Biochemical Basis of Resistance in Oryza rufipogon (Wild rice) against Meloidogyne graminicola and Drechslera oryzae in Punjab

Rice (Oryza sativa L.), a staple food for over half of the global population, faces severe yield losses due to biotic stresses, notably the rice root knot nematode (Meloidogyne graminicola) and brown leaf spot pathogen (Drechslera oryzae). These pathogens significantly affect root function and overall plant health. This study investigates the biochemical basis of resistance in Oryza rufipogon (wild rice) accessions against these pathogens by analyzing key defense-related enzymes and compounds. Two resistant and two susceptible accessions of O.rufipogon were evaluated against M. graminicola alone, along with accessions resistant and susceptible to both pathogens. Biochemical parameters including PAL (phenylalanine ammonia lyase), TAL (tyrosine ammonia lyase), peroxidase, total phenols, ortho-dihydroxy phenols and total proteins were quantified post-inoculation. There were significantly higher activity of all enzymes and phenolic compounds in resistant accessions compared to susceptible ones under both single and combined pathogen inoculations. Increased activity of PAL and TAL suggests enhanced lignin biosynthesis, aiding structural defense. Elevated peroxidase activity indicates a stronger reactive oxygen species (ROS) detoxification response, while higher phenol levels point to the activation of redox-based defenses. The findings suggest that resistance in O. rufipogon is strongly associated with upregulation of specific biochemical pathways and can serve as a foundation for developing resistant rice cultivars. This study provides valuable insights into host-pathogen interactions and the role of biochemical markers in rice defense mechanisms.