Elevated CO2 Can Worsen Fusarium Head Blight Disease Severity in Wheat but the Fhb1 QTL Provides Reliable Disease Resistance

Abstract

Fusarium head blight (FHB) is a destructive fungal disease of wheat that causes significant economic loss due to lower yields and the contamination of grain with fungal toxins (mycotoxins), particularly deoxynivalenol (DON). FHB disease spread and mycotoxin contamination has been shown to worsen at elevated CO₂, therefore, it is important to identify climate-resilient FHB resistance. This work evaluates whether wheat with the Fhb1 quantitative trait locus (QTL), the most widely deployed FHB resistance locus in wheat breeding programs, provides reliable disease resistance at elevated CO₂. Near-isogenic wheat lines (NILs) derived from either a highly FHB susceptible or a more FHB resistant genetic background, with or without the Fhb1 QTL, were grown in growth chambers at ambient (400 ppm) and elevated (1000 ppm) CO₂ conditions. Wheat was inoculated with Fusarium graminearum and evaluated for FHB severity. At elevated CO₂, the NILs derived from more FHB-resistant wheat had increased disease spread, greater pathogen biomass and mycotoxin contamination, and lower rates of DON detoxification; this was not observed in wheat from a FHB susceptible genetic background. The Fhb1 QTL was not associated with increased disease severity in wheat grown at elevated CO₂ and provided reliable disease resistance.

Keywords: Fhb1; climate resilience; elevated CO2; food safety; fusarium head blight; mycotoxins; wheat.

Figure 1

Disease severity of Fusarium graminearum infected wheat heads as defined by(a) the area under the disease progression curve (AUDPC), (b) deoxynivalenol (DON) contamination, and (c) relative fungal biomass (Fg). Genotypes were derived from either a susceptible check (S) or a more resistant genetic background (M) and each either possessed the Fhb1 QTL, as indicated by a (+), or lacked the Fhb1 QTL, as indicated by a (−). Wheat was grown at either ambient (a[CO₂]) or elevated carbon dioxide concentrations (e[CO₂]). Error bars represent the standard error. Symbols (†, *, **, and ***) denote a statistically significant effect (p < 0.1, p < 0.05, p < 0.01, and p < 0.0001, respectively) of elevated CO₂ on AUDPC, DON, or Fg within a genotype, as determined by a non-parametric Van der Waerden test (AUDPC: n = 45 and DON and Fg: n = 15).

Figure 2

Wheat genotypes HR123 (M−) and HR 56 (M+) at one week post single floret inoculation of Fusarium graminearum. Both cultivars exhibit more severe FHB disease spread at elevated CO₂.

Figure 3

Disease severity in various wheat groups, as defined by (a) the area under the disease progression curve (AUDPC), (b) the relative fungal biomass in infected wheat heads (Fg), and (c) the accumulation of deoxynivalenol (DON) in wheat heads at either ambient (a[CO₂]) or elevated carbon dioxide concentrations (e[CO₂]). Error bars represent standard error. Different letters denote statistically significant differences as determined by a non-parametric Wilcoxon/Kruskal–Wallis for multiple pairwise comparisons (AUDPC: n = 135; DON and Fg: n = 45).

Figure 4

The percentage of deoxynivalenol-3-glucoside (D3G), on a molar basis, in total measured trichothecenes in wheat cultivars (a) and by group (b) at either ambient (a[CO₂]), or elevated carbon dioxide concentrations (e[CO₂]). Error bars represent standard error. Symbols (†, *, **) denote a statistically significant effect of elevated CO₂ on disease characteristics within a group (p < 0.1, p < 0.05; respectively), as determined by a non-parametric Van der Waerden test ((a): n = 15). Different letters denote statistically significant differences as determined by a non-parametric Wilcoxon/Kruskal–Wallis for multiple pairwise comparisons ((b): n = 45).

Figure 5

Correlations between the percentage of deoxynivalenol-3-glucoside (D3G) and FHB disease metrics: (a) area under the disease progression curve (AUDPC), (b) relative Fusarium graminearum biomass (Fg), and (c) deoxynivalenol (DON) contamination at either ambient (a[CO₂]) or elevated carbon dioxide concentrations (e[CO₂]). Significant correlations are highlighted in bold text (α = 0.05).