**4.4 Embryo rescue**

Embryo rescue is a dormancy alleviation method in which immature or mature zygotic embryos are isolated and cultured under aseptic conditions on an aseptic nutrient medium [87]. While the culture of immature embryos has as objective to prevent embryo abortion or sudden arrest of growth during ontogeny, one of the reasons the mature embryos are cultured is to eliminate seed germination inhibitors or to shorten the breeding cycle if dormancy is a problem [88]. The factors which cause dormancy are endogenous inhibitors and embryo immaturity. Breeding cycle can be shortened by removing the embryos from the influences of these factors which localized in the seed coat and endosperm, or both. The breeding cycle of papaya could be shortened via embryo culture from 6 to 9 months to approximately 3 months [89].
