Renqiang Li, Muhammad Hameed, Koen Geuten
From slow, non-uniform germination to pre-harvest sprouting (PHS), both extremes of seed dormancy have posed challenges for plant breeders. Because this trait needs to be genetically tuned in relation to environmental cues, controlling the problem of pre-harvest sprouting can only be realized through a better understanding of the biological mechanisms of seed dormancy. Yet studying seed dormancy poses challenges, because of its complexity in the different modes of regulation (physical, chemical, developmental, physiological and genetic) in interaction with environmental cues (light, temperature, water and nutrients) and lack of natural variation in the commercial crop genetic resources. Building information from model systems can help guide our research efforts. While phylogenetically distant from temperate cereals, the available information for Arabidopsis is much more elaborate and can, to a certain extent, be translated. We therefore provide a comprehensive comparison of the mechanisms and pathways and indicate similarities, differences and knowledge gaps. While knowledge from Arabidopsis is highly valuable to guide seed dormancy studies in temperate cereals, effective knowledge translation that includes functional validation will often require the use of the more closely related "model system" Brachypodium. This model will also allow us to unravel derived or unique mechanisms in temperate cereals. As an indication of such derived mechanisms, we also discuss the genetic factors involved in seed dormancy control discovered in cereals, often through natural variation studies.