3. Introduction
Requirement of fruits vegetables and cereals is
increasing proportionally.
Although conventional plant breeding techniques
considerably progressed in the development of
improved varieties.
They are unable to keep pace with the increasing
demand for vegetables fruits and cereals.
So there is a need to integrate genomics to speed up
the crop improvement programmes.
4. Conti.......
Genomic tools have revolutionized the entire crop
improvement programmes by providing:
New strains of plants,
Supply of planting material,
More efficient pesticides,
Improved fertilizers,
5. Conti….
The major areas of genomics which are adopted for
improvement of crops are:
Tissue Culture
Genetic Engineering
Molecular diagnostics
Molecular markers
Development of Beneficial microbes
6. Tissue Culture
It is one of the most widely used techniques for rapid
asexual in vitro propagation.
It is economical in time and space affords greater
output and provides disease free and elite propagules.
Can produce millions of uniformly flowering and
yielding plants.
Can produce virus free planting material using
meristem culture.
7. Conti…..
Plants regenerated by tissue culture exhibits
phenotypic variation atypical of the original
phenotype.
Such variation, termed somaclonal variation.
Heritable i.e. genetically stable and passed on to the
next generation.
These heritable variation are potentially useful to plant
breeders.
8. Genetic Engineering of Plants
Genetic Engineering involves three major steps:
i) Identification and isolation of suitable genes for
transfer
ii)Delivery system to insert desired gene into recipient
cells.
iii)Expression of new genetic information in recipient
cells.
Many transgenic plants have been developed.
9. Conti….
Genes for the following traits have been introduced to
the crop plants.
Herbicide tolerance
Engineering pathogen resistance
Stress resistance
Fruit Quality
Pest resistance
Male sterility and Fertility restoration
10. Herbicide tolerance
Herbicides tolerant plants allow farmers to spray crops
so as to kill only weeds but not their crops.
Tomato, tobacco, potato, soybean, cotton, corn oilseed
rape, petunia, etc.
Glyphosate is one of the most potent broad spectrum
environment friendly herbicide .
Glyphosate kills plants by blocking the action of an
enzyme EPSPS.
EPSPS is an essential enzyme in the biosynthesis of
tyrosine, phenylalanine and tryptophan.
11. Conti….
Transgenic plants resistant to Glyphosate have
been developed.
A number of detoxifying enzymes have been
identified in plants.
These include glutathione-s-transferase or GST in
maize and other plants which detoxifies the
herbicide.
Phosphinothricin acetyl transferase (PAT)
detoxifies the herbiside PPT (L-
phosphinothricine).
Herbicide tolerant plants reduce the use of
weeding labour, farmers cost and increase yield.
12. Engineering pathogen resistance
Viruses are the major pests of crop plants which cause
considerable yield losses.
Many strategies have been applied to control virus
infection.
Use of viral coat protein as a transgene for producing virus
resistant plants is successfully achieved in plant
genomics.
Coat protein gene from TMV has been transferred to
tobacco, making it nearly resistant against TMV.
13. Conti……
Nucelocapsid protein resistance gene has been
introduced in crops against tomato spotted wilt virus.
Use of satellite RNA makes many transgenic plants
resistant to Cucumber Mosaic Virus (CMV).
Transgenic resistant plants have also been developed
against
alfalfa mosaic virus,
potato virus X,
Rice tungro virus,
tobacco rattle virus,
Papaya ring spot virus.
14. Resistance Against Bacterial Diseases
Gene of Acetyl transferase is introduced in tobacco
making it resistant to Pseudomonas syringea, a causal
agent of wild fire disease.
15. Resistance Against Fungal Disease
Many of the antifungal compounds are synthesized by
plants which combat fungal infections have been
identified.
Chitinase gene from bean plants in tobacco and
Brassica napus showed enhanced resistance to
Rhizoctonia solani.
Chitinase gene obtained from Serratia marcescens is
introduced in tobacco making it resistant to Alternaria
longipes.
16. Stress Resistance
A number of genes responsible for providing resistance
against stresses have been identified.
Resistance against chilling was introduced into
tobacco by introducing gene for glycerol-1-phosphate
acyl-transferase enzyme from Arabidopsis.
Many plants respond to drought stress by synthesizing
polyols (Mannitol, Sorbitol and Sion).
Using a bacterial gene capable of synthesizing
mannitols it is possible to make plants resistant to
drought.
17. Fruit Quality
Tomatoes exhibiting delayed ripening have been
produced by using decreasing amount of enzymes
involved in ethylene production.
This increases the shelf life of tomatoes.
These tomatoes can stay on the plant long giving more
time for accumulation of sugars and acids for
improving flavour.
Starch content in potatoes has been increased by using
a bacterial ADP glucose pyrophosphorylase gene.
18. Pest Resistance
The insecticidal bt gene has been isolated from
Bacillus thuringiensis bacteria and transferred to
plants like cotton, tobacco, tomato, soybean, potato,
etc.
These genes produce insecticidal crystal proteins
which affect a range of insects.
These crystals upon ingestion by the insect larva are
solubilised in the highly alkaline midgut into
individual protoxins.
Insecticidal crystal protein produced during
vegetative growth of the cells are also found to be
highly effective against insect control.
19. Male sterility and Fertility Restoration
This is helpful in hybrid seed production.
Transgenic plants with male sterility and fertility
restoration genes have become available in Brassica
napus.
20. Molecular Diagnostics
Nucleic acid probes:
It is now possible to detect the plant diseases even before
onset of symptoms by using cDNA probes.
cDNA probes can be generated using standard
recombinant DNA technique.
21. Conti….
Monoclonal Antibodies (MCAB):
Hybridoma technology has provided methods for the
production of homologous and biochemically defined
immunological reagents.
These are of identical specificity and produced by a
single cell line directed against a unique epitope of the
immunizing antigen.
22. Molecular Markers
Molecular makers has made the job of breeder easier.
It has been possible to score the plants for different
traits or disease resistance at the seedling stage.
In plant breeding the use of following techniques is
numerous.
RFLP (Restriction Fragment Length polymorphism),
RAPD (Random Amplified Polymorphic DNA) ,
AFLP (Amplified Fragment Length Polymorphism)
