Characterization of Trichoderma asperellum RM-28 for its sodic/saline-alkali tolerance and plant growth promoting activities to alleviate toxicity of red mud

Abstract

Red mud (RM) is a highly alkaline, saline and sodic solid by-product released by alumina industries, which pose an economical and environmental problem and establishment of vegetation on these sites is a big challenge. In the present study, a fungus RM-28 exhibiting high tolerance to alkaline (pH 12), saline/sodic (NaCl 4%) was isolated from RM flooded rhizosphere soil of bermudagrass and tested its ability to reduce RM toxicity and promote the growth of sorghum-sudangrass seedlings. This fungus also exhibited high tolerance to heavy metal(loid)s (HMs) and desirable plant growth-promoting traits. This fungus was identified as Trichoderma asperellum based on its internal transcribed spacer (ITS) of rDNA and translation elongation factor-1α (TEF 1α) gene analysis. This fungus was effective in reducing the pH and solubilizing tricalcium phosphate under high alkaline and saline conditions in vitro. Further, RM-28 inoculation significantly lowered the pH and EC of the red mud from 11.8 to 8.2 and 2.23 to 1.42, respectively. Inoculation of RM-28 significantly improved the growth, chlorophyll content and reduced the oxidative stress of sorghum-sudangrass seedlings grown in red mud leachate. These observations suggest that T. asperellum RM-28 serves as potential source for the establishment of vegetation on red mud/red mud contaminated soils.

Keywords: Heavy metal(loid)s; Oxidative stress; P-solubilization; Red mud; Sodic-alkalinity; Trichoderma asperellum.