Induction of plant systemic defense by a gaseous compound against Pseudomonas syringae and aphid in cucumber in the open field

Abstract: Systemic acquired resistance (SAR) is a plant self-defense mechanism against a broad range of pathogens and insect pests. Among chemical SAR triggers, plant and bacterial volatiles are promising candidates due to high effectiveness and the fact of being cheap chemicals with relatively low concentrations compared to agrochemicals. However, before large scale application in agriculture to manage diseases, high evaporation rates after application, plant growth alteration, and inconsistent effectiveness need to be considered as major pitfall. In thisstudy, we provide a new evidence of volatile organic compound (VOC)-mediated SAR against both a bacterial angular leaf spot pathogen Pseudomonas syringae pv. lachrymans and a sucking insect aphid Myzus persicae in the open field without changing plant growth until harvesting. Unexpectedly, the drench of two VOCs, 3-pentanol and 2-butanone to cucumber seedlings caused significant increase of numbers of ladybird beetle that is known as a natural enemy of aphid. The defense-related gene, CsLOX was induced in volatile treatmented plants indicating to trigger oxylipin pathway responding in the emission of green leaf volatile that recruit the natural enemy. Our results demonstrate that VOCs are good resources to prevent plant diseases and insect damage by elicitation of SAR even in the open field.