Improvement of embryogenesis in cucumber (Cucumis Sativus L.) parthenogenesis by polyamine and cycocel treatments

This study evaluated the combined application of polyamines (putrescine, spermidine) and cycocel (CCC) to maternal plants in relation to the effect of pollen irradiation with gamma rays on seed formation, embryo formation and haploid production in three cucumber genotypes (Storm, Sahm, 547) using pollen irradiation at doses of 400 to 600 Gy. Maternal plants were treated with combination of putrescine (500 mg/L), spermidine (50 mg/L) and CCC (50 mg/L) from 12 days before to 12 days after pollination. Male flowers were irradiated with gamma rays (400, 500, 600 Gy) and pollination was performed. Embryos were rescued in vitro and regenerated plantlets were analyzed for ploidy level using flow cytometry and SSR marker to confirm haploid status. Haploid plants produced were treated with oryzalin for chromosome doubling. The combined treatment of polyamine and CCC significantly affected embryo induction and seed formation, with the Storm genotype producing the highest number of embryos and regenerated plants at a dose of 600 Gy. Embryogenesis and regeneration varied by genotype, with Storm and 547 showing the strongest responses; Sahm was the least responsive. Flow cytometry confirmed haploid/diploid status, and SSR validated homozygosity in doubled haploid (DH) lines. Higher gamma doses not only increased empty seeds but also embryo numbers, underscoring genotype-dependent radiation sensitivity. Controlled pollen irradiation combined with foliar polyamine/CCC pretreatment effectively induce haploid embryos and DH lines in cucumber, with strong genotype dependency and optimal effects at 600 Gy for certain genotypes. These findings support genotype-informed optimization of DH production and offer practical guidelines for accelerating cucumber breeding.