Impact of biocontrol agents on the physiological defence mechanisms of chilli against root-knot nematodes under organic mode of cultivation

Chili (Capsicum annuum) is a significant agricultural crop, widely cultivated for both culinary and medicinal purposes. India is the world’s largest producer, consumer, and exporter of chilies. However, the crop faces a significant threat from the root-knot nematode, Meloidogyne incognita, which damages plant roots and substantially reduces yields. To address this issue and support the growing demand for organic produce, a pot culture study was conducted organically during 2023-2024 at the College of Agriculture, Chiplima, Odisha. The study aimed to evaluate the effectiveness of different biocontrol agents against M. incognita using the susceptible chili variety 'Kashi Anmol'. The experiment was laid out in a Completely Randomized Design (CRD) with three replications. The egg-parasitic fungus Paecilomyces lilacinus was tested both individually and in combination with other biocontrol agents such as Trichoderma harzianum, Pseudomonas fluorescens, Bacillus thuringiensis, and organic amendments like mustard and neem oil cakes. The best results were achieved with the combined application of P. lilacinus (2.5 kg/ha) and T. harzianum (2.5 kg/ha), which significantly reduced root galls by 45.32%, egg masses by 62.85%, and soil nematode population by 40.27%. This treatment also resulted in a 67% increase in the number of fruits and a 48.61% increase in final yield compared to the untreated control. In contrast, P. lilacinus applied alone showed minimal improvement. The study also revealed a strong positive correlation between above-ground and below-ground plant growth parameters, while nematode infestation had a negative impact on both. These findings suggest that a healthier root system, supported by effective biocontrol agents, improves nutrient and water uptake, leading to better plant growth, enhanced photosynthesis, and higher yields.