Divergent Cross-Adaptation of Herbicide-Treated Wheat and Triticale Affected by Drought or Waterlogging

Abstract

Widely used agrochemicals that do not exert negative effects on crops and selectively target weeds could influence plant resilience under unfavorable conditions. The cross-adaptation of wheat (Triticum aestivum L.) and triticale (×Triticosecale Wittm.) exposed to two environmental abiotic stressors (drought and waterlogging) was evaluated after treatment with a selective herbicide (Serrate^®, Syngenta). The ambivalent effects of the herbicide on the two studied crops were particularly distinct in waterlogged plants, showing a significant reduction in wheat growth and better performance of triticale individuals exposed to the same combined treatment. Histochemical staining for the detection of reactive oxygen species (ROS) confirmed that the herbicide treatment increased the accumulation of superoxide anion in the flooded wheat plants, and this effect persisted in the younger leaves of the recovered individuals. Comparative transcript profiling of ROS scavenging enzymes (superoxide dismutase, peroxidase, glutathione reductase, and catalase) in stressed and recovered plants revealed crop-specific variations resulting from the unfavorable water regimes in combination with the herbicide treatment. Short-term dehydration was relatively well tolerated by the hybrid crop triticale and this aligned with the considerable upregulation of genes for L-Proline biosynthesis. Its drought resilience was diminished by herbicide application, as evidenced by increased ROS accumulation after prolonged water deprivation.

Keywords: ROS; Serrate®; antioxidant enzymes; cereal crops; cross-adaptation; water stress.

Figure 1

Growth parameters: (a) fresh weight (FW), (b) dry weight (DW), and (c) shoot length of control (solid black line), herbicide-treated (dashed black line), drought-stressed (solid red line), waterlogged plants (solid blue line), and plants subjected to combined stress treatments (HD—herbicide and drought, designated by dashed red line; HW—herbicide and waterlogging, designated by dashed blue line). Results from four sampling points are represented: 72 h after herbicide application (day 3, white area on the graphs); 96 h of stress (day 7, light-gray area), 168 h of stress (day 10, dark-gray area), and after 96 h of recovery (day 14, light-green area). The bars represent the standard deviation (SD, n ≥ 15). Asterisks designate statistically significant differences among the treatment groups at each sampling point (at p < 0.05; one-way ANOVA with Tukey HSD analyses that are shown in Tables S1 and S2).

Figure 2

Histochemical staining for the detection of ROS in the last fully expanded true leaf of wheat control plants (C) and plants subjected to a standard dose of a selective herbicide (H), drought (D) or waterlogging (W), and their combinations (HD and HW, respectively). The second leaf (L2) was used at each sampling point, and the third leaf (L3) was included at the recovery stage. (a) NBT staining was applied for the detection of superoxide anion (O₂^●−), and (b) hydrogen peroxide (H₂O₂) accumulation was detected via DAB staining. The graphs represent the optical density (OD) with the calculated standard errors (SE, n ≥ 3). The asterisks (*) designate statistical significance between the compared experimental groups (p < 0.05, one-way ANOVA).

Figure 3

Histochemical staining for the detection of ROS in the last fully expanded true leaf of triticale control plants (C) and plants subjected to a standard dose of a selective herbicide (H), drought (D) or waterlogging (W), and their combinations (HD and HW, respectively). The second leaf (L2) was used at each sampling point, and the third leaf (L3) was included at the recovery stage. (a) NBT staining was applied for the detection of superoxide anion (O₂^●−), and (b) hydrogen peroxide (H₂O₂) accumulation was detected via DAB staining. The graphs represent the optical density (OD) with the calculated standard errors (SE, n ≥ 3). The asterisks (*) designate statistical significance between the compared experimental groups (p < 0.05, one-way ANOVA).

Figure 4

Transcript profiling of genes coding for T. aestivum Cu/ZnSOD, FeSOD, and MnSOD genes in wheat (a) and triticale (b) leaves derived from control (C), herbicide-treated (H), drought-stressed (D), waterlogged plants (W), and plants subjected to combined stress treatments (HD—herbicide and drought; HW—herbicide and waterlogging) at different sampling points (96 h of stress, 168 h of stress, after 96 h of recovery). Values are means of three biological repeats (n = 3) ± SD; n.d.—“not detected”. The lowercase letters designate statistically significant differences among the treatments at each sampling point (p < 0.05, one-way ANOVA).

Figure 5

Transcript profiling of T. aestivum catalase (CAT-3 and CATA) and peroxidise genes (POX2 and POD1) in wheat (a) and triticale (b) leaves derived from control (C), herbicide-treated (H), drought-stressed (D), waterlogged plants (W), and plants subjected to combined stress treatments (HD—herbicide and drought; HW—herbicide and waterlogging) at different sampling points (96 h of stress, 168 h of stress, after 96 h of recovery). Values are means of three biological repeats (n = 3) ± SD; n.d.—“not detected”. The lowercase letters designate statistically significant differences among the treatments at each sampling point (p < 0.05, one-way ANOVA).

Figure 6

Transcript profiling of T. aestivum glutathione reductase gene (GR) in wheat and triticale leaves derived from control (C), herbicide-treated (H), drought-stressed (D), waterlogged plants (W), and plants subjected to combined stress treatments (HD—herbicide and drought; HW—herbicide and waterlogging) at different sampling points (96 h of stress, 168 h of stress, after 96 h of recovery). Values are means of three biological repeats (n = 3) ± SD; n.d.—“not detected”. The lowercase letters designate statistically significant differences among the treatments at each sampling point (p < 0.05, one-way ANOVA).

Figure 7

Transcript profiling of T. aestivum delta-1-pyrroline-5-carboxylate synthase (P5CS) and pyrroline-5-carboxylate reductase (P5CR) genes in wheat (a) and triticale (b) leaves derived from control (C), herbicide-treated (H), drought-stressed (D), waterlogged plants (W), and plants subjected to combined stress treatments (HD—herbicide and drought; HW—herbicide and waterlogging) at different sampling points (96 h of stress, 168 h of stress, after 96 h of recovery). Values are means of three biological repeats (n = 3) ± SD; n.d.—“not detected”. The lowercase letters designate statistically significant differences among the treatments at each sampling point (p < 0.05, one-way ANOVA).