One of the key concepts in functional ecology is the notion of trade-offs in functional traits. Traits beneficial in one environment might be detrimental in another and vice versa. In cultivated crop systems high yielding varieties generally show a far stronger decrease in productivity under adverse conditions than their wild progenitors. This raises the question of which suite of traits is beneficial under optimal and adverse conditions and whether there are inherent trade-offs in performance depending on traits. By using inbred lines of cultivated sunflower as a model we investigated whether there is a genetic basis to trade-offs in performance and whether traits can be used to predict that trade-off
To address this question we evaluated a morphologically and genetically diverse population of 287 inbred cultivated sunflower genotypes, suitable for genome-wide association studies. Plants were grown in 7.5L pots with either 80g (high nutrients) or 8g (low nutrients) of slow release fertilizer (NPK 15-9-12) and harvested at budding (R2 stage). At harvest, we measured several morphological traits, biomass accumulation, biomass allocation to leaves, stem and roots, plant height, specific leaf area, specific root length/volume, as well as leaf chemical traits, nitrogen content and chlorophyll content.
All genotypes responded to nutrient stress with decreased above ground biomass (mean 40.6% decrease). However, higher performance in high nutrients did not necessarily predict poorer performance in low nutrients. Based on above-ground biomass ranking, genotypes could be categorized into four main groups, resistant (consistently high ranking), susceptible (large rank decrease), tolerant (large rank increase) and feeble (consistently low ranking). Principal component analysis of 23 biomass independent traits of 20 genotypes clearly assignable to each group definition showed groups separating along PC1 (explaining 23.7% at high nutrients, 33.3% at low nutrients). Genotypes PC1 score at high nutrients was a good predictor of above-ground biomass at high nutrients (R2:0.85) but less so at low nutrients (R2:0.52), PC1 score at low nutrients mirrored this, indicating shifts in beneficial traits.
These results suggest that in cultivated sunflower there is no inherent trade-off in nutrient stress tolerance. Moreover, performance is linked to different traits in treatments. Ongoing genomic analysis focuses on determining the genetic basis of these traits under high and low nutrient conditions. The lack of an inherent trade-off to nutrient stress resistance highlights the potential for breeding more resilient crops, easing demands on food production due to rising population levels and climate change.