Endophytic fungal diversity in Terminalia arjuna (Roxb.) Wight & Arn. of Tripura, Northeast India at different sampling sites and plant organs

Endophytic fungi are ubiquitous in plant kingdom and play a vital role in balancing the microenvironments within the host plants. Fungal endophytes isolated from ethno-botanically important plants were the source of several secondary metabolites with potential biological activities. The present study has documented the variability of culturable endophytic fungi from Terminalia arjuna (Roxb.) Wight & Arn. (Combretaceae), a widely used medicinal plant of Tripura, North-east, India. A total of 613 fungal strains were isolated from 720 tissue segments viz. leaves, bark and root of T. arjuna. The highest numbers of endophytic fungal isolates were found to be colonizing in leaves (257) followed by barks (182) and the least number of isolates were obtained from roots (174). The fungal isolates were classified into 27 individual fungal strains based on morphological and microscopic features. A total of 9 endophytic fungal strains were identified using the nuclear ribosomal DNA internal transcribe sequence and were subjected to phylogeny analysis. Most of the identified morphotypes belonged to phylum Ascomycota. Among all the isolates, Diaporthe sp., Fusarium sp., Colletotrichum sp., Penicillium sp. were the most abundant fungal isolates from T. arjuna. The fungal orders namely Sordariomycetes was the most prevalent followed by Eurotiomycetes and Dothideomycetes. Colonization rate, isolation rate, colonization frequency and relative frequency results suggest that leaf segments harbors maximum endophytic fungi assemblage compared to bark and root tissues. The analysis of Shannon (H'), Simpson (1-D), Fisher alpha (a) and Brillouin (HB) indices had significant difference with locations and tissue type. The host plant harbor unique endophytic community composition in studied sampling locations and their colonization varied between the inoculated vegetative parts of the plant. As no such study has been undertaken in the North- eastern part of India, this pioneer study may enable to unearth novel fungal endophytes that might have beneficial role in plant growth promotion, stress tolerance etc.