Divergent Mass Selection for Leaf Chlorophyll Content Measured Using Chlorophyll Meter Readings in a Maize Composite Population
Leaf chlorophyll content is correlated with photosynthetic activity indicators and leaf nitrogen concentration. Three cycles of divergent mass selection for chlorophyll content were performed to estimate heritability, response to selection, and correlated changes in grain yield for these traits in a synthetic maize (Zea mays L.) population. Selection for high and low chlorophyll content was performed in the field using the SPAD chlorophyll meter, and response to selection was measured in field evaluations of the C-0, C-1, C-2, and C-3 populations. The divergent selection responses cycle-1 were 1.2 SPAD unit increase versus 0.2 decrease at anthesis and 0.9 increase versus 0.9 decrease at grain-filling period relative to the base average of 55.9 and 53.5, respectively. The C-3 high and low selections showed significant differences in chlorophyll content at anthesis and grain filling stages, but no significant selection indirect response was detected for grain yield. Thus, our data indicate that leaf chlorophyll content is heritable and that it can be manipulated through conventional breeding methodology. Additional cycles of chlorophyll content selection are needed to determine if chlorophyll content will be useful as an indirect selection criterion for yield improvement.