As a typical example of convergent evolution, seed shattering, or seed dispersal, has undergone repeated modifications throughout the evolutionary history of rice. This trait has been actively selected against in independently domesticated cultivated rice (Oryza sativa) populations but has been reacquired in independently evolved weedy rice (Oryza spp.) populations during de-domestication. My Ph.D. projects are dedicated to exploring the morphological and genetic bases of seed shattering in both cultivated and weedy rice from three distinct evolutionary lineages, including aus, indica and japonica. Through examining the morphology of the abscission zone (AZ), the specialized tissue responsible for seed detachment, across these cultivated and weedy rice populations, I found distinctive morphological adaptations employed by different cultivars to achieve their low shattering abilities. In contrast, high shattering weedy rice individuals exhibited a high degree of AZ convergence, despite their diverse origins. To ascertain whether the same or different loci contribute to the evolution of high shattering in independently evolved weedy rice populations, I conducted Quantitative Trait Loci (QTL) mapping in F2 progeny of a cross between a cultivar and its derived weed in the aus lineage. I identified five QTLs for seed shattering, some of which overlapped with regions showing signatures of positive selection. I found, however, that few detected QTLs overlapped with seed shattering QTLs identified in other weed x cultivar crosses, indicating a lack of genetic convergence in the evolution of shattering across weedy populations. Additionally, I performed comparative tissue-specific transcriptomic analyses to profile the gene expression in the AZ and its surrounding tissues in cultivated and weedy rice from distinct lineages across development. Different genes were found to explain the AZ morphological differences between cultivated and weedy rice in different lineages. The few overlapping genes between the lineages are likely involved in determining and maintaining AZ cell identity, potentially through modifying lignin and secondary cell wall deposition in these cells. My projects not only increase our understanding of seed shattering from both morphological and genetic perspectives, but also illustrate the extent of genetic and morphological convergence underlying the convergent evolution of seed shattering in distinct lineages.