Developmental and morphological changes associated with flowering time shifts during divergent selection experiments in maize

International audience

English. An original plant material resulting from a Divergent Selection Experiment (DSE) for flowering time of maize was developped over the last 20 years. Within two maize inbred lines, Early- and Late-flowering populations, subsequently structured into families within populations were formed. Comparisons between Early and Late populations or between Early or Late families within each DSEs allow to study the effects of flowering time shifts in the same genetic background.A strong response to selection was observed over the 20 generations and results indicate that this response is due to a variety of changes affecting different aspects of the life cycle. To better understand these changes, we set up field experiments to describe plant growth and development for different families issued from the DSE (phyllochrone, growth rates, plant architecture, developmental transitions). We observed that differences between Early and Late progenitors concern timing of transitions, phyllochron, and the delay between the end of leaf emergence and blooming, while organs’ growth rates were much less variable. Comparisons of the different families suggest that phenotypic convergence for flowering time between Early or between Late progenitors is achieved through different developmental routes.This poster focuses on changes observed in leaf emergence rates (phyllochron) for early and late genotypes in different environments. It notably presents families * environment interactions which highlights the importance of environment in the control of developmental properties underlying flowering time.This poster focuses on the patterns of changes in plant morphology and architecture in relationship with developmental changes. Polymorphisms between Early and Late populations were found in all kinds of traits, morphological traits, developmental times (heterochrony) and growth rates. However, while changes in growth rates were small, we found marked differences in developmental timings associated with large morphological changes.