Evaluation of Resistance in Indian Rice to Root-Knot Nematode (Meloidogyne graminicola): Insights from Field and Histopathological Studies

Rice (Oryza sativa L.) is a staple crop for over half of the global population, yet its cultivation faces significant threats from biotic stresses, particularly root-knot nematodes (Meloidogyne spp.). Among these, M. graminicola poses a major challenge in rice-growing regions, leading to substantial yield losses. This study evaluated the resistance of 348 rice varieties to M. graminicola through controlled pot and field experiments over two years (2023 and 2024). Varieties were classified based on gall index, revealing a spectrum of susceptibility from highly susceptible to highly resistant. Notably, varieties such as JR-1124 and JR-403 exhibited high gall index, while others like RP-5219-9-7-3-2-1-1, NPT-10, MTU 1390 (IR17M1172), Kushiari, RP 6750-RMS-2-23-67-91, Sonkharchi, Sugandha-3, HRT-183, and HR-12 demonstrated significant resistance. Resistant rice genotypes exhibited significantly higher PAL, POX, and total phenolic content at all intervals, indicating a strong biochemical defense response against Meloidogyne graminicola. Advanced techniques, including confocal microscopy, revealed distinct histopathological responses to M. graminicola infection, with susceptible rice varieties exhibiting extensive giant cell formation and root tissue degradation, while a resistant variety displayed restricted giant cell development, enhanced callose deposition, and maintained vascular integrity-highlighting robust defense mechanisms against nematode invasion. The findings underscore the potential for breeding programs to enhance resistance traits in rice, contributing to sustainable agricultural practices and improved food security. As nematode populations evolve, ongoing research is essential to adapt breeding strategies and maintain effective management of this significant pest in rice production systems.