Community diversity and stress tolerance of culturable endophytic fungi from black seed (Nigella sativa L.)

Endophytic fungi constitute an important source of structurally diverse and pharmacologically active secondary metabolites. Most medicinal plants possess antimicrobial activity and host a number of endophytic fungi used in defense mechanisms against attack by pathogens. The aim of this study was to determine biodiversity of endophytic fungi isolated from black seeds , using morphological and molecular-based tools. Each isolate was, thereafter, subjected to stress tolerance through varying conditions of pH (2,3 and 12), salinity (3%,8% and 10%) and temperature (2 °C,25 °C,37 °C and 50 °C). Four hundred and ninety-two ( n =492) black seeds were used to isolate fungal strains on potato dextrose agar. A combination of microscopic examination and PCR amplification of Internal Transcribed Spacer (ITS 1 and ITS 4) regions were used to identify fungal isolates. One hundred ( n =100) endophytic fungi were successfully isolated with a 20% isolation rate. Under salt-stress conditions, most isolates managed to grow at 3% concentration, representing 88% fungal growth, with a maximum of 75–80.5 mm growth diameter. Fifty-eight percent (58%) of the fungi survived at pH 2, 16% survived at 37 °C, while there was no survival at a temperature higher than 50 °C. All the fungi belonged to the Ascomycota phylum, classified under Dothideomycetes (46%), Eurotiomycetes (39%) and Sordariomycetes (11%). The predominant genera identified were Penicillium (35%), Alternaria (26%) and Cladosporium (17%). The findings revealed that medicinal plants, including Nigella sativa , are a source of untapped novel endophytic fungi, with abundant therapeutic and agricultural applications.