Phytohormone responses in pepper (Capsicum annuum L.) leaves under a high density of aphid infestation

The time course response of selected phytohormones has been evaluated in sweet pepper plants (Capsicum annuum L.) submitted to a high density (200 aphids/plant) of aphid (Myzus persicae Sulzer) infestation. Abscisic acid (ABA), salicylic acid (SA), indole‐3‐acetic acid (IAA), and jasmonates (JAs), including jasmonic acid (JA), jasmonoyl‐l‐isoleucine (JA‐Ile), and cis‐OPDA have been simultaneously identified and quantitated by UHPLC–MS/MS in pepper leaf tissue harvested at 3, 8 hours post‐infestation (hpi), 1, 2, 4 and 7 days post‐infestation (dpi). Infested plants showed a reduction in stem length at 7 dpi and in the number of leaves and leaf width from 4 dpi onwards. JA and JA‐Ile significantly increased very early (from 3 hpi) while SA only accumulated at 7 dpi. Despite the high density of infestation, the aphid‐induced accumulation of JAs was much lower than the burst typically induced by chewing herbivores. On the other side, ABA peaked in aphid‐infested plants at 2 and 4 dpi, while IAA content did not change significantly at any time point. Growth inhibition may be partially explained by the high levels of JAs found in aphid‐infested plants. The possibility that the obtained results support the hypothesis of the aphid manipulation of plant metabolism is discussed.This work was supported by the Ministerio de Economía y Competitividad of Spain, Project CGL2016-79054-R, by the University of Alicante grant UAFPU2013-5793 to VFO, and by the Ministry of Education, Youth and Sports of the Czech Republic – NPU I program with project LO1204. This work is part of VFO PhD Thesis