Immature Embryo Rescue and Culture

Embryo culture techniques have many significant applications in plant breeding, as well as basic studies in physiology and biochemistry. Immature embryo rescue and culture is a particularly attractive technique for recovering plants from sexual crosses where the majority of embryos cannot survive in vivo or become dormant for long periods of time. Overcoming embryo inviability is the most common reason for the application of embryo rescue techniques. Recently, fruit breeding programs have greatly increased the interest in exploiting interploid hybridization to combine desirable genetic traits of complementary parents at the triploid level for the purpose of developing improved seedless fruits. However, the success of this approach has only been reported in limited number of species due to various crossing barriers and embryo abortion at very early stages. Thus, immature embryo rescue provides an alternative means to recover triploid hybrids, which usually fail to completely develop in vivo. This chapter will provide a brief discussion of the utilization of interploid crosses between a monoembryonic diploid female with an allotetraploid male in a citrus cultivar improvement program, featuring a clear and comprehensive illustration of successful protocols for immature embryo rescue and culture. The protocols will cover the complete process from embryo excision to recovered plant in the greenhouse and can easily be adapted to other plant commodities. Factors affecting the success and failure of immature embryo rescue to recover triploid progeny from interploid crosses will be discussed.