Selection and characterization of novel zinc-tolerant Trichoderma strains obtained by protoplast fusion

Abstract

Aim: To develop new Trichoderma strains, capable of removing toxic heavy metal ions from polluted environments, via protoplast fusion. Methodology: Trichoderma parental strains (T. viride and T. koningii) along with their ten fusants (Tk+Tv 1, Tk+Tv 2, Tk+Tv 3, Tk+Tv 4, Tk+Tv 5, Tk+Tv 6, Tk+Tv 7, Tk+Tv 8, Tk+Tv 9 and Tk+Tv 10) were obtained from the Department of Plant Pathology, Junagadh Agricultural University, Junagadh. The strains obtained by protoplast fusion were examined for their ability to remove toxic heavy metal ions, especially zinc ion. Fourier-transform infrared spectroscopy (FTIR) was conducted to detect the zinc uptake mechanism of Trichoderma parental and their fusant strains. Results: FTIR results demonstrated the Zn ion uptake capacity of fusant strains was found to be higher than that of the parental strains (12.8 to 10.7 mg g-1 on a dry weight basis at 1300 ppm). The highest Zn ion mobility observed was 62.1 mg. kg-1 and the highest Zn ion mobility observed per strain was 12.4% in Tk+Tv 3, followed by 11.86 % in Tk + Tv 7, 11.84% in Tk + Tv 9 and 11.28% in Tk + Tv 10. Parental and fusant strains Tk + Tv 3, Tk + Tv 8 and Tk + Tv 10 confirmed the involvement of different functional groups for different concentrations of zinc during adsorption by the fungus. Interpretation: FTIR results identified greater metal removal capacity in the fusant strains, particularly for soil Zn ion. Zinc tolerance was higher in the fusant strains than in the parental strains. Thus, protoplast fusion is an effective and feasible method for constructing new strains that can be used for bioremediation of contaminated environments.