A wheat/rye polymorphism affects seminal root length and yield across different irrigation regimes

The introgression of a small segment of wheat (Triticum aestivum L.) chromosome arm 1BS in the distal region of the rye (Secale cereale L.) 1RS.1BL arm translocation in wheat (henceforth 1RS^RW) was previously associated with reduced grain yield, carbon isotope discrimination, and stomatal conductance, suggesting reduced access to soil moisture. Here we show that lines with the normal 1RS arm have longer roots than lines with the 1RS^RW arm in both field and hydroponic experiments. In the 1RS^RW lines, differences in seminal root length were associated with a developmentally regulated arrest of the root apical meristem (RAM). Approximately 10 d after germination, the seminal roots of the 1RS^RW plants showed a gradual reduction in elongation rate, and stopped growing a week later. Seventeen days after germination, the roots of the 1RS^RW plants showed altered gradients of reactive oxygen species and emergence of lateral roots close to the RAM, suggesting changes in the root meristem. The 1RS^RW lines also showed reduced biomass (estimated by the normalized difference vegetation index) and grain yield relative to the 1RS lines, with larger differences under reduced or excessive irrigation than under normal irrigation. These results suggest that this genetic variation could be useful to modulate root architecture.