Isolation and Screening of Fungal Endophytes for Arsenic-Metal Tolerance Potential and Seedling Growth of Rice (Oryza sativa L.) Under Induced Arsenic Stress Condition.

Endophytes are one of the symbiotic associations which can be successfully utilized to mitigate negative effects of abiotic stress in agricultural crops. Habitat adapted symbiotic fungal endophytes are known to impart heavy metal stress tolerance in host plants. Besides, endophytic fungi secrete secondary metabolites and enhance the plant's ability to tolerate stressful conditions. Therefore, this study was aimed at evaluating fungal endophytes of arsenic stress adapted plants for their arsenic tolerance potential. Present study yielded 83 arsenic tolerant fungal endophytes from the plants grown in arsenic-contaminated areas of Karnataka. These isolates were screened for arsenic tolerance at different arsenic (Sodium arsenite) concentrations (100 ppm to 2000 ppm). Among the isolates, eight endophytes (S1P1R1, S3P1S1, S3P1S3, S4P2L2, S5P1S1, S6P1S3, S8P1L4 and S10P1L1) were found efficiently enduring metal stress up to 2000 ppm with tolerance index >0.5. These isolates were further re-evaluated for arsenic tolerance in biomass assay. Significantly higher biomass was achieved in all eight endophytes at 100 PPM arsenic concentration compared to non arsenic control. However, fungal biomass relatively reduced with subsequent increase in arsenic concentration from 250 ppm to 2000 ppm. Further, these endophytes were evaluated for their ability to alleviate arsenic stress and growth promotion of rice seedlings under in vitro arsenic stress condition. Rice seedlings inoculated with fungal endophytes showed significant increase in shoot length under arsenic stress compared to control. Among eight endophytes, the isolate S3P1S1 significantly enhanced shoot and root length of rice. Therefore, data obtained in the present study revealed that the fungal endophyte, isolated from arsenic adapted plant has ability to mitigate arsenic stress and improve the rice growth under arsenic condition. [ABSTRACT FROM AUTHOR]