what is genetic purity ? need of genetic purity. maintenance of genetic purity. Seed classes, advantages of genetic purity. conclusion.

1. .
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2. CONTENT
Introduction
Need of Genetic purity
Factors responsible for Genetic purity Loss
Maintenance Of Genetic Purity during Seed
Production
Methods of Genetic Purity testing
Conclusion

3. What is Genetic Purity ?
Genotypic purity is simply defined as true to
type plants / seeds conforming to the
characteristics of the variety as described
by
the breeders.
Principle
Genetic purity or genuiness of the cultivar
is tested by means of heritable characters
(morphological, physiological or chemical)
of seeds, seedlings or plants.

4. Need of Genetic purity Testing
To increase crop production at national
level.
To increase farmers income and standard
of living.
To make IPR (plant breeders right and
plant variety protection) part strong.
For distinctiveness, uniformity and
stability (DUS) test.
Quality control of grains for processing.
Documentation of genetic resources.

5. Minimum standards for genetic purity for
different class of seeds
CLASS OF SEEDS
1. Breeder Seeds
2. Foundation seeds
3. Foundation seeds
4. Hybrids
PURITY %
100 %
99 %
98 %
95 %

6. Factors responsible for Genetic purity Loss
(kadam ., 1942)
Developmental Variation
Mechanical Mixtures
Mutations
Natural Crossing
Genetic drift
Selective influence of Diseases
Techniques of the Breeder
Breakdown of male sterility
Improper / defective seed certification System

7. 1. Developmental Variation:
 Seed crop is grown in difficult environmental
Conditions For several consecutive generations the
developmental variations may arise as differential
growth response.
To avoid or minimize such developmental variations
the variety should always be grown in adaptable
area

8. 2. Mechanical Mixture:
a.
Contaminati
on through
field – self
sown seed
or volunteer
plants
b. Seed
drill – if
same seed
drill is used
for sowing
2 or 3
varieties
d. Growing
2 different
varieties
adjacent to
each other.
e.
Threshing
floor
f. Combine
or
threshers
g. Bags or
seed bins
h. During
seed
processing
 It would be necessary to rogue the seed fields
at different stages of crop growth

9. 3. Mutations:
 It is not of much importance as the
occurrence of spontaneous
mutations is very low i.e. 10-7.
 If any visible mutations are
observed they should be removed
by rouging.

10. 4. Natural Crossing:
 It is an important source of contamination in sexually propagated
crops due to introgression of genes from unrelated
stocks/genotypes.
 The extent of contamination depends upon the amount of natural
cross-fertilization natural crossing is main source of contamination in
cross-fertilized or often cross-fertilized crops.
 The extent of genetic contamination depends on breeding system of
the species, isolation distance, varietal mass and pollinating agent.
 To overcome the problem of natural crossing isolation distance has
to be maintained.

11. 5. Genetic drift:
 When seed is multiplied in large areas only small
quantities of seed is taken and preserved for the next
years sowing.
 Because of such sub-sampling all the genotypes will
not be represented in the next generation and leads to
change in genetic composition. This is called as
genetic drift.

12. 6. Selective influence of Disease:
 In case of foliar diseases the size of the seed gets affected due
to poor supply of carbohydrates from infected photosynthetic
tissue.
 In case of seed and soil borne diseases like downy mildew and
ergot of Jowar, smut of bajra and bunt of wheat, it is
dangerous to use seeds for commercial purpose once the crop
gets infected.
 New crop varieties may often become susceptible to new races
of diseases and that leads to these varieties may become out
of seed
production programms.
 (Proper plant protection - major pests and diseases)

13. 7. Techniques of the Breeder
 Instability may occur in a variety due to genetic
irregularities if it is not properly assessed at the time of release.
 Premature release of a variety, which has been breed for particular
disease, leads to the production of resistant and susceptible plants
which may be an important cause of deterioration.
 When sonalika and kalyan sona wheat varieties were released in
India for commercial cultivation the genetic variability in both the
varieties was still in flowing stage and several secondary selections
were made by the breeders.

14. 7. Breakdown of male sterility:
Generally in hybrid seed production if there is any
breakdown of male sterility in may lead to a mixture of F1
hybrids
• 8. Improper Seed Certification
It is not a factor that deteriorates the crops varieties, but if
there is any lacuna in any of the above factors and if it
has not been checked it may lead to deterioration of crop
varieties.

