Synthetic variety: A variety which is developed by crossing in all possible combinations a number of lines that combine well with each other. The lines that make up synthetic varieties may be inbred lines, clones, open pollinated varieties or other populations tested for GCA or for combining ability with each other. The possibility of commercial utilization of synthetic varieties in maize was first suggested by Hayes and Garber in 1922. Synthetic varieties have been of great value in the breeding of those cross pollinated crops where pollination control is difficult, e. g. forage crop species, many clonal crops

1. Dr. Indrajay R. Delvadiya

2. Synthetic-Composite variety and
Hardy-weinberg law
Presented By :
Dr. Indrajay R. Delvadiya
Assistant Professor
Genetics & Plant Breeding
LPU
Dr. Indrajay R. Delvadiya

3. Synthetic varieties
Composite varieties
HARDY-WEINBERG LAW
Dr. Indrajay R. Delvadiya

4. Synthetic variety: A variety which is developed by crossing in all possible
combinations a number of lines that combine well with each other.
The lines that make up synthetic varieties may be inbred lines, clones, open
pollinated varieties or other populations tested for GCA or for combining
ability with each other.
The possibility of commercial utilization of synthetic varieties in maize was
first suggested by Hayes and Garber in 1922.
Synthetic varieties have been of great value in the breeding of those cross
pollinated crops where pollination control is difficult, e. g. forage crop species,
many clonal crops
e.g. cocoa.
Dr. Indrajay R. Delvadiya

5. Once synthesis, a synthetic variety is maintained by open
pollination in isolation.
Synthetic varieties are developed in maize, bajra, alfalfa, sugarbeet,
sunflower, cauliflower etc.
Heterosis is partially utilized by synthetic variety
Synthetic exploit more of additive gene action, while hybrids
exploit more of non additive gene action.
It has heterogeneous population
Synthetic varieties are highly adapted to environmental variation or
It provides stable yield in the fluctuating environments.
Dr. Indrajay R. Delvadiya

6. Operation in producing synthetic varieties:
The operations involved in the production of synthetic varieties are
illustrated as below.
-Evaluation of lines for GCA:
GCA of the lines to be used as the parents of synthetic varieties is
generally estimated by top cross or polycross test. The lines are
evaluated for GCA because synthetic varieties exploit that portion of
heterosis , which is produced by GCA.
-Production of synthetic varieties:
-Multiplication of synthetic varieties:
Dr. Indrajay R. Delvadiya

7. Dr. Indrajay R. Delvadiya

8. The yield of the synthetic varieties is always higher than
open pollinated varieties but lower than the yield of single
or double cross hybrids.
The seed of synthetic variety is much cheaper
The synthetic variety can be safely grown for 4-5 years
without reduction in yield.
The F1, F2, F3, F4 and F5 generations of a synthetic
variety are designated Syn1, Syn2, Syn3, Syn4 and Syn5
respectively.
Dr. Indrajay R. Delvadiya

9. Merits of synthetic varieties:
•Synthetic varieties offer a feasible means of utilizing heterosis in those
cross pollinated crop species where, the production of hybrid varieties
would not be commercially viable.
•The farmer can use the grain produced from synthetic variety as seed
to raise the next crop. There is no need to purchase fresh seed every
year.
•The seed of synthetic varieties is much cheaper than single or double
cross hybrids.
•Synthetic variety is more adaptable to environmental changes than
hybrids due to broad genetic base.
•Synthetic varieties are good reservoirs of genetic variability.
•The performance of synthetic varieties can be considerably improved
through population improvement.
Dr. Indrajay R. Delvadiya

10. Demerits of synthetic varieties:
The performance of synthetic varieties is usually lower than that of
the single or double cross hybrids, because of partial exploitation of
heterosis. They exploit GCA only.
The produce of synthetic varieties is generally less uniform and
less attractive than hybrid due to greater variability.
The performance of synthetic varieties is adversely affected by
lines with relatively poorer GCA.
Synthetic varieties can be produced and maintain only in cross-
pollinated crop species, while hybrid varieties can be produced both
in self and cross pollinated crops
Dr. Indrajay R. Delvadiya

11. Achievements of Synthetic Varieties:
Synthetic varieties have been developed in cross-
pollinated crops like maize, pearl millet, sunflower, Sugarbeet,
lucerne, etc. in U.S.A.
In India synthetic varieties have been evolved in pearl
millet at ICRISAT and in Sugarbeet at pantnagar.
Ex. Sugarbeet- pant synthetic – 3, Cauliflower- synthetic -3,
bajara- ICMS-7703.
Dr. Indrajay R. Delvadiya

12. Composite varieties
Dr. Indrajay R. Delvadiya

13. Composite varieties:
A composite variety is produced by mixing the seeds of several
phenotypically outstanding lines and encouraging open pollination to
produce crosses in all combinations among the mixed lines.
The lines are rarely tested for combining ability with each other.
The yield of composite varieties cannot be predicted in advance.
Like synthetics, composites are commercial varieties in cross
pollinated crops and are maintained by open pollination in isolation.
Dr. Indrajay R. Delvadiya

14. Steps In Development of Composite Variety
1. Selection of base or parental material
2. Intermating of selected genotype.
3. Evaluation of crosses.
4. Mixing of parental material of superior crosses in
equal quantity
Dr. Indrajay R. Delvadiya

