Maize Voc Induction after Infection by the Bacterial Pathogen, Pantoea ananatis, Alters Neighbouring Plant Voc Emissions

Abstract

Plants induce volatile organic compounds (VOCs) after pathogen infection and exposure to a neighbouring infected plant. In a greenhouse, we measured VOCs from maize cv. ‘Prosna’ 3 or 7 d following foliar, or 42 d following soil, inoculation of Panteoa ananatis, a bacterial pathogen, as well as from uninfected neighbouring maize located 1 or 3 m from each infected plant treatment. We predicted the degree of VOC induction to be greatest 7 d post-foliar > 3 d post-foliar > 42 d post-soil inoculation; also, infected plant VOC induction > 1 m uninfected neighbour > 3 m uninfected neighbour. Maize infected by P. ananatis induced six common green leaf volatiles (GLVs), four common terpenes, and one common skikimic acid pathway derivative. Our results in general confirmed these two predictions, but there was an interaction. While 3 d post-foliar inoculated plants had greater VOC induction than an uninfected neighbour exposed 1 m from a 7 d post-foliar inoculated plant, 42 d post-soil inoculated plants had lower VOC induction than an uninfected neighbour exposed 1 m from a 3 d post-foliar inoculated plant. Thus, infected maize did not always emit higher VOC concentrations than uninfected maize exposed to an infected plant; it depended on the route of infection (foliar vs. soil inoculation) for the infected plant and which infected plant treatment was exposed to an uninfected plant. The VOC blend of maize cv. ‘Prosna’ after P. ananatis infection appears to be quantitatively different when compared to infection by a Fusarium spp. blend. The relevance of these maize VOC blend differences after infection by different pathogens needs to be studied, but our results suggest that maize responds with quantitatively different VOC blends depending on the infecting pathogen.