this presentation deals with the causes of varietal deterioration and the ways to overcome it. hope this will be useful for all the students.

1. Presented by:
Dr. Amita Sharma
Assistant Professor
Deptt. of Plant Breeding & Genetics
College of Agriculture, Balaghat
Madhya Pradesh

2. 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.

3. To increase crop production at national level.
To increase farmers income and standard of living.
To make IPR (plant breeder’s right and plant variety
protection) part strong.
For distinctiveness, uniformity and stability (DUS) test.
Quality control of grains for processing.
Documentation of genetic resources.

4. The genetic purity of a variety or trueness to its type
deteriorates due to several factors during the production
cycles.
Kadam (1942) listed the following important factors
responsible for deterioration of varieties.
1. Developmental variations
2. Mechanical mixtures
3. Mutations
4. Natural crossing
5. Minor genetic variations
6. Selected influence of pest and diseases
7. The technique of the plant breeder
8. Breakdown of male sterility

5. 1. Developmental Variations
When seed crops are grown under environments with
different photoperiods, or at different elevations for
several consecutive generation's developmental
variations may set in as differential growth responses. It
is therefore, preferred to grow the varieties of crops in
the areas of their developmental shifts.

6. 2. Mechanical Mixtures
 Most important reason for varietal deterioration.
 Two varieties growing next to each other’s field is
usually mixed during harvesting and threshing
operations.

7. The threshing equipment is often seeds of other varieties.
Similarly, the gunny bags, seed bins and elevators are
also often contaminated, adding to the mechanical
mixtures of varieties. Roguing the seed fields critically
and using utmost care during seed production and
preferably avoid such mechanical contamination.

8. 3. Mutations
 Mutations do not seriously deteriorate varieties. It is
often difficult to identify or detect minor mutations
occurring naturally.
 Mutants such as 'fatuoids' in oats or 'rabbit ear' in
peas may be removed by roguing from seed plots to
purify the seeds.

9. 4. Natural Crossing
 An important source of varietal deterioration in
sexually propagated crops.
 In self-fertilized crops, natural crossing is not a serious
source of contamination unless variety is male sterile and
is grown in close proximity with other varieties.

10. 5. Selected Influence of Pest and Diseases
 Selectively influence deterioration.
 The vegetatively propagated stock also can
deteriorate quickly if infected by virus, fungi or bacteria.
 Seed production under strict disease free conditions
is therefore essential.

11. 6. Minor Genetic variation
 It is not of much importance.
 Periodic testing of the varieties must be done from
breeder’s seed and nucleus seed in self pollinated crops.
 Minor genetic variation is a common feature in often
cross-pollinated species; therefore care should be taken
during maintenance of nucleus and breeder seed.

12. 7. The Techniques of the Plant Breeder
 Improper assessments in the release of new varieties.
 Premature release of varieties, still segregating for
resistance and susceptibility to diseases or other factors.
 Other heritable variations due to recombinations and
polyploidization may also take place in varieties during
seed production.

13. 8. 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 and selfers.

14. 9. Improper seed certification
It is not a factor that deteriorates the crops varieties, but
is 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.

16. Horne (1953) had suggested the following methods for
maintenance of genetic purity:
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
stages for 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.

17. Various steps suggested by Hartman and Kestar (1968)
for maintaining genetic purity are as follows:
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. Certification of seed crops to maintain genetic purity
and quality.
6. Adopting generation system.

18. Safe guards for maintenance of genetic purity:
The important safe guards for maintaining genetic purity
during seed production are;
1. Control of seed source
2. Preceding crop requirement
3. Isolation
4. Rouging of seed fields
5. Seed certification
6. Grow out test

19. 1. Control of Seed Source
The seed used should be of appropriate class from the
approved source for raising a seed crop.
a. Nucleus Seed: It is handful of seed maintained by
concerned breeder for further multiplication. The nucleus
seed will have all the characters that the breeder has
placed in it and it is of highest genetic purity. The quantity
of nucleus seed is in kilograms.

20. b. Breeder Seed: It is produced by the concerned breeder
or sponsoring institute or and which is used for
producing foundation seed. It is of 100% genetic purity.
c. Foundation Seed: It is produced from breeder seed and
maintained with specific genetic identity and purity. It is
produced on govt. farms or by private seed producers.

21. 2. Preceding Crop requirement :
This has been fixed to avoid contamination through
volunteer plants and also the soil borne diseases.
3. Isolation:
Isolation is required to avoid natural crossing with other
undesirable types, off types in the fields and mechanical
mixtures at the time of sowing, threshing, processing and
contamination due to seed borne diseases from nearby
fields.

22. 4. Rouging of Seed Fields:
The existence of off type plants is another source of
genetic contamination. Off type plants differing in their
characteristics from that of the seed crop are called as off
types. Removal of off types is referred to as roughing. The
main sources of off types are:
a. Segregation of plants for certain characters or
mutations,
b. Volunteer plants from previous crops or,
c. Accidentally planted seeds of other variety,
d. Diseased plants, Off type plants should be rouged out
from the seed plots before they shed pollen and
pollination occurs.

23. 5. Seed Certification:
Genetic purity in seed production maintained through a
system of seed certification. The main objective of seed
certification is to make available seeds of good quality to
farmers.

24. 6. Grow-out Test:
Varieties that are grown for seed production should be
periodically tested for genetic purity by conducting GOT
to make sure that they are being maintained in true form.
GOT test is compulsory for hybrids produced by manual
emasculation and pollination and for testing the purity of
parental lines used in hybrid seed production.

26. Methods to assess genetic purity
Morphological (In Laboratory or in field):
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.

27. Traditional approach to purity testing Morphological
traits

28.  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.

31. Limitations of morphological methods
 Environmental stress conditions often mask specific
morphological traits.
 Large amount of land required.
 Laborious.
 Time consuming.
 Unfavorable 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.

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

33. 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.

34. 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.

35. 4. Molecular Markers
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.

36. Advantages and Limitations of Molecular Techniques
 It has very large number of polymorphism development
as compared to the bio-chemical markers.
 It is reliable to all crops.
 Very fast method.
 Sophisticated instruments required.
 Very costly.

37. Advantages/Conclusion of Genetic Purity
1. It is helpful in plant variety protection, registration,
certification and patents.
2. To detect 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.