Embryo culture is a technique used in plant propagation and plant breeding, particularly for species that may have difficulty germinating or growing under normal conditions. It involves isolating and growing plant embryos, which are the early developmental stages of plants, in a controlled environment, typically on a nutrient medium.

1. EMBRYO CULTURE

2. Embryo culture is a technique used in plant
propagation and plant breeding, particularly for
species that may have difficulty germinating or
growing under normal conditions.
It involves isolating and growing plant embryos,
which are the early developmental stages of
plants, in a controlled environment, typically on a
nutrient medium.

3. • EMBRYO CULTURE
EMBRYO CULTURE IS THE IN VITRO ISOLATION AND
CULTURE OF IMMATURE OR MATURE ZYGOTIC
EMBRYOS ON A NUTRIENT MEDIUM UNDER ASEPTIC
CONDITIONS FOR OBTAINING VIABLE PLANTS.
EMBRYOS ARE OFTEN USED AS EXPLANTS TO
GENERATE CALLUS CULTURES.
IMMATURE EMBRYOGENIC CALLUS, DERIVED FROM
SEED EMBRYO, IS THE MOST POPULAR METHOD OF
MONOCOT PLANT REGENERATION.

5. The first successful attempt to culture angiosperm
embryos was made by Hanning (1904).
He produced viable seedings by culturing the
isolated embryos of Raphanus and Cochleria on a
semi-solid medium. Currently, embryo culture is a
well established and widely popular method of tissue
culture.

6. Raphanus

7. Cochleria (scurvygrass)

8. Embryo culture involves the surface
sterilization, excision and transplantation of
embryos to a growth medium.
The most ideal energy source is sucrose.
Auxins and cytokinins are used for callus
formation, and gibberellins and abscisic acid
are used to promote embryogenesis.

9. Embryo culture is highly useful when
embryos fail to develop due to the
degeneration of embryonic tissues.
It is most usually applied for the
production of haploid plants,
propagation of orchids, and the
breeding of the plants with prolonged
seed dormancy.

10. There are two types of embryo culture,
namely culture of mature embryos and
that of immature embryos. The latter is
also called embryo rescue.

11. (a)Culture of mature embryos
This is the culture of mature seed embryos, derived from ripe
seeds. Generally, this method is adopted when the embryos
may not survive in vivo, or when they become dormant for
long periods. It is also adopted to overcome the inhibition on
seed germination. In many cases, seed dormancy is mainly due
to certain chemical inhibitors, or due to the mechanical
resistance of embryonic coverings, rather than due to the
dormancy of embryonic tissue. Such seed dormancy can be
bypassed by the excision of embryos from testa and culturing
them in suitable nutrient media. Embryos, excised from
developing seeds at or near the mature stage, can grow on a
simple inorganic medium, supplemented with an energy
source.

12. (b) Culture of immature embryos (embryo rescue)
Culture of immature embryos is also called embryo rescue, because its
main objective is to save or rescue the embryo from abortion. Embryo
rescue involves not only embryo culture, but also ovule culture and
ovary culture. During distant hybridization, the embryo often aborts at
an early stage of development. So, mature seeds may not be produced.
Incompatibility between embryo and endosperm may also cause the
improper development of the embryo. These problems can be solved
by immature embryo culture. In this case, the young hybrid embryo is
excised before abortion and then cultured on a suitable medium. This
cultured embryo can differentiate into shoot and root and thus can
directly develop to a young plantlet. When embryos are not easily
excisable, ovules are cultured.

13. Similarly, when ovules too are not excisable,
ovaries are cultured.
Thus, it becomes clear that culturing of mature
embryos promotes germination, but culturing of
immature embryos saves the embryo from
arrested development or abortion.
Embryo rescue is significant in hybridization,
breaking of seed dormancy, and the normal
growth of an embryo to a plantlet.

14. Embryo rescue renders interspecific crosses successful
when there is postfertilization disharmony between
embryo and endosperm. Such a post-fertilization
disharmony forms a barrier to seed-setting.
In this case, fertilization occurs, but the embryo
degenerates before attaining maturity. Embryo rescue
technique has been widely applied for the successful
production of interspecific hybrids in the genera
Trifolium and Lycopersicon, and also for the production
of intergeneric hybrids between Triticum and Aegilops,
between Triticum and Secale, etc.

15. Trifolium

16. Lycopersicon

17. Aegilops

18. Secale (RYE)

19. At the International Rice Research Institute,
Philippines, embryo rescue technique has
been successfully applied for the transfer of
the resistance against brown plant hopper
from a wild species of rice (Oryza officianalis)
to the cultivar species (O.sativa). The main
drawback of embryo rescue is that it is
applicable only to those distant crosses where
fertilization is normal, but there are post-
fertilization problems.

20. Significance of embryo culture
(i) Embryo culture can considerably reduce the
duration of the breeding cycle of economically
important plants.
(ii) (ii) Embryo culture renders rapid seed-viability test
easy.
(iii) Embryo culture can save the embryos produced by
distant hybridization from the danger of abortion.
(iv) Rare plants can be multiplied and propagated by
embryo culture.