Cereal inflorescence: features of morphology, development and genetic regulation of morphogenesis

Abstract

Cereals (Poaceae Barnh.) are the largest family of monocotyledonous flowering plants growing on all continents and constituting a significant part of Earth's many ecological communities. The Poaceae includes many important crops, such as rice, maize, wheat, barley, and rye. The qualitative and quantitative characteristics of cereal inflorescences are directly related to yield and are determined by the features of inflorescence development. This review considers modern concepts of the morphology, development and genetic mechanisms regulating the cereal inflorescence development. A common feature of cereal inflorescences is a spikelet, a reduced branch that bears florets with a similar structure and common scheme of development in all cereals. The length and the structure of the main axis, the presence and type of lateral branches cause a great variety of cereal inflorescences. Complex cereal inflorescences are formed from meristems of several types. The transition from the activity of one meristem to another is a multi-step process. The genes involved in the control of the cereal inflorescence development have been identified using mutants (mainly maize and rice) with altered inflorescence and floret morphology; most of these genes regulate the initiation and fate of meristems. The presence of some genetic mechanisms in cereals confirms the models previously discovered in dicotyledonous plants; on the other hand, there are cereal-specific developmental processes that are controlled by new modules of genetic regulation, in particular, associated with the formation of a branched inflorescence. An important aspect is the presence of quantitative variability of traits under the control of developmental genes, which is a prerequisite for the use of weak alleles contributing to the variability of plant growth and yield in breeding programs (for example, genes of the CLAVATA signaling pathway).