Hybrid Embryo Rescue: A Non-Conventional Breeding Strategy in Horticultural Crops

Production of interspecific and intergeneric hybrids is useful for transfer of desirable genes from wild species into cultivated species. In many instances, progeny from wide crosses is difficult to produce owing to several barriers. Post-zygotic barriers such as endosperm abortion and, at later stages, embryo degeneration are of common occurrence, leading to low fertility; but these have been overcome through the use of embryo rescue and several hybrids have been developed. This approach is especially useful in horticultural crops, more so in fruit crops. In our laboratory, we have developed protocols for hybrid embryo rescue in several top-of-the-line fruit crops that suffer from an inability to cross naturally (e.g., distant crosses, use of seedless parent/s) or instances where initial fruit drop is very high. Thus, interspecific, intergeneric and intervarietal hybrids have been generated in mango, banana, seedless grape, papaya and seedless citrus using embryo rescue. Culture of embryos has also been demonstrated in rose, capsicum, hot pepper, onion and tomato. Among the very important strategies under non-GM biotechnologies figure techniques of hybrid embryo rescue, and related applications like ovule/ovary/placental cultures through sequential embryo culture. Embryo culture applied to practical problems is a tissue culture technique that has proven to be of greatest value to breeders.