Primary Root Elongation Rate and Abscisic Acid Levels of Maize in Response to Water Stress

Agricultural crops are exposed to greater water deficits as production regions receive less rainfall and producers move into more arid landscapes to meet demand. Maintenance of root elongation is vital for seedling establishment in these types of climates. Some maize (Zea mays L.) lines can maintain primary root elongation under severe water stress (SS) conditions. Twelve maize inbred lines were examined at the seedling stage before leaf expansion to assess the phenotypic diversity in primary root elongation rate and root elongation zone abscisic acid (ABA) content at three water potentials, -0.03 MPa, -0.3 MPa, and -1.6 MPa. A phylogenetic tree was constructed using 93 simple sequence repeat (SSR) markers to examine genetic and phenotypic relationships among the lines in relation to stress response. Statistical analysis revealed phenotypic diversity in both primary root elongation rate and ABA content. No correlations were detected between the amount of ABA present in the root tip and the rate of root elongation in any of the treatments. Histograms of primary root elongation response to the varying water deficits suggest multiple mechanisms may be responsible for the response to water stress observed in different maize lines. Different phenotypic responses toward water stress were observed for lines with small genetic distances, which will aid in identification of specific alleles for maintenance of primary root growth under water deficits.