Diversity and host structure affinity of endophytic fungi associated with deltaic mangroves in Iko River Estuary, Nigeria

This study evaluates the diversity and host structure affinity of endophytic fungi in deltaic mangroves (Rhizophora. mangle, Lacugularia racemosa and Avicennia africana) of Iko River Estuary located in the Niger Delta of Nigeria. The endophytes were isolated using culture-dependent methods and identified on the basis of their cultural and morphological characteristics. An overall Simpson Diversity Index (SDI) of 0.9527 with a quantitative species diversity index (Shannon diversity index; HI) of 3.543 were obtained. The black mangrove (A. africana) community had the highest HI of 3.521 and maximum fungal emergence (Colony Frequency; CF of 75), followed by white mangrove (L. racemosa; HI of 2.982), while the least HI of 2.688 was observed for red mangrove (R. mangle). Black mangrove recorded a maximum fungal emergence (CF of 75) and the highest diversity (SDI of 0.9643). Its respiratory root (pneumatophores) was the most colonised (CF of 51) with an SDI of 0.9589. The pneumatophores harboured 43.6% of the culturable fungal colonies (CF = 172) encountered in the ecosystem. A rich species assemblage (56 species) was observed in the deltaic mangroves; however, only culture-dependent isolates were obtained. This explains the low number recorded for the three mangroves investigated compared to the over 200 species of fungal endophytes already associated with mangroves. The mangrove mycobiome was dominated by Aspergilli (50.58%)followed by Penicillium (9.30%) and Aspergillus niger with percentage CF of 30.86 was the most frequently isolated endophyte although statistical analysis revealed high evenness (e^H/S) in the occurrence of endophytes on mangrove plants and plant parts. The black mangrove stem had the most even (e^H/S value of 1) fungal community. Other fungal species, Aspergillus terreus (CF = 18.52%) and Absidia sp (CF = 12.35%) were also prevalent. This investigation provides a checklist of culturable species of endophytic fungi associated with Nigerian mangroves, many of which have been reported to have tremendous biotechnological potential.