Medicinal Plant-Derived Copper Nanoparticles Effectively Manage Early Blight Disease in Tomato: An In vitro Study

Aims: Early blight of tomato (Solanum lycopersicum L.) incited by Alternaria solani is an economically important disease. This paper analyses the efficacy of copper nanoparticles (Cu-NPs) as an alternative to its existing management practices that predominantly rely on toxic fungicides which are potentially harmful to humans and the environment.

Study Design: The experiment was conducted in a completely randomized block design with 7 treatments viz. T1:Cu-NPs from tulsi leaves, T2:Cu-NPs from neem leaves, T3:Cu-NPs from bael leaves, T4: Cu-NPs from chemical A (prepared from 0.2 M of Cu(NO3)2.3H2O + 0.2 M Ascorbic acid), T5: Cu-NPs from chemical B (0.2 M Cu(NO3)2.3H2O + 0.2 M CuCl2 + 0.4 N NH4OH), T6: Carbendazim 50 WP as check and T7: Control. Each treatment was tested at two levels of in vitro concentrations (i.e. 300 and 500 ppm) and the treatments were replicated thrice.

Place and Duration of Study: Considering the importance of the disease and for developing an effective management strategy, the present study was carried out in the Department of Plant Pathology, College of Agriculture, Odisha University of Agriculture and Technology, Bhubaneswar during 2020-21.

Methodology: Stable Cu-NPs were synthesized through three green synthesis methods by using bael (Agel marmelos L.), tulsi (Ocimum sanctum L.), and neem (Azadirachta indica L.) leaves and two chemical synthesis methods (i.e. chemical A and B).

Results: The size (diameter) of the Cu-NPs from Agel marmelos, Ocimum sanctum, and Azadirachta indica were 427.4, 1,019, and 246.5 nm, and that from the aqueous solution reduction method and precipitation method were 1,537 and 867.8 nm, respectively. The synthesized Cu-NPs were evaluated against Alternaria solani at 300 and 500 ppm while Carbendazim 50 WP served as the standard check. The Azadirachta indica leaf-derived Cu-NPs at 300 and 500 ppm in the in vitro potato dextrose ager (PDA) medium exhibited the maximum mycelial growth inhibition of 60.24% and 75.9%, respectively. The size of Cu-NPs showed an inverse relation with the antifungal efficacy that indicated greater cellular penetration of smaller nanoparticles whereas much lower inhibition of mycelial growth in Carbendazim 50 WP as a check showed the lowest growth inhibition of 39.75% (300 ppm) and 59.03% (500 ppm).

Conclusion: The results thus indicated higher efficacy of nanoformulations at lower concentrations that can be effectively used for the development of new nano-based plant protection agents against the early blight of tomatoes.