15. Maintenance of Genetic Purity during seed
Production
1. Use of approved seed in seed multiplication
2. Inspection of seed fields prior to planting
3. Field inspection and approval of the Crop at critical stagesfor verification of genetic
purity, detection of mixtures,
weeds and seed borne diseases.
4. Sampling and sealing of cleaned lots
5. Growing of samples with authentic stocks or Grow-out test
Horne (1953) had suggested the following methods for
maintenance of genetic purity;

16. Maintenance of Genetic Purity during seed
Production
Steps suggested by Hartman and Kestar (1968) for
maintaining genetic purity
1. Providing
isolation to
prevent
cross
fertilization
or
mechanical
mixtures
2.
Rouging of
seed fields
prior to
planting
3.
Periodic
testing of
varieties
for genetic
purity
4.
Grow in
adapted
areas only
to avoid
genetic
shifts in
the variety
5.
Certificatio
n of seed
crops to
maintain
genetic
purity and
quality
6.
Adopting
generation
system

17. 1. Morphological /
Conventional grow
out test
2. Chemical test
3. Biochemical
markers (Proteins
and Isozymes)
4. Molecular
markers (DNA)
Methods to assess genetic purity

18. 1. Morphological test
In laboratory
 Examination features of seeds such as
length, width, thickness, shape, weight,
colour, seed coat colour etc. and comparing
them with those of authentic sample.
 Which are examined with naked eye / with
magnified hand lens / with the help of
scanning electron microscope

19. Traditional approach to purity testing Morphological
traits

20. Morphological test
In field
 The seed sample is sown in the controlled
condition with the authentic sample
 Genetic purity is determined on the basis of
observation made on the plant morphological
characters with reference to authentic
sample.
 Genetic purity is always expressed in
percentage
Grow out test

23. CONTENT

24. Limitations of morphological methods
 Environmental stress conditions often mask specific
morphological traits.
 Large amount of land required.
 Laborious
 Time consuming
 Unfavourable condition, i.e. disease and insect infestation may
limit GOT in field
 Morphological markers are becoming limited in relation to
rapid increase in number of varieties, hybrids and transgenics.

25. 2. Chemical tests
1. Phenol test
2. Modified phenol test
3. Potassium hydroxide –
4. Ferrous sulphate test
5. NaOH test

28. Advantages of chemical tests
 They are quick.
 They require virtually no technical expertise or training.
 Relatively inexpensive to conduct.
 No sophisticated equipments are required.
 The test permits detection of percentage admixture of
other type.
 Its results are usually distinct and easily interpretable.

29. 3. Biochemical methods
 Electrophoresis
Migration of a charged particle through a medium (agarose, polyacrylamide,
starch) under the influence of an electrical field. it is usually carried out in
aqueous solution
•A mixture of molecules of various sizes will migrate at different
velocities and will be separated.
The varieties are verified on the basis of banding
pattern.
1. By measuring Rm of bands
2. Total number of bands
3. Presence or absence of specific band
4. Intensity of band

32. 4. Molecular Marker
A genetic marker is a gene or DNA sequence with a known
location on a chromosome that can be used to identify individuals
or species.
Restriction Fragment Length
Polymorphism
RFLP
Random Amplified Polymorphic DNA RAPD
Amplified Fragment Length Polymorphism AFLP
Variable Number Tandem Repeat VNTR
Oligonucleotide Polymorphism OP
Single Nucleotide Polymorphism SNP
Allele Specific Associated Primers ASAP
Inverse Sequence-tagged Repeats ISTR
Inter-retrotransposon Amplified
Polymorphism
IRAP

33. General methodology for molecular markers
DNA extraction
PCR amplification
using nucleotide
primer
Initial
Denaturation
Repeated CyclesDenaturationAnnealing
Extension Final Extension
Electrophoretic
run and
identification of
PCR amplified
product.

36. Advantages and limitations of molecular techniques
 It has very large number of polymorphism
 development as compared to the bio-chemical markers.
 Residual heterozygosity can be detected.
 It is reliable to all crops.
 Very fast method.
 Sophisticated instruments required.
 Very costly.

37. Advantages of genetic purity
1. It is helpful in plant variety protection, registration,
certification and patents
2. to detect the even the minute genetic differences between
cultivars visa-a-versa for existence of novelty among essentially
derived varieties
3. Assurance of genetic purity for ensuring better agronomic
performance and predicted expectations
4. Prevention of misappropriation and willful admixture of seed/
cultivars at commercial or farmers level

38. Conclusion
• Combination of different methods make them accurate.
• Chemical test creates very less polymorphism and are
crop specific.
• Hybrid purity testing is possible before the sowing of
crop.
• Genetic purity analysis is the important Factor for
quality seed
• For farmer – No loss because of poor seeds + Higher
returns For