Root growth and drought resistance in potato hybrid progenies

In the field evaluation of all 25 potato hybrid progenies under three drought treatments, root characters such as root number, root dry weight and root-shoot ratio were found to be significantly different among progenies, but not among drought treatments. In the raised-bed evaluation of nine TPS-progenies under two drought treatments, similar results of the field test were obtained. For both tests, root characters were significantly correlated with shoot characters, notably with stem dry weight and total dry matter production. With regard to the influence of planting material types, no significant differences were found between the TPS seedling and the apical cutting derived plants of 12 progenies evaluated. Genotypic variation accounted largely for the differences in root, shoot growth and tuber yield. Female parent effects were found to be significant and often predominant in most characters studied. The magnitudes of male-female and genotype-drought interaction effects were quite small and often non-significant. The results indicate that root characteristics of potatoes are genetically inherited. Their heritability estimates were comparable to those of shoot characters and tuber yield. Raised-bed screening method provided comparable results to the field screening, indicating its validity for root and drought resistance studies. It is advantageous over the field screening because of the lesser space and time required for handling a number of screening populations. It can also ease the root characterization by minimizing the effect of soil heterogeneity which is often the main cause lowering the reliability of root estimates. For characterizing the root system, root dry weight, basal root number, and root-shoot ratio could be the more effective and reliable parameters than root density and rooting depth. Drought susceptibility index (DSI) did not appear as a good measure of drought resistance.