Effects of elevated [CO₂] on maize defence against mycotoxigenic Fusarium verticillioides

Abstract

Maize is by quantity the most important C4 cereal crop; however, future climate changes are expected to increase maize susceptibility to mycotoxigenic fungal pathogens and reduce productivity. While rising atmospheric [CO2] is a driving force behind the warmer temperatures and drought, which aggravate fungal disease and mycotoxin accumulation, our understanding of how elevated [CO2] will effect maize defences against such pathogens is limited. Here we report that elevated [CO2] increases maize susceptibility to Fusarium verticillioides proliferation, while mycotoxin levels are unaltered. Fumonisin production is not proportional to the increase in F. verticillioides biomass, and the amount of fumonisin produced per unit pathogen is reduced at elevated [CO2]. Following F. verticillioides stalk inoculation, the accumulation of sugars, free fatty acids, lipoxygenase (LOX) transcripts, phytohormones and downstream phytoalexins is dampened in maize grown at elevated [CO2]. The attenuation of maize 13-LOXs and jasmonic acid production correlates with reduced terpenoid phytoalexins and increased susceptibility. Furthermore, the attenuated induction of 9-LOXs, which have been suggested to stimulate mycotoxin biosynthesis, is consistent with reduced fumonisin per unit fungal biomass at elevated [CO2]. Our findings suggest that elevated [CO2] will compromise maize LOX-dependent signalling, which will influence the interactions between maize and mycotoxigenic fungi.Elevated [CO2] increases maize susceptibility to Fusarium verticillioides proliferation but mycotoxin levels are unaltered. The attenuation of maize 13-LOXs and JA production correlates with reduced terpenoid phytoalexins and increased susceptibility. Furthermore, the attenuated induction of 9-LOXs, which have been suggested to stimulate mycotoxin biosynthesis, is consistent with reduced fumonisin per unit fungal biomass at elevated [CO2].

Coffee growth, pest and yield responses to free-air CO2 enrichment

“…In any case, in other pathosystems, fungi have tended to be less affected by enhanced atmospheric [CO 2 ] than have the plant hosts (Chakraborty and Datta 2003). Vaughan et al (2014), for example, found that maize plants grown in elevated [CO 2 ] became more susceptible to Fusarium verticilioides, but the production of mycotoxins was unaffected by [CO 2 ].…”

Synthesis and Functions of Jasmonates in Maize

“…JA is also required for immunity against another common opportunistic soil-borne fungus, F. verticillioides , as the opr7opr8 mutants succumb to mesocotyl inoculation as rapidly as 8 h post-infection by this pathogen [76]. In another study, JA accumulation and JA biosynthetic gene induction correlated with increased resistance against F. verticillioides stalk rot in a CO 2 -dependent manner [148]. A recent genome-wide association study of maize infected by A. flavus identified the JA pathway as the most impacted between resistant and susceptible genotypes [149].…”

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

“…As a consequence, the ISI-MIP protocol has been conducted with and without accounting for CO 2 -fertilization effects (further referred to as the CO 2 -ensemble and noCO 2 -ensemble, respectively). Recent findings also underline the importance of elevated temperatures and heat extremes (Gourdji et al, 2013;Deryng et al, 2014), ozone concentrations (Tai et al, 2014) as well as the potential of increasing susceptibility to disease as a consequence of elevated CO 2 levels (Vaughan et al, 2014) for agricultural yields, which may counteract potential yield gains by CO 2 -fertilization (Porter et al, 2014). Results for the CO 2 and noCO 2 -ensembles are presented separately, showing the range of potential manifestations and the additional risks of regional yield reductions, if effects of CO 2 -fertilization turn out to be lower than estimated by the model ensemble.…”