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Home » Biology Homework Help » Biotechnology » Embryo Rescue
Embryo Rescue
Embryo culture is being routinely used in some crop improvement programmes to obtain interspecific hybrids. It has some other specific uses as well, for example, propagation of orchids, overcoming dormancy etc. The various applications of embryo culture are briefly described below:

Distant crosses may fail to one or more of several reasons, e.g. inability of pollen to germinate, failure of pollen tubes to grow or, perhaps more commonly, degeneration of endosperm. When embryo fails to develop due to endosperm degeneration embryo culture is used to recover hybrid plants; this is called hybrid rescue. Embryo culture has been widely used for this purpose. Some recent examples are the recovery of hybrids from Hordeum vulgare × secale creale, Triticum aestivum × Agropyron repens, H. vulgare × Triticum species including T. aestivum etc.  Two examples of such an application of embryo culture will illustrate the point. In case of Triticale, rate combinations between Triticum and Secale develop viable seeds. But most of the tetraploid and hexaploid wheats carry two dominant genes Kr1 and Kr2, which prevent seed development in crosses with Secale. The majority of hybrid seeds are small, poorly developed and how poor germination. Further, seeds are obtained from only 5-10 percent of the florets pollinated. The recovery of hybrid seedlings is much greater (50-70 percent) when embryos from 10-14 day old caryopses are removed and cultured on a suitable medium.

Hybrid seeds from T. aestivum × H. vulgare are not obtained but hybrid seedlings have been obtained by embryo culture. Hybrid embryos from 9-12 day old caryopses were removed and placed on 14-18 day old barley endosperm cultured on a nutrient medium. As many as 10 hybrid embryos may be placed on a single endosperm. A high proportion of hybrid developed into seedlings when they were cultured.

In addition, some interspecific crosses, e.g. H. vulgare × H. bulbosum, T. aestivum × H. bulbosum, wheat × maize, yield embryos. Embryos culture is used to recover the haploid plants from such crosses which are then used in breeding programmes.

Propagation of orchids

Orchids are difficult to propagate since their seeds lack any stored food and the embryo is virtually naked. In many orchids, embryo development is incomplete at the time their seeds mature. Young or mature orchid embryos are removed from seeds and placed on suitable nutrient media. The embryos develop into seedlings either directly or through callus formation.

Shortening the breeding cycle

Seeds may take 10-20 days to mature after the embryo is sufficiently developed to permit successful culture in vitro. The embryos do not complete their development in vitro, but develop directly into seedlings. Thus the net generation may be grown one or two weeks earlier by embryo culture than from seeds. But this has not become a practical feasibility because of two reasons; first, embryo culture is an exacting and time consuming technique and, second, excellent greenhouse facilities are a prerequisite for such an application of the technique.

Overcoming dormancy


In some fruit trees, embryos require of after-ripening before germination. Iris seeds may take two to several years to germinate. This period of dormancy can be efficiently eliminated by embryo culture. Other examples are Prunus, Taxus etc.

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