Application of Genetic, cytogenetic, and biotechnological techniques in the breeding of different field crops
Author: Dr. Prashant (Plant Biotechnology)
The
combination of genetic, cytogenetic, and biotechnological techniques has
significantly advanced the field of crop breeding, allowing scientists to
develop improved cultivars with targeted traits. These techniques are applied
in the plant breeding of various field crops:
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B. Cytogenetic Techniques: Cytogenetic techniques focus on
the chromosomal aspects of plant genetics, providing insights into chromosomal
structures, ploidy levels, chromosomal aberrations, etc.
C. Biotechnological Techniques: Biotechnological techniques
involve manipulating organisms' genetic material to achieve desired traits.
This includes genetic engineering, genome editing, and other new-age molecular
tools including MAS, Genomics, and other omics tools.
Applications of these three main techniques in crop
breeding:
The above techniques are elaborated on one by one: (See below)
A. Genetic
techniques
have revolutionized the field of plant breeding, enabling breeders to develop
crops with enhanced traits and improved agricultural sustainability. Here are
some applications of genetic techniques in the breeding of various field crops:
1.
Improved
Yield and Quality:
Genetic techniques allow breeders to select and manipulate genes associated
with increased yield, disease resistance, and better nutritional content. For
example, in rice and wheat, genes for high yield and nutritional value have
been identified and incorporated.
2.
Disease
Resistance:
Genetic engineering can introduce genes from naturally resistant plants into
susceptible crops to confer resistance against diseases. This has been used in
crops like potatoes to provide resistance against late blight.
3.
Pest
Resistance:
Genetic techniques have been employed to create crops that express insecticidal
proteins, reducing the need for external chemical pesticides. Breeding for
transgenic Bt cotton, for instance, produces a protein toxic to certain pests.
4.
Abiotic
Stress Tolerance:
Crop plants can be modified to withstand environmental stresses such as
drought, salinity, and extreme temperatures. Stress-tolerant varieties of maize
and rice have been developed using genetic techniques.
5.
Nutritional
Enhancement:
Biofortification involves enhancing the nutritional content of crops. Golden
rice, for example, has been engineered to produce higher levels of vitamin A to
address vitamin A deficiency in regions where rice is a staple food.
6.
Delayed
Ripening:
Genetic modification can be used to delay the ripening of fruits to extend
shelf life and reduce post-harvest losses. This has been applied in crops like
tomatoes and bananas.
7.
Herbicide
Tolerance:
Genetic techniques have been used to create crops resistant to specific
herbicides. This allows farmers to control weeds more effectively without
harming the crop.
8.
Polyploidy
Induction:
Polyploidy, the multiplication of the entire genome, can be induced using
genetic techniques. This has been employed to develop seedless varieties in
crops like grapes and watermelons.
9.
Hybrid
Development:
Genetic techniques are used to create hybrid plants with superior traits by
selectively combining genes from different parents, resulting in increased
yield, vigor, and uniformity.
10.
Conservation
of Genetic Diversity:
Genetic techniques are used in germplasm banks to conserve diverse genetic
material, ensuring a broad genetic base for future breeding efforts.
11.
Marker-Assisted
Selection (MAS):
Now a day’s merger of recent techniques like MAS (involves using molecular
markers linked to specific traits) to select plants in early generations is
used by conventional breeders. This speeds up the breeding process by allowing
breeders to select desirable plants without waiting for the trait to be
expressed.
B. Cytogenetic
techniques
play a crucial role in plant breeding by providing insights into the
chromosomal makeup, structural variations, and genetic relationships of
different crops. These techniques aid breeders in developing improved cultivars
with desired traits. Applications of cytogenetic techniques in the improvement
of various field crops are enlisted below:
1.
Chromosome
Counting and Ploidy Determination:
Cytogenetic methods like karyotyping help determine the number of chromosomes
in a plant species and identify different ploidy levels. This knowledge is
vital for hybridization and developing polyploid crops with enhanced traits.
2.
Creation
of Chromosome Maps:
Cytogenetic techniques, such as fluorescence in situ hybridization (FISH),
enable the construction of detailed chromosome maps. These maps aid in
understanding genome organization and assist in targeted gene introgression.
3.
Introgression
of Desired Traits:
Cytogenetic techniques facilitate the transfer of specific chromosomal segments
containing desired traits from wild relatives to cultivated crops through
methods like chromosome engineering or wide hybridization.
4.
