Two centuries of breeding has altered root system architecture of winter wheat

Crop selection and breeding has influenced plant phenotypes and genotypes. The necessary selection and breeding steps which resulted in today's cultivated plants have greatly reduced plant genetic diversity. Genetic bottlenecks in plant populations are thought to be a direct result of modern breeding programs. This study used a custom root phenotyping platform to characterize root system architecture (RSA) parameters in a diverse panel of winter wheat released between 1803 and 2002. Cultivars were grown in P-deficient phytagel and images captured through 360° using light tomography. RSA parameters were measured using GiA Roots software. Network length, width, surface area, and volume differed between old cultivars and both intermediate and modern cultivars. RSA did not vary between intermediate and modern cultivars. Growth rates of old cultivars were two times greater than both intermediate and modern cultivars regardless of dwarfing status. These results support the idea that plant breeding has had unintended effects on winter wheat root systems. The reduction of root system size and growth rates with increased year of release may have important implications for further breeding work related to nutrient use, drought tolerance, and C-sequestration. The faster root growth of older cultivars may also provide a breeding target for developing plants that establish and respond to stress faster, potentially improving crop resilience.