Different response of Alyssum montanum and Helianthus annuus to cadmium bioaccumulation mediated by the endophyte fungus Serendipita indica

Environmental pollution by heavy metals is a severe issue worldwide. Microbe-assisted phytoremediation is a safe, inexpensive, and promising strategy in refinement of metal-polluted regions. Current in vitro work was installed to study effects of the endophytic fungus Serendipita indica on some physiological traits and cadmium (Cd) bioaccumulation of Alyssum montanum and Helianthus annuus seedlings grown in MS medium, under varying levels of Cd (0, 20, 40 and 60 mg Cd/l medium). Even though Cd stress induced phyto-toxicity in both tested species, but a significant improvement was found in biomass accumulation, photosynthetic pigments content, and chlorophyll fluorescence indicators in inoculated seedlings by S. indica under different doses of Cd in media. The non-infected A. montanum plantlets accumulated more Cd in shoot than root, and illustrated the properties of an accumulator species as evidenced by translocation factor (TF) and bioaccumulation factor of shoot (BFS) higher than 1. Contrary to this, un-colonized H. annuus seedlings had higher amount of Cd in root than shoot and showed a phyto-stabilizer feature, as evidenced by TF˂1 and bioaccumulation factor of root (BFR) higher than 1. Presence of S. indica significantly enhanced Cd accumulation in root, while it noticeably diminished Cd amounts of shoot in both A. montanum and H. annuus seedlings, so that inoculated plants had higher values for BFR against lower values for BFS and TF, in compare to non-inoculated ones. These findings indicated that S. indica can be considered as a bio-fertilizer to improve the physiological characteristics of tested species under Cd stress, as well as a bio-stabilizer of Cd in the roots of A. montanum and H. annuus in the regions exposed to toxic levels of Cd.