Soyabean-seed Yield Response in Row- and Hill-plots under a Recurrent Selection Programme

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