Multi-omics combined life table analysis reveals the impact of nitrogen application rates on cotton fitness and Aphis gossypii population dynamics

Excessive nitrogen fertilizer application in cotton fields not only leads to various forms of soil and water pollution but also elevates the risk of pest outbreaks, especially A. gossypii . However, the molecular mechanisms by which varying nitrogen ratios regulate crop physiological traits and subsequently influence insect population parameters remain poorly understood. In this study, we combined physiological assays, life table analysis, and multi-omics techniques to systematically investigate the tripartite interactions among nitrogen fertilizers, cotton plants, and cotton aphids. Notably, a medium nitrogen level (0.9 g/kg) exerted a paradoxical effect on A. gossypii : it significantly lowered net reproductive rate ( R₀ ) and total fecundity, yet simultaneously yielded the highest intrinsic rate of increase (r). Integration of multi-omics data with life table analysis revealed that the significant up-regulation of signaling pathways (Plant-pathogen interaction, Glycerolipid metabolism, ABC transporters) and metabolites (Phenolic acids, organic acids) likely constitutes key inhibitory factors leading to the decrease in the R 0 value of cotton aphids and the increase in the r . Furthermore, we identified that significantly upregulated differentially expressed genes (DEGs) and metabolites in cotton under medium-nitrogen conditions reduce A. gossypii reproduction potentiality by modulating pest key signaling pathways, including Lysosome, Antigen processing and presentation, NOD-like receptor signaling, and Glycosphingolipid biosynthesis.This study elucidates the cotton can modulate the population dynamics of A. gossypii by altering physiological and metabolic traits under varying nitrogen fertilization levels, thereby informing the optimization of integrated pest management strategies for cotton aphids under nitrogen-regulated conditions. • The life table analysis showed that A. gossypii exhibited the lowest reproduction rate (R₀) and fecundity values in the medium-nitrogen groups. • Multi-omics and life table data revealed the mechanism underlying the decline in the reproductive potential of aphid in the medium-N groups. • Medium-N groups induce high expression of cotton genes/metabolites, suppressing aphid reproductive potential.