Article,
Elevated CO2 alters grain quality of two bread wheat cultivars grown under different environmental conditions
AGRICULTURE ECOSYSTEMS & ENVIRONMENT, (March 2014)
DOI: \%7B10.1016/j.agee.2013.11.023\%7D
Abstract
Bread wheat (Triticum aestivum L cv. Yitpi and cv. Janz) was grown under field conditions in the Australian Grains Free-Air CO2 Enrichment (AGFACE) facility. Ambient CO2 (aCO2, similar to 384 mu mol mol(-1)) and elevated CO2 (eCO2, similar to 550 mu mol mol(-1)) were combined with two soil water levels (rain-fed and irrigated) and two times of sowing (TOS) in three consecutive years to provide six environments (2007-TOS1, 2007-TOS2, 2008-TOS1, 2008-TOS2, 2009-TOS1, 2009-TOS2). Grain samples were assessed for a range of physical, nutritional and dough rheological properties. The effect of eCO2 on thousand grain weight (TGW) was significantly different in each growing environment: TGW was significantly increased under eCO2 only at 2007-TOS2 (by 5\%), 2009-TOS1 (by 5\%) and 2009-TOS2 (by 15\%) but not significantly changed under other conditions. The magnitude of reduction of grain protein concentration at eCO2 differed among the growing environments but was highly correlated with the percentage yield stimulation under eCO2 (r(2) = 0.91) suggesting that grain protein concentration under eCO2 was diluted by increased yield. Across all treatments, grain nutrient concentration was significantly reduced by eCO2 for Fe (3.9\%, 6.2\%), Cu (2.2\%, 3.4\%), Zn (5.9\%, 5.7\%), Ca (5.6\%, 7.3\%), Mg (5.6\%, 5.8\%), Na (21.2\%, 30.4\%), S (4.4\%, 4.4\%), P (4.1\%, 3.2\%) in cv. Yitpi and Janz, respectively. Effects of eCO2 on grain Zn, Mg and Na concentrations were dependent on the growing environment. Relative reduction of grain S, Fe, Mg, Zn, P at eCO2 were significantly correlated with grain yield stimulation at eCO2. Reductions of these nutrients under eCO2 were not fully explained by biomass dilution as the relationships differed for each nutrient. Under eCO2, flour yield of cv. Janz was increased but that of cv. Yitpi was not changed. Even though grain protein concentrations of both cultivars were similar at eCO2, bread volume as inferred indirectly by dough rheology parameters was 12\% greater for cv. Janz (185 +/- 5 cm(3)) than cv. Yitpi (162 +/- 4 cm(3)) at eCO2. This disparity may be related to the compositional changes in wheat flour protein at eCO2, suggesting that future breeding and adaptation strategies to improve the grain quality under eCO2 should consider the prevailing hydro-thermal conditions. (C) 2013 Published by Elsevier B.V.
