Nitrogen fertilization amplifies stem borer susceptibility in rice: genotype-dependent trade-offs between yield and...

Rice (Oryza sativa L.) productivity is strongly influenced by nitrogen fertilization, genotype, and stem borer infestation. Understanding the interaction between nitrogen fertilization and genotype in determining host plant resistance and yield is essential for sustainable rice production. This study was conducted across the 2024 and 2025 growing seasons to evaluate the synergistic effects of rice genotypes and varying nitrogen application rates on insect infestation levels and agronomic performance. Four distinct genotypes were subjected to four nitrogen levels to assess their susceptibility to the rice stem borer, Chilo agamemnon Bles. Significant (P < 0.05) genotypic variation was observed regarding stem borer susceptibility. These results indicate that increasing nitrogen fertilization enhances grain yield while simultaneously increasing susceptibility to stem borer infestation, highlighting a potential trade-off between productivity and resistance. Across all genotypes, higher nitrogen applications (220 kg N/ha) significantly increased infestation percentages, while the lowest rates (55 kg N/ha) resulted in the least damage. Biochemical analysis revealed that the susceptible genotype (Super 302) possessed elevated concentrations of chlorophyll, total carbohydrates, and amines. In contrast, the more resistant genotypes (Giza 183 and GZ 10590) were characterized by significantly higher levels of protective phenols and silica. Regarding yield components, Giza 183 achieved the highest grain yields (averaging 11.03-11.06 t/ha), while Super 302 produced the lowest (9.88-9.93 t/ha). Although increased nitrogen rates up to 220 kg N/ha bolstered grain yields across all genotypes, they simultaneously exacerbated pest susceptibility. Notably, Giza 183 produced the highest number of panicles per hill at maximum N levels, whereas Super 302 was characterized by the earliest heading date and greatest plant height. These findings suggest that selecting for high silica and phenol content, combined with optimized nitrogen management, is critical for developing rice production systems that balance high productivity with robust insect resistance.