Partial acquisition shifts and trait variation drive modular resource-use differentiation in naked oat.

Understanding how crop breeding alters plant resource-use strategies is essential for improving yield formation in increasingly variable climates. Although the plant economics spectrum is widely used to describe plant functional strategies in natural ecosystems, its applicability to intensively bred crop species remains unclear. This study compared four traditional landraces released before the 1950s and four modern naked oat cultivars released after the 2000s in a field experiment conducted in Yunnan, China, during the 2024 and 2025 growing seasons. Modern cultivars exhibited a partial shift toward an acquisitive strategy, with higher leaf nitrogen concentrations and higher nitrogen-to-phosphorus ratios. Despite significantly higher precipitation and improved growth performance (yield and biomass) in 2025, the plant economics spectrum strategy remained stable across all cultivars. This decoupling between resource availability and strategy indicates that naked oat retains a conserved resource-use framework shaped by its origin in marginal lands. Yield gains in modern cultivars (averaging 87.9% higher than landraces) were strongly correlated with elevated harvest index (r = 0.80, P < 0.001) rather than total aboveground biomass. Despite these changes, breeding did not exhibit a coordinated shift across all functional traits. The log response ratio (lnRR) of trait changes between landraces and modern cultivars showed no significant association with plant economics spectrum scores, indicating that breeding selectively targeted specific acquisitive traits rather than shifting the entire trait spectrum. These findings highlight that contemporary naked oat breeding integrates yield improvements with residual conservative traits, indicating an adaptive trade-off in performance under variable agroecological conditions. Future breeding efforts should focus on resilient-acquisitive ideotypes (crop architectures combining targeted acquisitive traits with conserved stress-resilience mechanisms) that sustain resource-use efficiency while enhancing environmental robustness to stabilize yields in the variable, low-input agroecosystems where naked oat is predominantly cultivated.