Genetically modified (GM) papaya plant resistant to infection by Papaya Ring Spot Virus (PRSV) was successfully generated by cloning the coat protein (CP) gene of the PRSV. However, the food safety of GM foods remains controversial. This study assesses the food safety of two GM papayas, 16-0-1 and 18-2-4, and compares them with that of non-GM papaya, Tainung-2 (TN-2), using genetic and animal toxicity assays. Pulps of fresh papaya fruits were lyophilized and grounded before use. Three genotoxicity assays were performed: the Ames test of Salmonella typhimurium tester strains (TA98, TA100, TA102, TA1535 and TA1537); the chromosomal aberration of Chinese hamster ovary (CHO-K1) cells (in vitro); and micronucleus assays for mice (in vivo). Experimental results
demonstrated that both non-GM and GM papaya fruits had no genotoxicity. Acute oral toxicity and 28-day repeated feeding toxicity tests for these papayas were performed via the oral gavage method for rats. All GM papaya fruit had no acute toxicity at a maximal dose of 5 g/kg body weight. Furthermore, the results of the 28-day study at 1 g/kg body weight in rats revealed no adverse-related effect in the body weight, feed consumption, hematology, blood biochemical parameters, organ weights and pathology in both GMs and non-GM papaya groups. In conclusion, PRSV-resistant papaya fruit lines 16-0-1 and 18-2-4 are comparable to their parent non-GM (TN-2) counterparts and are equivalent in food safety.