Breeding for enhanced rooting depth androot biomass in deeper soil layers is a promisingstrategy to adapt wheat (Triticum aestivumL.) plantsto drought periods. We evaluated (1) the extent ofindirect selection of root traits during the last centuryof wheat breeding and (2) how it affected the varietyperformance under well-watered conditions comparedto gradually developing drought stress. Fourteen breadwheat genotypes covering 100 years of Swiss wheatbreeding were grown in 1.6 m tall columns in thegreenhouse under well-watered and drought condi-tions. Root parameters, such as rooting depth and rootbiomass and above ground parameters were deter-mined at flowering and maturity. Rooting depthshowed a negative trend in response to year of releaseunder well-watered conditions but not under earlywater stress. Modern varieties responded withenhanced root allocation to deeper soil layers. Conse-quently, rooting depth was positively correlated withplant height at well-watered conditions but not underearly water stress. Considerable genetic variation forrooting depth among modern varieties indicates thatthe trait is selectable without strong alteration of plantheight. We conclude that modern varieties adjustedrooting depth to water demand.
