Suppression of Tomato Leaf Curl Virus in Tomato with Enhanced Growth, Yield and Fruit Quality by Phyllanthus niruri and Boerhavia diffusa under Field Conditions

Abstract

Aims: To evaluate promising antiviral botanicals such as Phyllanthus niruri and Boerhavia diffusa at low concentrations for managing tomato leaf curl disease (ToLCD) in tomato plants under pot culture and field conditions. Study Design: Sequential pot culture and field experiments were conducted using a completely randomised design (CRD) in pot culture and a randomised block design (RBD) in field studies to evaluate pre- and post-treatment of promising antiviral botanicals for the management of ToLCD. Place and Duration of Study: Pot experiments were conducted at the College of Agriculture, Vellayani, and field experiments were conducted at the College of Agriculture, Vellayani, and Coconut Research Station, Balaramapuram, Kerala, during summer and rabi seasons in 2023 and 2024. Methodology: P. niruri and B. diffusa shoot extracts at 0.25, 0.5, 1, 5 and 10 per cent (w/v) were evaluated through pre- and post-application to tomato plants inoculated with tomato leaf curl virus (ToLCV) by wedge grafting using infected scions of disease grade 2. Disease incidence (DI), vulnerability index (VI), virus accumulation, plant growth, chlorophyll content, yield and fruit quality were assessed. Results: Pre-application of 1 per cent P. niruri reduced DI from 100 to 57.69 per cent and VI from 68.34 to 33.12, representing reductions of 42.31 and 51.54 per cent, respectively, compared with the ToLCV control plants. One per cent B. diffusa reduced DI and VI by 34.62 and 44.02 per cent, respectively. Post-application of 1 per cent P. niruri reduced DI and VI by 34.62 and 41.70 per cent, respectively. One per cent botanical preparations resulted in reductions in DI and VI comparable to those obtained with the 5 and 10 per cent preparations; therefore, 1 per cent was considered practically and economically feasible. Serological and molecular analyses indicated reduced virus accumulation in the treated plants. Under field conditions, pre-application of 1 per cent P. niruri reduced DI by 22.72 and 21.95 per cent and VI by 33.07 and 35.87 per cent during summer and rabi, respectively. Botanical treatments also improved chlorophyll content, growth, yield and fruit quality, with the botanicals increasing the number of fruits per plant by 40.5 per cent compared with the control. Conclusion: P. niruri and B. diffusa shoot extracts at 1 per cent could significantly reduce the DI and VI of ToLCD and could be used as a potential botanical component in the integrated management of the disease, with pre-application providing greater disease suppression than post-application.