SUMMARYTransition from juvenile to adult vegetative phase in maize is associated with pest and disease resistance. However, reports are not consistent on the significance and relative importance of additive or dominance genetic effects and variances. The purpose of the present research was to elucidate the genetic effects and variances and to identify molecular markers associated with phase transition. Three cycles of divergent selection were carried out in a maize synthetic accelerating and delaying phase transition. Three and four inbred lines were released from the third cycles of late phase transition (LPT) and early phase transition (EPT), respectively. Generation mean analyses were performed from two LPT×EPT crosses in order to calculate genetic effects and variances. Markers associated with vegetative phase transition were identified by contrasting simple sequence repeat (SSR) alleles between LPT and EPT inbreds and selection cycles, and by testing whether drift could explain the allelic changes observed in the respective third cycles of selection. Juvenile traits are mainly regulated by additive genetic effects and variances, whereas adult traits have a complex regulation involving dominance and epistatic effects. Based on error variances, EPT improves phenotypic stability. The SSRs phi028, phi112 and umc1725 were associated with selection for phase transition, suggesting that these genome regions are involved in the regulation of vegetative phase transition of maize, although none of the genes previously associated with phase transition has been located in those regions.
Response to Selection for the Timing of Vegetative Phase Transition in a Maize Population
