15Two watermelon genotypes, one commercial watermelon variety (Ustun F1) and five 16 different doses of gamma rays coming from Co 60 were tested to develop useful haploidization 17 procedure in watermelon. For this purpose, male flowers collected a day before anthesis were 18 irradiated with 50, 150 , 200 , 275 and 300 Gy doses of gamma ray and female flowers were 19 pollinated with irradiated pollen the next day. Seeds extracted from fruits harvested 25 days later 20 were opened individually in a laminar flow hood. Embryos obtained via embryo rescue technique 21were placed in glass tubes containing CP medium with 30 g l -1 sucrose, 8 g l -1 agar, 0.08 mg l -1 22 B12, and 0.02 mg l -1 IAA. Sixty haploid embryos were obtained from 43 watermelon fruits in 23 this study. Genotype 1 was found to be the most successful genotype with 3.57 haploid embryos 24 per 100 seeds. Among tested irradiation doses, 275 Gy was better than other doses with 5.26 25 haploid embryos per 100 seeds. Considered together with irradiation dose and genotypes, the 26