Assessment of Fungicide Compatibility with Native Trichoderma Isolates from the Rhizosphere of Kiwifruit (Actinidia deliciosa A. Chev.)

Abstract

Kiwi (Actinidia Deliciosa A. Chev.), an introduced fruit crop in Jammu & Kashmir, India, is affected by a number of diseases, particularly root diseases that reduce its yield potential significantly. The present investigation was conducted during the months of July-September 2025 using rhizospheric soil samples collected from kiwifruit orchards in Pulwama and Baramulla districts of Jammu and Kashmir, India. The study aimed to isolate native Trichoderma spp. from kiwifruit rhizosphere soils and evaluate their compatibility with commonly used fungicides under in vitro conditions. Sixteen Trichoderma isolates were obtained using the serial dilution technique on Potato Dextrose Agar (PDA) and purified through single spore/hyphal tip methods. Based on rapid radial and profuse mycelial growth, and early sporulation at 25 ± 1 °C, two fast growing isolates, TAR-2 (Trichoderma Arihal isolate 2) and TWA-3 (Trichoderma Warpora isolate 3), were selected for compatibility studies. Fungicide compatibility was assessed using the poisoned food technique. Results revealed significant variation in growth inhibition among fungicides. Carbendazim 50 % WP (0.1 %) and Carbendazim 12 % + Mancozeb 63 % WP (0.2 %) exhibited near-complete inhibition (>99 %) of both isolates, indicating strong incompatibility. In contrast, Mancozeb 75 % WP (0.3 %) and Metalaxyl 35 % WS (0.1 %) showed negligible inhibition (<1 %), demonstrating high compatibility. Copper oxychloride 50 % WP (0.3 %) and Fosetyl-Al 80 % WP (0.1 %) caused moderate, concentration-dependent reductions in mycelial growth but did not completely suppress colony development, suggesting partial compatibility. Statistical analysis confirmed significant differences among treatments at the 5 % level of significance. The findings highlighted that non-benzimidazole fungicides such as Mancozeb, Metalaxyl, Copper oxychloride, and Fosetyl-Al can be safely integrated with selected Trichoderma isolates in integrated disease management (IDM) programmes for kiwifruit. Conversely, Carbendazim-based formulations should be avoided when applying these biocontrol agents. The study reinforced the importance of selecting fungicides that are compatible with beneficial rhizospheric microorganisms for sustainable orchard management.