LAUSR

BACKGROUND Herbivores may influence each other directly and through plant mediated inter-specific interactions. The Asian citrus psyllid (Diaphorina citri Kuwayama) and citrus aphids are key pests that can co-exist on citrus, but their plant- mediated interaction between them is unknown. Here we investigated plant-mediated effect of two citrus aphid species, the polyphagous Aphis spiraecola Patch and the oligophagous Aphis (Toxoptera) citricidus (Kirkaldy) on the feeding behavior and reproduction of D. citri, and explored the underlying mechanisms. RESULTS In comparison with those on aphid free plants, D. citri had decreased reproduction and reduced phloem feeding on A. spiraecola pre-infested plants, while the reproduction and feeding efficiency were increased on A. citricida pre-infested plants. Jasmonic acid (JA) dependent defense was significantly activated by D. citri feeding on A. spiraecola pre-infested plants, but was suppressed by D. citri feeding on A. citricida pre-infested plants compared with that on aphid free plant. By contrast, only one tested marker gene in salicylic acid (SA) signaling was activated by D. citri feeding on A. spiraecola pre-infested plants. Furthermore, exogenous application of methyl jasmonate, but not SA, conferred resistance against D. citri in our citrus trials. CONCLUSION Our results indicate that pre-infestation by two citrus aphid species differentially altered D. citri induced citrus JA dependent defense, which resulted in different effect on subsequent D. citri performance. This article is protected by copyright. All rights reserved.