5.71%. A total of 29 AMF species from 10 genera were identified in the rhizosphere soil, with Rhizoglomus intraradices and Glomus microcarpum as dominant taxa. The metabarcoding targeting the V4 region of the 18S rRNA gene identified 13 operational taxonomic units (OTUs) of AM fungi within T. contorta roots. Among these, three genera, Paraglomus, Glomus and Acaulospora, were identified, while more than half of the sequences could only be classified up to class level, indicating that arbuscular mycorrhizal diversity in the Himalaya remains largely unexplored. Mycorrhizal colonization peaked during active growth season, while AMF spore diversity was higher in dormant season. Both colonization and diversity were influenced by altitude, vegetation and soil properties. The dominance of specific AMF taxa suggests potential use as effective inoculants in the propagation of T. contorta in nursery, while insights into environmental influences may guide the selection of suitable sites for afforestation programs aimed at conserving this conifer.