Biochemical Traits Related to Brown Planthopper Resistance in Rice Landraces

Nilaparvata lugens (Stål) is a major pest in rice, causing significant yield losses. This study evaluated 21 rice landraces and resistant varieties, including ASD7, Babawee, Chinasaba, IR36, ARC10550, IR64, IR-71033-121-15, Milyang, MUTNS1, OM4498, Pokkali, Ratu Heenati, RP 2068-18-3-5, Swarna, T12, CR-3006-8-2, CR-317, CR-805, and Salkathi along with resistant check PTB33 and susceptible check TN1, to investigate resistance mechanisms. Damage was assessed on a 1–9 scale: PTB33 and Salkathi were highly resistant (score 1, <8.5% damage), while TN1 and Swarna were fully susceptible (score 9, 100% damage).Resistant genotypes exhibited lower honeydew excretion (PTB33: 45.33 mm²; Salkathi: 52 mm²) and reduced nymphal survival (PTB33: 21%; Salkathi: 24.67%), compared to susceptible varieties (TN1: 197.33 mm²; 91.33%). Biochemical analysis revealed that BPH infestation reduced sugar and protein levels, with minimal losses in resistant genotypes (PTB33: 27.44% sugars, 8.95 % proteins) and significant reduction in TN1 (67.82% sugars, 53.82% proteins). Phenol levels increased post-infestation, with the highest increment in susceptible genotypes (TN1:52.19%; Swarna: 50.55%) and the lowest in resistant genotype (PTB33: 4.34%; Salkathi: 4.43%).These findings suggest that reduced sugar and protein levels and high phenol contentin plants contribute to antibiosis-based resistance in resistant genotypes. This study highlights the importance of resistant landraces in sustainable pest management for rice cultivation.