Evaluation of Abiotic Stress Tolerance and Compatibility of Native Isolates of Trichoderma spp. of Kasargod District, India

Aim: To evaluate the selected native isolates of Trichoderma spp. of Kasaragod district for abiotic stress tolerance and compatibility assessment with other biocontrol agents. Study Design: CRD. Place and Duration of Study: Department of Plant Pathology, College of Agriculture, Padannakkad, between November 2023 and November 2024. Methodology: The selected Trichoderma isolates Tr-5, Tr-12, Tr-41, Tr-43 (Trichoderma asperellum) and Tr-40 (Trichoderma lixii) were subjected to various abiotic stresses, namely low (4°C, 10°C and 15°C) and high (30°C, 45°C and 55°C) temperatures, salinity (0.5M, 1.5M and 2.5 M NaCl) and drought (10%, 30% and 40% PEG). The PDA was embedded with different NaCl and PEG concentrations to test the salinity and drought tolerance. After 4 days of inoculation (DAI), radial growth of Trichoderma isolates in treatments and controls was recorded. The compatibility of these Trichoderma isolates was checked with the other bio-control agents viz., Pseudomonas fluorescens, Metarhizium anisopliae, Lecanicillium lecanii and Beauveria bassiana using the dual culture technique. Results: In the temperature tolerance study, the selected isolates did not show any radial growth at 4°C, 10°C, 45°C, and 55°C.At 15°C, slight mycelial growth was observed, and the optimal range was found to be 30°C for good mycelial growth. The tolerance to salinity was up to 0.5M NaCl, but only in Tr-5 (0.83cm), Tr-12 (0.91), and Tr-40 (0.8) isolates; the mycelial growth was observed at 1.5M NaCl. At 10% PEG, the radial growth of isolates was on par with the control. Upon increasing concentration, radial growth of Trichoderma isolates was decreased/ absent along with sporulation. In the compatibility study, Trichoderma isolates were found to be compatible with P. fluorescens, M. anisopliae, L. lecanii and B. bassiana. But with fungal biocontrol agents, only Tr-40 showed incompatibility with M. anisopliae (66.67%), L. lecanii (33.58%), but was compatible with B. bassiana. Conclusion: In this study, all five native Trichoderma isolates, Tr-5, Tr-12, Tr-40, Tr-41 and 43 showed high tolerance to abiotic stresses at an optimum range of temperature (30oC), NaCl (0.5M), and PEG (10%). The isolates of Trichoderma spp. were compatible with bacterial and fungal bio-control agents except Tr-40.