Euphytica 127: 335–344, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. 335 Obtention of haploid embryos and plants through irradiated pollen technique in squash (Cucurbita pepo L.) E.S. Kurtar 1 , N. Sarı 2 & K. Abak 2 1 Ondokuz Mayıs University, Professional High School of Bafra, 55410, Samsun, Turkey; 2 Çukurova University, Faculty of Agriculture, Department of Horticulture, 01330, Adana, Turkey Received 28 December 2000; accepted 12 February 2002 Key words: 60 Co, haploidy, irradiated pollen, ploidy determination, squash Summary The influence of gamma ray doses (25, 50, 75, 100, 200, 300 and 400 Gy) and genotypes (Eskenderany F 1 , Acceste F 1 , Sakız, Urfa Yerli) on the induction of haploid embryos obtained by irradiated pollen technique was studied in squash (Cucurbita pepo L.). Different shapes and stages of embryos were derived from seeds extracted from fruits harvested 4–5 weeks after pollination. As a result of the present study, haploid embryos and haploid plants were obtained, with haploid production strongly influenced by gamma ray doses, embryo stages and genotypes. Gamma ray doses of 25 and 50 Gy gave the highest parthenogenetical response. All of the point shape, globular shape, arrow tips and stick-shaped embryos developed into haploid plants. However, only 53.8% of torpedo and 23.1% of heart- shaped embryos gave haploid plants. In contrast, cotyledon-shaped and amorphous-shaped embryos produced only diploid plantlets. The number of embryos per 100 seeds was the highest in ‘Eskenderany F 1 ’ and ‘Sakız’ genotypes. After in vitro culture, a total of 93 haploid plantlets were obtained. Introduction Haploidization techniques facilitate the production of pure lines from heterozygous plants in a single gener- ation and represent significant advantages for breeders and geneticists. Haploid plants can also be obtain spontaneously, but the frequency of this event is very low (Pochard & Dumas de Vaulx, 1971). At the present, haploid plants are produced by anther- microspore culture and ovule-ovary culture, or by pollination with incomplete pollen (treated with chem- icals, irradiated etc.). Spontaneous haploidy occurs rarely in squash (Cu- curbita pepo L.) as in other species of the Cucur- bitaceae family (Savin et al., 1988). Attempts to produce haploids by in vitro androgenesis and gyno- genesis in squash were unsuccessful (Chambonnet and Dumas de Vaulx, 1985; Shail & Robinson, 1987). Re- cently, gynogenic haploid embryo induction and plant obtention has been successful through irradiated pol- len technique in melon (Sauton & Dumas de Vaulx, 1987; Sarı et al., 1992; Maestro-Tejada, 1992; Cuny, 1992; Abak et al., 1996), cucumber (Truong-Andre, 1988; Sauton, 1989; Niemirowicz-Szczytt & Dumas de Vaulx, 1989; Ça˘ glar and Abak, 1999) and water- melon (Gürsöz et al., 1991; Sarı et al., 1994). Pollen irradiation was proved to be effective for haploid in- duction in melon, but the embryo yield was found to be highly influenced by different factors such as gen- otype, environmental conditions and irradiation doses (Ficcadenti et al., 1995). The aim of this research was to investigate the possibility of inducing haploid embryos of Cucurbita pepo L. through irradiated pollen technique. Material and methods Plant material As plant material, two F 1 hybrids (Eskenderany F 1 and Acceste F 1 ) and two local open-pollinated gen- otypes (Sakız and Urfa Yerli) were used. The seeds were sown with 30-day intervals, starting from the