Root growth of wheat genotypes in hydroponics and soil in relation to water stress tolerance and grain yield

Root characteristics of wheat (Triticum aestivum L.) genotypes are believed to be important in tolerance to drought and flooding, yet neither the extent of differences in root size among modern soft red wheat genotypes, nor the degree of association between root size and drought or flooding tolerance is known. This study was conducted to see whether genotypes differ in root size, if root growth in hydroponic culture predicts root growth in soil, and whether root size is associated with grain yield and with tolerance to soil moisture stress. Differences in root fresh weight (RFW), shoot fresh weight (SFW), number of roots longer than 40 cm, longest root length, and total root length were observed for 40 winter wheat genotypes grown in hydroponic culture for 4 wk. All measured parameters were positively correlated with each other. Twelve genotypes with different root sizes selected from these 40 were grown in greenhouse and in field experiments under different soil moisture regimes. For six of these genotypes in three field environments, subsurface root length density (SRLD) was measured from soil cores in incremental depths between 13 and 120 cm.