Assessing the evolution of wheat grain traits during the last 166 years using archived samples

Abstract

The current study focuses on yield and nutritional quality changes of wheat grain over the last 166 years. It is based on wheat grain quality analyses carried out on samples collected between 1850 and 2016. Samples were obtained from the Broadbalk Continuous Wheat Experiment (UK) and from herbaria from 16 different countries around the world. Our study showed that, together with an increase in carbohydrate content, an impoverishment of mineral composition and protein content occurred. The imbalance in carbohydrate/protein content was specially marked after the 1960's, coinciding with strong increases in ambient [CO₂] and temperature and the introduction of progressively shorter straw varieties. The implications of altered crop physiology are discussed.

Figure 1

Trends in wheat yield and thousand kernel weight (TKW) of Broadbalk experiment from 1850 to 2016. Data are means. The dashed line represents the introduction of dwarf cultivars in 1968.

Figure 2

Wheat grain carbon isotope discrimination (Δ¹³C) of global (A) and Broadbalk experiment (B) samples. The dashed line corresponds to the separation between the [1850–1955] and [1965–2016] periods, based on the increase of [CO₂]. Data are means ± standard errors (n = 3–14). The same letters indicate no statistically significant differences among years (Fisher’s LSD, p ≥ 0.05).

Figure 3

Wheat grain starch content of global (A) and Broadbalk experiment (B) samples. The dashed line corresponds to the separation between the [1850–1955] and [1965–2016] periods, based on the increase of [CO₂]. Data are means ± standard errors (n = 3–14). The same letters indicate no statistically significant differences among years (Fisher’s LSD, p ≥ 0.05).

Figure 4

Wheat grain soluble sugar (sucrose, glucose and fructose) concentration of global (A,C,F) and Broadbalk experiment (B,D,G) samples. The dashed line corresponds to the separation between the [1850–1955] and [1975–2016] periods, based on the increase of [CO₂]. Data are means ± standard errors (n = 3–14). The same letters indicate no statistically significant differences among years (Fisher’s LSD, p ≥ 0.05).

Figure 5

Wheat grain protein content of global (A) and Broadbalk experiment (B) samples. The dashed line corresponds to the separation between the [1850–1955] and [1965–2016] periods, based on the increase of [CO₂]. Data are mean ± standard errors (n = 3–14). The same letters indicate no statistically significant differences among years (Fisher’s LSD, p ≥ 0.05).

Figure 6

Wheat grain carbon content of global (A) and Broadbalk experiment (B) samples. The dashed line corresponds to the separation between the [1850–1955] and [1965–2016] periods, based on the increase of [CO₂]. Data are means ± standard errors (n = 3–14). The same letters indicate no statistically significant differences among years (Fisher’s LSD, p ≥ 0.05).

Figure 7

Wheat grain C/N ratio of global (A) and Broadbalk experiment (B) samples. The dashed line corresponds to the separation between the [1850–1955] and [1965–2016] periods, based on the increase of [CO₂]. Data are means ± standard errors (n = 3–14). The same letters indicate no statistically significant differences among years (Fisher’s LSD, p ≥ 0.05).

Figure 8

Change in grain minerals concentration relative to [1850–1955] period of global (A) and Broadbalk experiment (B) samples. Data are means ± standard errors (n = 3–14). Statistically significant effects are indicated with *** for p < 0.001, ** for p < 0.01 and * for p < 0.05 (Fisher’s LSD).