Can a wheat cultivar with high transpiration efficiency maintain its yield advantage over a near-isogenic cultivar under elevated CO2?

Abstract

This study investigated whether yield advantages of the wheat cultivar ‘Drysdale’ (selected for high transpiration efficiency) over recurrent parent ‘Hartog’ (low transpiration efficiency) are maintained under future atmospheric CO2. Growth, yield and yield components at three developmental stages (stem elongation, anthesis, maturity) were evaluated at two CO2 concentrations (ambient, a[CO2], ∼390μmolmol−1 and elevated, e[CO2], ∼550μmolmol−1). Growth under e[CO2] stimulated yield and above ground biomass on average by ∼18%. ‘Hartog’ compared to ‘Drysdale’ had significantly greater crop growth rate (∼14%), above ground biomass (∼15%), leaf area index (∼25%) and tiller numbers (∼16%) during early development (stem elongation). ‘Hartog’, however, lost this initial growth advantage over ‘Drysdale’ until anthesis when ‘Drysdale’ had more green leaf mass (∼15%) and greater spike (∼8%) and tiller (∼11%) numbers, particularly when grown under e[CO2]. At maturity, this resulted in a yield advantage of ∼19% of ‘Drysdale’ over ‘Hartog’ when grown under e[CO2] but only of ∼2% under a[CO2]. We suggest that wheat cultivars selected for superior transpiration efficiency will remain successful in a high [CO2] world. Evidence from this study even indicates that such cultivars may confer future advantage in some environments where this is not evident under current [CO2].