Empirical Selection of Cultivated Oat in Response to Rising Atmospheric Carbon Dioxide

Abstract

Carbon dioxide is a principle resource for plant growth; as such, the ongoing increase in its concentration may allow breeders to begin selecting for optimal cultivars among current crop lines. Such a program may not be necessary, however, if breeders have, by empirical selection, already chosen the most responsive cultivars. To test this hypothesis, we examined the growth and vegetative characteristics of individual plants of cultivated oat (Avena sativa L.) from seven geographical locations to CO2 concentration ([CO2]) increases that corresponded roughly to the [CO2] from the 1920s, the current [CO2], and the [CO2] projected for the middle of this century (300, 400, and 500 μmol mol−1, respectively). In contrast to our predictions, newer lines were less responsive than older lines to rising [CO2] in terms of both leaf area and tiller number. A comparison of phenotypic variability indicated that for almost all measured parameters, older lines had a greater degree of intraspecific variability (i.e., newer lines were more uniform). As a consequence, a number of CO2‐sensitive lines among older cultivars were identified with respect to parameters such as vegetative biomass or tiller production. Our results suggest that for oat: (i) newer lines are not intrinsically more responsive to rising CO2 levels than older lines; and (ii) phenotypic homogenization among modern lines could hamper efforts to identify desirable characteristics associated with CO2 responsiveness.