PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Aims: To evaluate the in vitro antagonistic potential of seven systemic fungicides at concentrations of 500 and 1000 ppm and seven biological control agents against Alternaria alternata, the causal agent of Alternaria leaf blight of groundnut.

Study Design: Completely Randomised Design (CRD).

Place and Duration of Study: Department of Plant Pathology, College of Agriculture, Latur, Maharashtra, India. The study was carried out during 2025-2026.

Methodology: Alternaria alternata was isolated from infected groundnut plants showing small, irregular, scattered pale-yellow to light-brown spots on the leaves. Seven systemic fungicides (Carbendazim 50% WP, Tebuconazole 25.9% EC, Thiophanate methyl 70% WP, Propiconazole 25% EC, Hexaconazole 5% EC, Pyraclostrobin 20% WG and Difenoconazole 25% EC) were evaluated at concentrations of 500 ppm and 1000 ppm using the poisoned food technique. Seven bioagents (Trichoderma asperellum, T. harzianum, Aspergillus niger, T. hamatum, T. koningii, Pseudomonas fluorescens and Bacillus subtilis) were evaluated using the dual-culture technique on Potato Dextrose Agar (PDA).

Results: All tested systemic fungicides significantly inhibited pathogen mycelial growth compared with the control (P = 0.01). Tebuconazole 25.9% EC, Propiconazole 25% EC, Hexaconazole 5% EC and Difenoconazole 25% EC recorded complete inhibition (100.00%) of mycelial growth. Average inhibition was 52.49% with Pyraclostrobin 20% WG, 47.95% with Carbendazim 50% WP and 45.68% with Thiophanate methyl 70% WP.

Trichoderma asperellum recorded the lowest radial mycelial growth (20.16 mm) and the highest mycelial growth inhibition (77.60%), followed by T. harzianum (21.16 mm and 76.48%), Aspergillus niger (23.50 mm and 73.88%), T. hamatum (29.66 mm and 67.04%), T. koningii (24.33 mm and 72.96%), Bacillus subtilis (44.33 mm and 50.74%) and Pseudomonas fluorescens (48.33 mm and 46.30%), respectively.

Conclusion: Among the chemical treatments, Tebuconazole 25.9% EC, Propiconazole 25% EC, Hexaconazole 5% EC and Difenoconazole 25% EC, and among the biocontrol agents, Trichoderma asperellum, exhibited high antagonistic efficacy in vitro. These treatments warrant further evaluation for potential incorporation into integrated disease management strategies against Alternaria leaf blight of groundnut.