ABSTRACT
Feral, or weedy, cereal rye (Poaceae: Triticeae, Secale cereale L.) is a widely distributed weed of agricultural and ruderal habitats. It persists in agricultural systems under strong selection pressure for crop mimicry as well as in non-agricultural systems under strong selection pressure for several non-cultivated traits. The diversity of weedy rye has led to much confusion about its origins as well as their potential impact. In the case of cereal rye, we cannot even be sure that all weedy rye is indeed feral (i.e., derived from a crop either directly or via hybridization) and not merely an ancestral form of cereal rye. Cereal rye is itself believed to have originated as a secondary crop from an ancestral weedy form of S. cereale in wheat and barley fields (26,47). Clearly, determining the origin of weedy rye and its relationship to cultivated rye is critical to understanding the evolutionary origins and adaptations of weedy rye populations. We will therefore first review taxonomic relationships within Secale. We will then provide an overview of domestication, followed by an introduction to dedomesticated and predomesticated forms of Secale cereale. Finally, we will present preliminary data from an investigation of the origin and divergence of feral rye in the western U.S. In this chapter, the term weedy rye will be used to refer to persistent annual cereal rye that could be ancestral or only distantly related to cultivated cereal rye, whereas feral rye will be used when we know that weedy plants are at least in part derived from cultivated cereal rye.
