SELECTION FOR EARLY FLOWERING RESULTS IN SIMULTANEOUS SELECTION FOR REDUCED NUCLEAR-DNA CONTENT IN MAIZE

Several studies have indicated a possible link between genome size and earliness in maize. In this study, an original maize population, Sout h African photo-period insensitive maize composite II (C0) and several selected generations were analyzed for days to flowering, plant heigh t, ear height, and yield. The selection criterion was earliness. Over six cycles of selection a 14-day decrease in days to flowering was obt ained with no significant reduction in grain yield. In the initial pop ulation (C0) and the most advanced selection (C6) 101 plants were anal yzed for nuclear DNA content. A significant decrease in the mean nucle ar DNA content of the C6 population (102 AU) was observed with respect to the C0 population (105 AU). This reduction was the result of a dec rease in frequency of plants in the C6 population with large genome si zes. Therefore it was concluded that selection for earliness resulted in selection against plants with large genome sizes. Hence, the nucleo type of a maize plant can be modified by selection such as early flowe ring time.