Microspore Embryogenesis Induced by Low Gamma Dose Irradiation in Apple

Flower buds and extracted anthers of two apple genotypes, ‘Golden Delicious’— a previously known non-androgenic genotype — and ‘Topred’— a known androgenic genotype —, were irradiated by gamma-rays at doses ranging from 5 to 20 Gy, after 0 to 5 weeks of cold pre-treatment (3 °C). When the extracted anthers were irradiated, both microspore embryogenesis and callogenesis were limited for the two genotypes. For ‘Golden Delicious’, androgenic embryogenesis was induced from the flower buds irradiated at 10 to 20 Gy and after 3 to 5 weeks of cold pre-treatment. For ‘Topred’, androgenic embryogenesis was slightly improved after flower bud irradiation at 5 to 10 Gy following cold pre-treatment from 0 to 3 weeks; it was limited after 5 weeks of cold pre-treatment.