Interactive Effects of Elevated [CO2] and Drought on the Maize Phytochemical Defense Response against Mycotoxigenic Fusarium verticillioides

Abstract

Changes in climate due to rising atmospheric carbon dioxide concentration ([CO2]) are predicted to intensify episodes of drought, but our understanding of how these combined conditions will influence crop-pathogen interactions is limited. We recently demonstrated that elevated [CO2] alone enhances maize susceptibility to the mycotoxigenic pathogen, Fusarium verticillioides (Fv) but fumonisin levels remain unaffected. In this study we show that maize simultaneously exposed to elevated [CO2] and drought are even more susceptible to Fv proliferation and also prone to higher levels of fumonisin contamination. Despite the increase in fumonisin levels, the amount of fumonisin produced in relation to pathogen biomass remained lower than corresponding plants grown at ambient [CO2]. Therefore, the increase in fumonisin contamination was likely due to even greater pathogen biomass rather than an increase in host-derived stimulants. Drought did not negate the compromising effects of elevated [CO2] on the accumulation of maize phytohormones and metabolites. However, since elevated [CO2] does not influence the drought-induced accumulation of abscisic acid (ABA) or root terpenoid phytoalexins, the effects elevated [CO2] are negated belowground, but the stifled defense response aboveground may be a consequence of resource redirection to the roots.

Discovery, Biosynthesis and Stress-Related Accumulation of Dolabradiene-Derived Defenses in Maize

“…ZmAN2 was first described in a differential display analysis of highly elicited transcripts following F. graminearum challenge of maize silks (Harris et al, 2005). Following the first description of ZmAN2, pathogen-elicited transcripts have been observed and reported in a large number of maize studies with diverse microbes Schmelz et al, 2011Schmelz et al, , 2014van der Linde et al, 2011;Vaughan et al, 2014;Christie et al, 2017). The nearly ubiquitous presence of ZmAN2 as a pathogen defense transcript marker is consistent with the essential biosynthetic role in the modular formation of multiple specialized diterpenoid metabolites, including not only A-and B-series kauralexins but also dolabralexins.…”

Fighting on two fronts: Elevated insect resistance in flooded maize

“…The problem of combined abiotic and biotic stresses is complicated by the fact that the response of maize to an abiotic stress can alter its ability to respond to biotic attack. For example, elevated atmospheric carbon dioxide levels increases the susceptibility of maize to the fungal pathogen Fusarium verticillioides (Vaughan et al, ). Furthermore, this susceptibility is amplified if the plants are exposed to both elevated carbon dioxide and drought (Vaughan et al, ).…”

Rising atmospheric CO2 concentration may imply higher risk of Fusarium mycotoxin contamination of wheat grains

“…(Magan et al 2011, Juroszek andTiedemann 2013). Research on maize found that elevated CO2 level increased susceptibility to Fusarium verticillioides proliferation with no change in mycotoxin levels (Vaughan et al 2014). In wheat, an increase in Fusarium pseudograminearum biomass and/or in stem browning was found in response to elevated CO2 in some situations, depending on the varieties (Melloy et al 2010(Melloy et al , 2014.…”