Reduced response diversity does not negatively impact wheat climate resilience

Kahiluoto et al. (1) assert that climate resilience in European wheat has declined due to current breeding practices. To support this alarming claim, the authors report yield variance data indicating increasingly homogeneous responses to climatic fluctuations in modern wheat cultivars. They evaluated “response diversity,” a measure of responses to environmental change among different species jointly contributing to ecosystem functions (2). We question the suitability of this measure to describe agronomic fitness in single-cultivar wheat cropping systems. Conclusions are made about “long-term trends,” which in fact span data from barely a decade, corresponding to the duration of a single wheat breeding cycle. The authors furthermore acknowledge increasing climate variability during the study period, confounding their analysis of climate response in the same time span.

The underlying data are not published with the manuscript. Thus, the assertion that there is “no inherent trade-off between yield potential and diversity in weather responses” (1) cannot be verified. Inexplicably, the analysis and conclusions ignore absolute yields, which increase over time through breeding (3–6). Furthermore, incompatible data from completely different ecogeographical forms and species of wheat are apparently considered together, and the dataset is strongly biased toward a few small countries with minimal wheat production and narrow agroclimatic gradients.

The study assumes that increased response diversity among different cultivars is associated with yield stability. In contrast, the common, agronomic definition of yield stability refers to the ability of a single cultivar to stably perform well in diverse environments, without excessive responses to fluctuating conditions. Response diversity measures that ignore absolute yield do not support statements about food security or financial returns to farmers.

Cultivar yield potential, stability, and adaptation are enhanced by multienvironment selection over long breeding time frames, encompassing climate fluctuations and a multitude of other relevant environmental variables. Translation to on-farm productivity is promoted by national registration trials and extensive, postregistration regional variety trials in diverse environments. The unsurprising conclusion that planting multiple cultivars enhances overall production stability mirrors longstanding farming recommendations and practice (7). The availability of robust performance data from a broad range of high-performing cultivars enables European farmers to manage their production and income risks.

Kahiluoto et al. (1) speculate about “genetic erosion” of modern cultivars due to a “lack of incentives for breeders to introduce divergent material.” To substantiate these claims, the authors cite inadequate genetic data from non-European durum wheat (8), while explicitly dismissing clearly opposing findings about genetic diversity in European bread wheat (9). Short-term reductions in response diversity in five countries were misleadingly reported as a “long-term decline” in climate resilience in “most European countries,” although six out of seven countries with sufficient data showed no long-term decline. The article from Kahiluoto et al. and the misrepresentation of its results distorts decades of rigorous, successful breeding for yield potential and stability in European wheat and misleads farmers with pronouncements that are not supported by relevant data.