Translocation
Breeding:
Chromosome translocations involve exchanging genetic material between
chromosomes. Cytogenetic techniques can be used to identify translocations that
confer resistance to pests, diseases, or environmental stresses.
5.
Detection
of Aneuploids:
Cytogenetic analysis helps identify plants with aneuploid conditions (abnormal
chromosome numbers) resulting from meiotic errors. Aneuploids can sometimes
exhibit novel traits valuable for breeding.
6.
Mapping
QTLs:
Quantitative trait loci (QTLs) associated with complex traits like yield,
quality, and disease resistance can be localized on chromosomes using molecular
cytogenetic techniques. This aids in marker-assisted selection.
7.
Genome
Comparisons and Evolutionary Studies:
Comparative cytogenetics enables the study of chromosomal rearrangements,
duplications, and deletions, providing insights into crop evolution and
relatedness.
8.
Detection
of Structural Aberrations:
Cytogenetic techniques can identify structural abnormalities such as
inversions, deletions, and duplications. These alterations can influence gene
expression and phenotype.
9.
Assessment
of Chromosomal Stability:
Cytogenetic analysis helps monitor chromosomal stability during tissue culture
and propagation, ensuring the production of true-to-type plants.
10.
Genetic
Mapping in Linkage Studies:
Cytogenetic tools contribute to genetic linkage maps, enabling the identification
of genes associated with traits of interest.
11.
Hybrid
Verification:
Cytogenetic methods, such as genomic in situ hybridization (GISH), aid in
confirming hybrid status by distinguishing between genomes of different
parental species.
12.
Genetic
Diversity and Conservation:
Cytogenetic techniques help assess genetic diversity within and between crop
species, assisting in germplasm conservation and breeding programs.
C. Biotechnological
techniques
have revolutionized the field of plant breeding, enabling scientists to
manipulate genetic information and develop crops with desired traits more
efficiently. Applications of biotechnological techniques in the breeding of
various field crops are enlisted below:
1.
Genetic
Modification (GM) or Genetic Engineering (GE): Biotechnology allows the
insertion of specific genes into plants to confer desired traits, such as
insect resistance, disease resistance, herbicide tolerance, and improved
nutritional content.
2.
Marker-Assisted
Selection (MAS):
MAS involves using molecular markers linked to specific traits to select plants
in early generations. This speeds up the breeding process by allowing breeders
to select desirable plants without waiting for the trait to be expressed.
3.
Genome
Editing:
Techniques like CRISPR-Cas9 enable precise modifications of specific genes,
resulting in plants with targeted improvements. Genome editing has been applied
to develop disease-resistant and drought-tolerant varieties.
4.
Transgenic
Crops:
Transgenic crops are engineered with genes from other organisms to express
desired traits. For instance, Bt cotton produces a protein toxic to certain
insect pests.
5.
Crop
Protection:
Biotechnological methods can create plants with enhanced resistance to pests
and diseases through the introduction of specific genes. This reduces the need
for chemical pesticides.
6.
Abiotic
Stress Tolerance:
Genetic modification can confer tolerance to abiotic stresses like drought,
salinity, and extreme temperatures, enhancing crop resilience in challenging
environments.
7.
Nutritional
Enhancement:
Biotechnology allows the development of crops with improved nutritional
profiles, addressing nutrient deficiencies in populations that rely on certain
staple foods.
8.
Virus Resistance: Transgenic crops can be
engineered to express virus-derived RNA fragments that trigger RNA interference, a natural defense
mechanism, providing resistance against viral infections.
9.
Reduced
Environmental Impact: Biotechnological approaches can
lead to reduced chemical usage (pesticides, herbicides) and promote more
sustainable agricultural practices.
10. Faster Breeding Process:
Biotechnology
accelerates breeding cycles by allowing breeders to introduce specific genes without the need for multiple
generations of crossing.
11. Hybrid
Development: Biotechnological tools contribute to the
development of hybrid plants with superior traits by selectively combining
genes from different parents, resulting in increased yield, vigor, and
uniformity.
12. Germplasm
Conservation: Biotechnological methods, such as cryopreservation
and tissue culture, aid in conserving plant genetic resources, preventing the
loss of valuable genetic diversity.
13. Validation
of Traits: Biotechnology helps confirm the presence of
specific traits early in the breeding process, ensuring that the desired
characteristics are present before further propagation.
These applications highlight the impact of
biotechnological techniques on crop breeding, fostering the development of
crops that are more resilient, nutritious, and sustainable, and contributing to
global food security and agricultural advancement.
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