Distribution and diversity studies of endophytic and rhizospheric fungi associated with the mangrove, Acanthus ilicifolius, using amplicon sequencing-based metagenomic approach

Fungal endophytes exhibit a broad diversity and are found universally associated with all plant species, playing a vital role in enhancing the host plant's resilience against both biotic and abiotic stressors. In this investigation conducted in Mumbai, India, the Illumina MiSeq sequencing platform was employed to study the endophytic fungal diversity of the common mangrove, Acanthus ilicifolius and its rhizosphere utilizing the amplification of the fungal ribosomal ITS2 region. The results revealed the creation of 307 Operational Taxonomic Units (OTUs) from a total of 663,600 sequencing reads, clustered at a 97 percent similarity level. Evaluation using Simpson and Shannon indices indicated that the highest community diversity was observed in stem tissue compared to root and leaf samples. The total OTUs were categorized into five phyla, 41 orders, 89 families, and 133 genera, with Ascomycota being the predominant phylum at 76.9% relative abundance, followed by Basidiomycota at 22.87%. The most abundant genera in the soil were Malassezia (35%) and Aspergillus (29.5%), while Vishniacozyma (61%) dominated in leaf samples. Unlike stem and root, no single genus dominated these tissues. The findings demonstrated significant distinctions between the fungal endophytic communities in plant tissues and the fungal microbiome in the soil. Notably, the endophyte fungi community in roots exhibited a closer resemblance to stem samples than to leaf samples. FunGuild analysis also revealed characteristic communities in different samples indicating specific functions of these genera. Overall, this study provides novel insights into the intricate composition of endophytic fungi within the tissues of A. ilicifolius and its rhizosphere.