Developmental changes associated with divergent selection for rind penetrometer resistance in the MoSCSSS maize synthetic

Rind penetrometer resistance (RPR) has been used to select indirectly for stalk lodging resistance in maize (Zea mays L). Breeding for stalk lodging resistance would be facilitated by a better understanding of developmental mechanisms affecting RPR. Vegetative development can be divided into juvenile-vegetative and adult-vegetative phases. Vegetative phase change occurs when juvenile-vegetative traits are replaced by adult-vegetative trails. The objective of this study was to determine indirect responses in the timing of vegetative phase change and other developmental traits in nine cycles of S0 phenotypic divergent selection for RPR in Missouri Second Cycle Stiff Stalk Synthetic (MoSCSSS). In the high direction of selection, vegetative phase change occurred at lower nodes while ear leaf number and total leaf number decreased. In the low direction of selection, vegetative phase change was delayed to higher nodes while ear leaf number and total leaf number increased. In both directions of selection, plant height was reduced and flowering occurred earlier. The timing of vegetative phase change may be a factor in determining the level of RPR and stalk lodging resistance. Alternatively, modifiers may exist in MoSCSSS that coordinately regulate vegetative phase change with traits, such as ear leaf number, that are directly affected by selection for RPR.