Both Jasmonic Acid- and Abscisic Acid-Mediated Signalling Pathways Regulate the Ovicidal Defence of Plants Against Phloem-Feeding Insects

Plants perceive signals associated with herbivore eggs and in response initiate ovicidal defence. However, which phytohormone pathways regulate this defence and which defensive compounds dominate it remains largely unknown. Here, we found that the hatching rate of eggs of white-backed planthopper (WBPH) Sogatella furcifera was significantly lower on a japonica rice variety P81 than an indica rice variety NB44. When infested by WBPH, P81 plants showed higher jasmonic acid (JA) and abscisic acid (ABA) responses than did NB44 plants; moreover, P81 plants produced the ovicidal compound benzyl benzoate and exhibited higher levels of some flavonoids, phenolamides, and volatiles than were found in NB44 plants. Impairing the ABA-signalling pathway, especially the JA-signalling pathway in P81 plants enhanced the survival of WBPH eggs. Decreasing levels of some flavonoids and phenolamides in P81 plants promoted WBPH egg survival. In vitro bioassays revealed that both naringenin and sakuranetin promote the ovicidal effect of benzyl benzoate on WBPH. The results demonstrate that JA- and ABA-signalling pathways jointly regulate the rice ovicidal defence against WBPH, and that benzyl benzoate, as well as some other compounds, such as naringenin and sakuranetin, contribute to the mortality of WBPH eggs.