Prior research indicated that analysis of nuclear DNA content by flow cytometry could be used to distinguish smooth pigweed × tall waterhemp hybrids when the parent lines are known. Flow cytometry was performed on nuclei isolated from several Illinois populations of smooth pigweed and tall waterhemp. The smooth pigweed and tall waterhemp analyzed had nonoverlapping 2C nuclear DNA content values, with mean values of 1.04 and 1.34 pg, respectively. The consistent difference in DNA content observed between the two species indicates that DNA content analysis can be used to distinguish their hybrid progeny in natural populations.
Nomenclature: Smooth pigweed, Amaranthus hybridus L. AMACH; tall waterhemp, Amaranthus tuberculatus (Moq.) Sauer AMATU.