Stress tolerance activity and diversification of endophytic fungi from the medicinal plant Abutilon indicum

Abstract

This study aimed to assess the diversity of endophytic fungi isolated from Abutilon indicum using morphological and molecular techniques. The isolates were exposed to various levels of salinity, temperatures, and heavy metals, including Ag²⁺ and Zn²⁺, at concentrations of 3.6 and 11.5 mM. Thirty root segments were isolated from each plant and cultured on potato dextrose agar plates. Four endophytic fungi were randomly isolated from infected root segments, belonging to the genera Aspergillus, Meyerozyma, and Penicillium. The phylogenetic analysis revealed significant diversity among the isolates of Aspergillus welwitschiae, Aspergillus indologenus, Meyerozyma carpophila, and Penicillium citrinum, with a 99% similarity in their sequences. Most isolates were able to thrive under salt stress conditions at NaCl concentrations of 200 mM (26%), 400 mM (24%), 600 mM (21%), 800 mM (13%), and 1000 mM (16%). Tolerant to temperature, endophytes could survive in the range of 25 °C to 35 °C but could not survive above 50 °C. Heavy metals tolerance of 89% of these isolates led to a significant decrease in biomass production when exposed to Ag²⁺. Endophytic fungal isolates showed decreased sensitivity to Zn²⁺, but between 33% and 60% showed strong growth in conditions with high levels of Zn²⁺. These findings revealed that endophytic fungi of A. welwitschiae enhanced growth when exposed to various stress conditions. Our findings indicate that the presence of fungal endophytes in different stress conditions leads to significant growth, and this could be useful for phytoremediation purposes.