Evolution of Weedy Rice in a Domesticated Landscape

Red rice is a weedy relative of cultivated rice that infests crop fields and reduces harvests by up to 80%.  The weed is phenotypically diverse and occurs in rice fields worldwide, including regions with and without interfertile wild Oryza populations.  In the US, where no wild Oryzas occur, our previous work has indicated that the two major weed strains have evolved through independent de-domestications from Asian domesticated rice (indica and aus varieties).  This parallel evolution of weediness provides the opportunity to assess the relative roles of shared vs. distinct genetic mechanisms in the emergence of weed forms.  Inferences from analyses of genome-wide SNPs and candidate gene sequences are discussed.  A comparison of US weeds with those in Asia reveals an independent origin of weediness in Northeast Asia, as well as a major role for wild/weed introgression in regions of Southeast Asia where wild Oryza populations occur.