VEGETATIVE PHASE-CHANGE IN SWEET CORN POPULATIONS - GENETICS AND RELATIONSHIP WITH AGRONOMIC TRAITS (VEGETATIVE PHASE-CHANGE IN OPEN-POLLINATED SWEET CORN)

Vegetative development in maize can be divided into juvenile and adult phases, each, with distinct anatomy and physiology. Transition from j uvenile to adult vegetative growth may have some adaptive value since adult leaves have increased photosynthetic rates, xeromorphism, and re sistance to certain insects and diseases. Variation in the timing of t his transition (i.e., the node(s) at which phase change occurs) may be associated with agronomic performance. Our objectives were to investi gate the genetics of the timing of vegetative phase change and the rel ationship between phase-specific developmental and agronomically impor tant traits in a diallel among open-pollinated sweet corn cultivars. S ignificant variability existed for most developmental traits evaluated in this study. Environmental effects were significant for some traits , whereas genotype x environment interaction (G x E) was significant o nly for number of leaves above the ear. General combining ability was significant and specific combining ability was not significant for mos t phase-specific developmental traits. Last leaf with juvenile wax and first leaf with adult wax were positively correlated. Ear leaf and to tal leaf number were not correlated with other phase-specific developm ental traits. Flowering time was negatively correlated with first leaf with adult wax but was not correlated with last leaf with juvenile wa x or last node with adventitious roots, indicating that some aspects o f vegetative phase change are not associated with the transition to re productive growth. Yield was not associated with any developmental tra it in this study. First leaf with adult wax and last leaf with juvenil e wax may be useful in selection indices, since they were not influenc ed by the environment, had no G x E interaction in this study, and hav e been associated with insect and disease resistance in previous studi es.