Production of Common Sour Orange × Carrizo Citrange Hybrids Using Embryo Rescue

Citrus rootstock breeding is important in improving resistance to diseases, insect pests, and adverse environmental conditions. The majority of citrus species and cultivars have nuceller embryony, which causes some problems for breeding programs. This disadvantage can be eliminated by using embryo rescue. In this research, Common sour orange × Carrizo citrange were crossed in order to produce new rootstocks and immature embryos. The embryos were gathered from the crossed plants 80, 100, and 120 days after pollination. The immature embryos were transferred to 0, 0.5, and 1 mg/L GA ₃ containing medium to germinate them. In general, the later after pollination that the embryos were harvested, the higher the germination rate. Those harvested at 80 days averaged 32% over all treatments, while those harvested at 100 days averaged 77%, and those harvested at 120 days averaged 98% germination. Embryos on control media averaged 67% germination over all treatments, while those with 0.5 mg/L GA ₃ averaged 62%, and those with 1 mg/L GA ₃ in the media averaged 78% germination. The percentage of embryos developing trifoliate leaves for those harvested at 80 days averaged 51% over all treatments, while those harvested at 100 days averaged 24%, and those harvested at 120 days averaged 41%. Embryos on control media averaged 36% trifoliate leaf development over all treatments, while those with 0.5 mg/L GA ₃ averaged 35%, and those with 1 mg/L GA ₃ in the media averaged 44% germination.