Eighteen cycles of recurrent mass selection for early flowering in two maize synthetics

Abstract

The genetic basis of commercial maize (Zea mays L.) is quite narrow. The incorporation of exotic germplasm, i.e. all germplasm that does not have immediate usefulness without selection for adaptation, is a way of enhancing the genetic basis of the material that a breeder can use. The populations of maize ‘Purdue Synthetic A o2’ (Purdue A) and ‘Purdue Synthetic B o2’ (Purdue B) were subjected to 18 cycles of recurrent mas selection for early flowering in Northwestern Spain. To evaluate the efficiency of selection, the original populations, the cycles of selection 6, 12, and 18, and five hybrid checks were evaluated in four environments in Spain. Both populations responded positively to selection for earlier female flowering with linear regression being highly significant. The change in the number of days from planting to silking was similar in both populations (1.01 days to silking/cycle of selection). Plant height, kernel moisture at harvest, and yield decreased significantly in both populations. Selection for early silking was efficient and resulted on similar decreases of kernel moisture in both populations, but yield and biomass decreased strongly. Therefore, although we must pay careful attention to agronomical important traits, these early o2 populations can be incorporated to a breeding program under short season conditions.