Selection procedures in the development of maize inbred lines and the effects of plant densities on the relationships between inbred traits and hybrid yields

Abstract

<p>The purpose of this research was to use five selection procedures to develop inbred lines of maize (Zea mays L.):</p> <p>(1) to compare the selected lines for performance per se and in testcrosses at various plant densities, thereby evaluating the selection procedures; and</p> <p>(2) to determine the effects of plant densities on the relationships among plant, ear, and grain traits of the inbred lines and between these traits and hybrid yield performance.</p> <p>The source population was an Iowa Synthetic, BS1. Five groups of lines were obtained: Group 1, selected visually at a density of 59,000 plants/ha in rows spaced 102 cm; Group 2, selected visually and for one ear per plant at a density of 29,500 plants/ha in rows spaced 102 cm; Group 3, selected visually and for two ears per plant at a density of 29,500 plants/ha in rows spaced 102 cm; Group 4, selected visually at a density of 59,000 plants/ha in rows spaced 51 cm; Group 5, selected for testcross performance (double-cross tester) at 59,000 plants/ha in rows spaced 51 cm. Lines in groups 1 to 4 were selected in the S0 to S4 generations and lines in Group 5 in the S0 to S2 generations with some visual selection of the lines and plants when the testcrosses were produced. Nineteen lines in each of groups 1 to 4 and a control (BS1) were evaluated in testcrosses (double-cross tester) in eight environments, three plant densities per environment (Experiment I). Also, the lines in groups 1 to 4, 10 lines in Group 5, and the control were evaluated in testcrosses (double-cross tester) in two environments, 51-cm row width and 59,000 plants/ha (Experiment II).</p>