Screening and determining the salt tolerance strain of Trichoderma under NaCl stress simulation

The aim of this study was to investigate the effects of salt stress on the growth of Trichoderma isolates collected from the rhizospheres of plants in different regions and identify salt-tolerant Trichoderma isolates. Salt-tolerant Trichoderma isolates were screened under different NaCl solutions by determining colony growth rates and the number of spores produced. Our results showed that isolates Trichoderma CT-3 and Trichoderma YT-3 had the highest levels of salt tolerance among the eight Trichoderma isolates collected from six rhizosphere soil samples from Zhangye and Minqin. Trichoderma CT-3 and Trichoderma YT-3 isolates exhibited high salt tolerance and presented no significant difference in colony growth compared with the control condition (0 mg·mL⁻¹ NaCl) after incubation for 6 days at an NaCl concentration of 60 mg·mL⁻¹ (P > 0.05). Spore production was higher in Trichoderma CT-3 (1.95 × 10⁷ cfu·mL⁻¹) and Trichoderma YT-3 (2.31 × 10⁷ cfu·mL⁻¹) than in the other six isolates under the same conditions, but lower than spore production under the control conditions. Therefore, Trichoderma CT-3 and Trichoderma YT-3 exhibit high salt tolerance at concentrations equal to or lower than 60 mg·mL⁻¹. Therefore, they have good prospects for application in microbial fertilizer.