Bittercress (Brassicaceae) is one of the most prolific and costly weeds of the container nursery industry. Bittercress accessions from container nurseries throughout the major production zones in the United States were examined and compared with herbarium specimens. The identity of these weedy bittercress species were further explored using sequences of the nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) region and the nrDNA region for the COP1-interacting protein 7 (CIP7). Four species of bittercress were detected in the nursery industry of the United States, including New Zealand bittercress, hairy bittercress, flexuous bittercress, and little bittercress. The taxon referred to here as Cardamine flexuosa With. (flexuous bittercress) likely contains two genotypes previously reported as European C. flexuosa and Asian C. flexuosa. Phylogenetic relationships between the four species we examined, particularly in relationship to flexuous bittercress, were not fully resolved by the molecular evidence generated for this study. New Zealand bittercress is nonnative and does not appear in current keys to the species for the United States. Flexuous bittercress is also an alien species, which appears in some U.S. keys but not in all. To aid nurserymen and botanists in identification of these four closely related bittercress species, a key was developed and is accompanied by detailed descriptions and illustrations.

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The sweetpotato weevil (SPW), Cylas formicarius, is the most devastating insect pest of sweetpotato worldwide. In the U.S., the devastation by this pest costs the sweetpotato industry several million dollars in crop loss and lost income each year. Many growers in highly infested areas have simply abandoned growing sweetpotatoes. The overall project goals are to elucidate the routes used for the spread of the SPW, and to determine the existence of intra-specific variation in the SPW population in the US and selected overseas countries. These results will lead to more effective and targeted management of the SPW. Results will also make quarantine enforcement more efficient. We are examining the highly conserved and phenotypically neutral rDNA sequences of both the 18S and ITS1 regions of the SPW genome as a way to determine the population structures and origins of SPW in the US. Here, the molecular genetic aspects of the project are outlined, and preliminary results are presented.