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Quantitative selection for compact, high-yielding maize hybrids

SUMMARY Maize (Zea mays L.) hybrids with different productivity per unit approximate leaf projected area (ALPA) were compared in China, 1990–92. The results showed that the selection index (SI) values of all the hybrids tested decreased with an increase in population density. Nevertheless, the hybrids with high SI values at low plant densities also had relatively high SI values at high plant densities. Thus, high SI hybrids could be selected at any of these densities. Although no significant yield increase was obtained by using high SI hybrids at plant densities of 52500 plants/ha or lower; significant increases in yield were obtained for high SI hybrids at > 67 500 plants/ha. Leaf area was one of the parameters necessary for determining SI, and this could be predicted with a skewed bell-shaped function simply by measuring the length and breadth of the largest leaf and counting the total number of leaves per plant.