Diversity of endophytic mycobiota of tropical tree Tectona grandis Linn.f.: Spatiotemporal and tissue type effects

Abstract

Fungal endophytes were isolated from leaf, bark and stem of Tectona grandis Linn.f. sampled at four geographical locations in winter, summer and monsoon seasons. The recovered 5089 isolates were assigned to 45 distinct morphotypes based on morphology. The sequences of the internal transcribed spacers (ITS) of the nrDNA of some morphotypes were identical, but morphological differences were strong enough to consider these morphotypes as separate species. Forty-three morphotypes were assigned to ascomycotina and two to basidiomycotina. Ascomycotina was the predominating group with 99.7% of total isolates followed by basidiomycotina with only 0.3% of total isolates. Diaporthe (Phomopsis) species dominated the communities independently on tissue type, location or season. More than 60% of the examined tissue pieces were colonized by members of this species complex. While these endophytes are ubiquitous others were tissue or location specific. Tissue type had the strongest effect on the species evenness of the endophytic assemblage followed by geographical location and season. However, Shannon-Wiener index (H') significantly (p ≤ 0.001) varied with all three factors i.e. season, location and tissue type. Leaves supported the highest diversity across all the seasons and locations. In conclusion, all the three factors together determined the structure of endophytic mycobiota assemblage of T. grandis.

Figure 1

Phylogenetic tree constructed by neighbour-joining method using nrDNA ITS sequences generated during this study (as TGE) and sequences retrieved from GenBank using p-distance for nucleotides and the pairwise gap deletion choice.

Figure 2

Boxplot representation of variability of species diversity (H) with respect to location, season and tissue type. The first letter of the three-letter acronyms denotes the season (W, winter; S, summer; M, monsoon), the second the location and the third the tissue type (B, barks; L, leaf; S, stem).

Figure 3

Biplot (Principal components analysis) depicting the relationship between fungal endophyte taxa (arrows) and sampling units (tissue type, season and location). The longer the arrow the more influence has the fungus connected with it, and the further removed a sampling unit gets positioned from the centre the stronger its influence. The closer a sampling unit and a fungal taxon the stronger is their relationship. The first letter of the three-letter acronyms denotes the tissue type (B, barks; L, leaf; S, stem), the second the season (W, winter; S, summer; M, monsoon), and the third the location.