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.In the greenhouse, flooding did not affect SFW or number of tillers, but decreased RFW. Drought drastically decreased all three parameters. Root and shoot growth of these genotypes in hydroponic culture were positively correlated to their root and shoot growth under both control and flooded conditions, but not under drought. Thus it appears that the expression of genotypic root growth potential may be influenced by the availability of soil moisture.Averaged over environments, the RFW in hydroponic culture was significantly correlated with SRLD (r = 0.93**). For individual genotypes, the correlation between SRLD or RFW in hydroponic culture and grain yield was not significant. As a group, however, the genotypes with larger RFW in hydroponics or higher SRLD produced higher grain yield than their small rooted counter parts. While further evidence is needed, our results indicate that selection for large-rooted seedlings in hydroponic culture may select genotypes capable of producing larger roots and perhaps higher yields in the field.U of I OnlyETDs are only available to UIUC Users without author permissio