15. Dr. Indrajay R. Delvadiya

16. Dr. Indrajay R. Delvadiya

17. Synthetic variety Composite variety
1) Number of inbred lines are less
(6-8)
1) Number of lines are more
(even up to 20)
2) That is produced by crossing in all
possible combination a number of lines
that combines well with each other.
2) That is produced by open pollination
among a number of outstanding stains.
3) Lines used in the construction of
syntheticvarieties are tested for
combining abilities.
3) Lines used in the construction of
composite varieties are not tested for
combining abilities.
4) Yield of synthetic variety can be
predictedin advance.
4) Yield of this variety cannot be
predicted inadvance
5) Exact reconstitution is possible. 5) Exact reconstitution is not possible.
Difference between synthetic varieties and composite variety
Dr. Indrajay R. Delvadiya

18. Hybrid Variety Synthetic Variety
1. Number of parents utilized are 2-4 1. Number of parents utilized are 4-10
2. Pollination is controlled 2. There is open pollination
3. Hybrid seeds are costly 3. Less costly
4. They exploit both GCA and SCA 4. Exploit GCA only
5. Seeds has to be replaced every year 5. Seeds has to be replaced after 4-5 years
6. It has narrow genetic base 6. It has wider genetic base
7. It is impossible to improve
performance of
7. It is possible to improve the
performance of the
Difference between hybrid and synthetic variety
Dr. Indrajay R. Delvadiya

19. Achievements: Composite varieties
1. In India, the first composite varieties were released in 1967: the six
maize composites were, Ambar, Jawahar, Kisan, Vikram, Sona and
Vijay.
2. Some of the recently released maize composites are: Co 1 (full
season, resistant to downy mildew), Renuka (very early), Kanchan
(very early).
3. Three opaque 2 composties, viz., Shakti, Ratan and Protina, have
been released in maize. They have twice the amount of lysine and
tryptophan as compared to the normal maize hybrids and composites.
4. A composite variety, Composite I, has been evolved in Brassica
campestris var. toria.
Dr. Indrajay R. Delvadiya

20. • Synthetic and composite varieties mostly relevant to ??????
• (a)Self pollinated
• (b) Both self and cross pollinated
• (c) Cross pollinated
• (d) None of these
• ANS ???...
Dr. Indrajay R. Delvadiya

21. • Base material used to produce synthetic varieties are ???
• (a)Open pollinated variety
• (b)clones
• (c)Inbred
• (d)All of these
• ANS ???...
Dr. Indrajay R. Delvadiya

22. • Yield prediction and reconstitution is possible
in case of Synthetic variety ????....
• (a) True
• (c) False
• ANS……???
Dr. Indrajay R. Delvadiya

23. CONCEPTS OF POPULATION GENETICS AND
HARDY-WEINBERG LAW
Dr. Indrajay R. Delvadiya

24. What is Hardy-Weinberg Law?
• This law was proposed by two scientists Hardy (1908) in England and Weinberg
(1909) in Germany independently.
• This Law states that," in a large random mating population gene and genotypic
frequencies remain constant from generation to generation in the absence of
selection, mutation, migration or random genetic drift.“
• In a diploid species, two alleles A and a and there are three genotypes, AA, Aa
and aa.
• Now, if we denotes the frequency of allele A as p and for allele a as q, and sum
of p and q is one i.e. p + q = 1.
Dr. Indrajay R. Delvadiya

25. In the same way frequency of genotype
AA = p 2 , Aa = 2pq and aa = q 2 ,
therefore p 2 (AA) + 2pq (Aa) + q 2 (aa) = 1
When gene and genotypic frequencies remain constant, population is in
equilibrium. This equilibrium is known as Hardy –Weinberg equilibrium.
Dr. Indrajay R. Delvadiya

26. Hardy-Weinberg Equilibrium Assumptions about the population

Large Population

No immigration or emigration

No mutation

Random mating

Random reproductive success (i.e., no selection)
Dr. Indrajay R. Delvadiya

27. Terminology :
• Random mating population: Cross-pollinated crops are highly heterozygous due to free
intermating of plants within a population. They are often referred as Random mating
population or Panmictic population or Mendelian Population.
• Mutation: A sudden heritable change in an individual and is generally due to a
structural change in a gene. Mutation may produce a new allele not present in the
population or may change the frequencies of existing alleles.
• Migration: The movement of individuals into a population from a different population.
Migration may introduced new alleles into the population or may change the frequencies
of existing alleles.
• Random genetic drift: The change in gene and genotype frequencies of a sample/
population entirely due to chance (small sample size, etc.).
• Selection: Differential reproduction rates of various genotypes is known as selection.
• Gene frequency: The proportion of an allele A or a, in the population. OR The
proportion of gametes carrying an allele A or a is known as gene frequency.
• Genotypic frequency or zygotic frequency: The relative proportion of a genotype AA,
Aa or aa in the population is known as genotypic or zygotic frequency.
Dr. Indrajay R. Delvadiya

28. A fundamental law of population genetics was developed by
(a) Hardy & Fisher (c) Hardy& Weinberg
(b) Weinberg & Flor (d) Hardy & Mather
ANS ????
Dr. Indrajay R. Delvadiya

29. A population in which each individual plant having equal chance to mating with
other individual of that population
(a) Random mating population (c) Mendelian population
(b) Panmictic population (d) All of these
Dr. Indrajay R. Delvadiya

30. Dr. Indrajay R. Delvadiya