Amino acid profiles reveal the role of zucchini as a bridge host for Aphis gossypii transfer from cotton to cucumber

Background Aphis gossypii is a globally distributed pest, and its population dynamics are significantly influenced by host plants. This study investigated the nutritional mechanisms enabling zucchini to act as a “bridge host” for A. gossypii by comparing growth and amino acid metabolism on cotton, zucchini, and cucumber. Results Host plants significantly affected survival (zucchini > cotton > cucumber) and morphology, and aphids on zucchini and cucumber were larger than those on cotton, particularly in late adulthood. Principal component analysis revealed distinct metabolic profiles for zucchini-reared aphids. Zucchini leaves possessed the highest total amino acid content (1.9-2.3-fold higher than cotton and cucumber) and contained unique compounds such as citrulline and β-Alanine. Aphid amino acid accumulation patterns varied, with cucumber showing dramatic accumulation (7.58-fold increase) suggesting nutritional stress, while zucchini exhibited moderate accumulation with peak essential amino acids and cotton showed steady adaptation. Mantel tests confirmed that host plant species exerted a stronger influence on metabolic networks than developmental stage. Conclusions Zucchini facilitates host transfer by providing abundant nutritional substrates, effectively reducing the barrier for aphids shifting from cotton to cucumber. These findings offer a theoretical basis for nutrition-based pest management.