Polyphagous aphids often have host-specialized lineages, and the mechanisms remain to be elucidated. The aphid Aphis gossypii has several host-specialized lineages including one specialized on Cucurbitaceae and one on Malvaceae. We found that the performance of Malvaceae lineage was poor on cucumbers, but significantly improved on cucumbers that were previously infested by Cucurbit lineage for 14 d. Following two-generation feeding experience on pre-infested cucumbers, Malvaceae lineage acquired the ability to use uninfested cucumbers. The pre-infestation largely decreased insect-negative metabolites such as cucurbitacins and phenols and increased insect-positive metabolites such as soluble sugars. The pre-infestation decreased the salicylic acid by 25.9% but increased the jasmonic acid by 1337% in cucumbers, which corresponded to expression of marker genes in phytohormone signaling pathways. Exogenous salicylic acid significantly decreased the performance improvement of Malvaceae lineage on pre-infested cucumbers, but exogenous jasmonic acid did not. Those results indicate that infestation by Cucurbit lineage altered the metabolism of cucumbers and interrupted the defense-associated phytohormones, from which we conclude that the disability in overcoming cucumber's defenses caused the incompatibility of Malvaceae lineage to cucumbers. The acclimation to cucumbers of Malvaceae lineage aphids may result from activation of some effector genes targeting cucumbers. Our findings provide new insights into the mechanisms of aphid host-specialization and new clues for preventing A. gossypii switching from Malvaceae hosts to cucurbits.

多食性蚜虫通常具有宿主特化谱系，其机制仍有待阐明。棉蚜（Aphis gossypii）有几个专门针对宿主的谱系，包括一种专门针对葫芦科植物和一种专门针对锦葵科植物。我们发现锦葵科谱系在黄瓜上的表现较差，但在之前被葫芦科谱系侵染14天的黄瓜上显着改善。经过两代对感染前黄瓜的喂养经验，锦葵科谱系获得了使用未感染黄瓜的能力。侵染前很大程度上减少了昆虫阴性代谢物，如葫芦素和酚类，并增加了昆虫阳性代谢物，如可溶性糖。侵染前黄瓜中的水杨酸减少了25.9%，但茉莉酸增加了1337%，这与植物激素信号通路中标记基因的表达相对应。外源水杨酸显着降低锦葵科谱系对预侵染黄瓜的性能改善，但外源茉莉酸则没有。这些结果表明，葫芦属谱系的侵染改变了黄瓜的新陈代谢，并中断了与防御相关的植物激素，由此我们得出结论，克服黄瓜防御能力的障碍导致了锦葵科谱系与黄瓜的不相容性。锦葵科蚜虫对黄瓜的适应可能是由于一些针对黄瓜的效应基因的激活所致。我们的研究结果为蚜虫寄主特化机制提供了新的见解，并为防止棉蚜从锦葵科寄主转向葫芦科寄主提供了新线索。