Abstract

The antagonistic activity of five selected isolates of Trichoderma spp. (Trichoderma harzianum CCM340, Trichoderma koningii CCM341, Trichoderma longibranchiatumNRRL11236, Trichoderma viride DSM63065 and Trichoderma viride) against Fusarium oxysporum f.sp. vasinfectum and Rhizoctonia solani, the causal agents of root rot of cotton plants grown in saline and non-saline soil, was studied in vitro and in vivo. Results indicated that F. oxysporum and R. solani were mostly inhibited by T. viride and least inhibited by T. longibranchiatum NRRL11236. Greenhouse test showed that for both pathogens, T. koningii CCM341 gave the highest disease control percentage (100%) in saline and non-saline soil and that T. harzianum CCM340, T. longibrachiatum NRRL11236 and T. viride DSM63065 gave the same disease control percentage (100%) in non-saline soil. In addition, the effect of Trichoderma isolates on several growth parameters of cotton plants was also studied. On the other hand, study on  metabolites such as amino acids (AA), fatty acids (FA) and plant growth hormones (PGH) produced by these Trichoderma isolates showed that T. viride was the highest in AA production and the only isolate that produced lauric acid (FA). The highest amount of gibberellic acid, indol-3-acetic acid and abscisic acid was produced by T. viride DSM63065, T. harzianum CCM340 and T. koningii CCM341, respectively. Also, the pH and temperature effects on Trichoderma mycelial growth were also evaluated. However, the application of Trichoderma spp. to soil infested with F. oxysporum and R. solani provided a good way for protection of cotton plants. Also,Trichoderma metabolites such as amino acids, fatty acids and plant growth hormones may be developed into several commercial biological control products to prevent development of several pathogenic fungi and / or to induce plant growth response. Evaluation of pH and temperature effects on Trichoderma isolates mycelial growth  showed that Trichoderma  strains were found to be able to display activities under a wider range of pH values and that they are mesophili.

Key words: Fusarium oxysporum, Rhizoctonia solani, cotton growth parameters, biocontrol agent, salinity.