Agriculture Reference
In-Depth Information
2010
). It has been estimated that about one-third of the world's potentially viable
land suffers from inadequate supply of water, and of the remainder, crop yields are
periodically decreasing due to drought and salinity (Kramer
1980
). Most of the
world's agriculturally important major cereal crops such as wheat, rice, maize and
barley growing areas, are affected routinely by drought. Therefore, it is important to
develop crops using suitable biotechnological methods which will be tolerable un-
der adverse environmental conditions and breeders are educated on new technology.
2.2.5 Doubled Haploid Technology (Androgenesis) for Crop Improvement
The ability to transform and regenerate plants represents the most powerful tool
and advancement in the field of plant biotechnology (Datta
2005
). Through andro-
genesis (anther and microspore culture), complete homozygous plants can be pro-
duced within a year as compared to the long durational inbreeding method, which
normally requires at least six inbreeding generations. The principle of androgenesis
is to arrest the development of the pollen grains (male gametophytes) and to force
them towards a somatic pathway (Datta
2005
). It provides the most commonly used
method for the production of doubled haploid plants that is eventually applied in
breeding and crop improvement. Most of these lines exhibit wide adaptability, high
resistance to drought, salinity and infertile soil, and luxuriant growth (Bikash and
Mandal
2001
). But even this widespread use of DH technology is impeded by the
lack of a technique, which can satisfy all of the expected criteria for a successful
system (Snape et al.
1986
), e.g., (i) easy, consistent production of large numbers of
DHs of all genotypes in the breeding program, (ii) DHs should be genetically nor-
mal and phenotypically stable, and (iii) recombinant DH populations should contain
an adequate sample of the genetic variation in the parents.
2.2.6 Genetic Engineering for Crop Improvement
Davey et al. (
2010
) mentioned that gene manipulation, combined with the ability to
induce cultured plant cells to express their totipotency leading to the regeneration of
fertile plants, provides a unique opportunity to extend the genetic pool available to
breeders for crop improvement. Cereal crops have been recalcitrant to recombinant
techniques mainly because of problems in establishing regenerable cell and tissue
cultures as well as due to efficient DNA delivery systems (Koprek 1996). There are
different ways of introducing DNA into plant cells such as protoplast transformation/
electroporation, microinjection, biolistics gun, and transfer from
Agrobacterium tu-
mefaciens
(Dale and Schantz
2004
). Potrykus (
1990
) reported that
Agrobacterium
method is not possible to be used for transformation of monocotyledonous tissues.
But after the successful achievement of cereal crops by Hiei et al. (
1994
), Ishida
et al. (
1996
), Cheng et al. (
1997
) his finding was questioned. The most distinct way
of getting foreign DNA into a plant cell involves the bacterium
Agrobacterium tu-
mefaciens
. Through particle bombardment, improvement of transgenic cereal crops
