Determination of the origin of the cold-adapted populations of barnyard grass (Echinochloa crus-galli) in eastern North America: a total-evidence approach using RAPD DNA and DNA sequences

This survey attempts to establish the origin of cold-adapted populations of barnyard grass (Echinochloa crus-galli (L.) Beauv.) in North America using molecular techniques, including random amplified polymorphic DNA (RAPD) and two types of sequences: chloroplast intron (trnL (UAA)) and rDNA nuclear spacer (ITS 1). There exists many possible scenarios to explain the origin of E. crus-galli in eastern Canada (Quebec), but we dwelled on two particular hypotheses, which are not mutually exclusive. The first hypothesis stipulates that the populations originated only from Europe, whereas the second implies that native subtropical and warm-temperate populations migrated from the south towards northern regions. To assess the likelihood of these hypotheses, the genetic distance matrices obtained from RAPD markers, nuclear, and chloroplastic sequences were combined and tested against the competing models. A principal coordinate analysis was used to discriminate among populations sampled from three different regions...