Taskin, H., Yücel, N. K., Baktemur, G., Çömlekçioglu, S. and Büyükalaca, S. 2013. Effects of different genotypes and gamma ray doses on haploidization with irradiated pollen technique in watermelon (Citrullus lanatusL.). Can. J. Plant Sci. 93: 1165-1168. Two watermelon genotypes, one commercial watermelon variety (Ustun F1) and five different doses of gamma rays coming from Co⁶⁰ were tested to develop useful haploidization procedures in watermelon. For this purpose, male flowers collected a day before anthesis were irradiated with 50, 150, 200, 275 and 300 Gy doses of gamma rays, and female flowers were pollinated with irradiated pollen the next day. Seeds extracted from fruits harvested 25 d later were opened individually in a laminar flow hood. Embryos obtained via embryo rescue technique were placed in glass tubes containing CP medium with 30 g L^-1 sucrose, 8 g L^-1 agar, 0.08 mg L^-1 B12, and 0.02 mg L^-1 IAA. Sixty haploid embryos were obtained from 43 watermelon fruits in this study. Genotype 1 was found to be the most successful genotype with 3.57 haploid embryos per 100 seeds. Among tested irradiation doses, 275 Gy was better than other doses, with 5.26 haploid embryos per 100 seeds. Considered together with irradiation dose and genotypes, the maximum number of haploid embryos was obtained from Genotype 1 pollinated with 275 Gy irradiation dose, with 6.25 haploid embryos per 100 seeds.