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What is the role of cytogenetics in plant improvement?
Cytogenetics is the science of chromosome number, shape, type and their inheritance,
recombination and expression. It is the science which deals with the evolution and
improvement of organisms.
During last few decades, plant cytogenetics has got a drastic improvement with the help
of molecular techniques. Development in plant cytogenetics can be divided into some
1. In first phase of development the scientists focused on the structural and
numerical variation of the chromosomes.
2. In the second phase of development in cytogenetics, scientists concentrated on
the DNA content and composition of unique as well as repeated forms of DNA
3. The third phase of cytogenetics brought the trend of marker assisted breeding,
marker associated traits and use of molecular markers in detecting linkages.
This technique led to the formation of physical maps of chromosomes of various
4. Later era led to the study of whole genomics of plants and gene sequencing,
chromatin remodeling and histone coding.
Cytogenetics has played a very important role in producing new and improved varieties
of plants in order to fulfill the food, fiber and shelter requirements of human beings. One
of the great examples is GM crops.
Genetically modified plants:
Genetically modified (GM) plants have altered DNA, using genetic engineering techniques. It is done to introduce a new character to the plants
which they do not have already. GM plants are still not very popular among the
people as there might be many health risks related to them. Review of some of
the GM plants is given below:
1. The most widelyaccepted and highly used GM crop is GM Soybean which contains resistant gene to herbicides glycophosate.
This resistant gene has been extracted from bacteria resistant to
herbicides. 77% percent people all over the world use this GM
soybean. 2. Bt. Cotton is the 2nd highest exploited crop, all over the world. It
has been grown by 49% of cotton growers in the world. Bt. Cotton
imposes resistance to pests by producing Cry toxin. This Cry toxin
producing gene has been obtained from a soil bacterium Bacillus
thuringiensis. 3. Bt. Maize is also an important and extensively accepted GM crop.
Bt. Maize has also the same CRY1-gene as in the Bt. Cotton. It
has also been made resistant to herbicides glycophosate by
inserting a resistance gene from bacteria. Some genes from South
African white corn have also been inserted in the GM maize in
order to obtain bright orange kernel with high degree of vitamin C
and carotene. 4. Experiments on falvr savr tomato production are on a high swing
now a day. Technology used to produce flavr savr tomato is the
insertion of antisense gene, responsible for production of an
enzyme polygalacturonase (PG). This antisense gene restricts the
production of PG enzyme which initiates ripening/softening in the
fruit after harvest. Flavr savr tomatoes have been taken off from
the markets of USA because it did not get commercial acceptance
but, they are still being grown in China on small scale. 5. Prototype GM rice contained three transgenes. Two of which came
from daffodil and one from a soil bacterium. Latest golden rice
contains genes from maize and a soil bacterium. Golden rice
shows enhanced content of bêta carotene, which is a source of
vitamin A. It is assumed that the golden rice would be marketed in
the year 2013.
No doubt the knowledge of cytogenetics has played a vital role in crop improvement and
we expect much more prospects from this field.
Nathan M. Springer. Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, Saint Paul, MN 55108, USA
Scott A. Jackson
Department of Agronomy, Purdue University, West Lafayette, IN 47906, USA
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