Tropical soda apple samples were collected from 31 populations across the southeastern United States and from four populations in a portion of its native range in Brazil. The genetic relationships among these populations were examined by single primer amplification reactions (SPAR) and by sequencing a portion of the chloroplast genome. SPAR revealed no variation among the 132 individuals and only two chloroplast haplotypes were detected in the 50 individuals sequenced. The most common haplotype was present in all samples from the United States and most of the Brazilian samples, whereas the second haplotype was only found in one of the Brazilian populations. Within the limitations of these data, we conclude that Brazil is the best location to seek a potential biological control agent for tropical soda apple, and that, if identified, this agent should prove useful for populations throughout the United States.

Nomenclature: Tropical soda apple, Solanum viarum Dunal.

Additional index words: Chloroplast DNA, SPAR.

Abbreviations: cpDNA, chloroplast DNA; dNTPs, deoxynucleoside triphosphate; EDTA, ethylenediaminetetraacetic acid; PCR, polymerase chain reaction; RAPDs, randomly amplified polymorphic DNA; SPAR, single primer amplification reactions.