Shortening of breeding cycle: Occasionally, the breed¬ing work on horticultural plants such as deciduous fruit trees is delayed due to long dormancy periods of their seeds. By growing excised embryos on nutrient medium this period 'can be considerably cut down. For example, using this technique, Randolph and Cox (1943) could shorten the life-cycle of Iris from two to three years to less than a year. Rosa normally takes a whole year to come to flowering, but it has been possible to produce two generations by culturing its embryos.
Nickel (1951) demonstrated that in cultures, the excised embryos of crab apple (Malus sp.,) start germinating within 48 hours and within 4 weeks transplantable seedlings arc formed. By the end of 5 months the seedlings grow to a height of about a metre. On the other hand, the seeds, planted in soil take about nine months to germinate.
2. Rapid Seed - Viability Test: The possibility of break¬ing seed dormancy by embryo culture also allows the use of this technique as a rapid test for seed-viability. Barton (1961) has suggested that germination of excised embryos is reliable and capable of more exact interpretation than the commonly staining tests for seed-viability.
3. Propagation of Rare Plants: Some coconuts deve¬loped soft, solid fatty tissue in the place of liquid endosperm. Such nuts are called "Makapuno" which are very rare and served only at special banquets in Phillipines. Under normal conditions, the coconut seeds fails to germinate. But De Guzman (1969) has succeeded in raising plantlets from "makapuno" nuts by embryo culture method. These culture plants have been transplanted to field conditions and "makapuno" plants have been established. Recently De Guzman (1976) reported that 85% of the nuts borne by the plants were makapuno.
4. Obtaining Some Rare Hybrids: In plant breeding experiments, all the desirable crosses are not successful. A cross may fail due to various reasons. Very often in such crosses, the embryo dies at an early stage due to poor or abnormal development of the endosperm. In such cases, it is possible to raise complete hybrid plants through embryo culture. This method has been profitably used for many interspecific crosses. The caryopses formed in the crosses between Hordeum uulgare and H. bulbosum are frequently devoid of endosperm. As a result of this, the embryo dies prematurely. By excising hybrid embryos, 14-28 days after pollination, Davis (1960) was able to raise seedlings capable of transplantation to soil. For example, Iyer and Govila (1964) have raised hybrids from many interspecific crosses of Oryza which are otherwise impossible to obtain.
