breeding Lec 28 Synthetics and composites.ppt

Synthetics and composites ppt

1. Lec 28. Synthetics and composites
- steps in development of
synthetics and composites –
achievements – merits and
demerits

2. In cross pollinated species, heterosis can also be exploited partially in the
form of synthetic and composite varieties, because some level of inbreeding
takes place due to open pollination
A variety which is developed by intermating in all possible combinations a
number of inbred lines with good general combining ability and mixing the
seed of F1 crosses in equal quantity is referred to as synthetic variety.
Use of synthetic varieties for commercial cultivation was first suggested by
Hayes and Garber in maize.
After release, synthetic varieties are maintained by open pollination.
Synthetic varieties

3. Applicable to cross pollinated crops.
Generally, 5-8 good general combining inbreds are used.
Genetic constitution - mixture of hetero and homozygotes and heterogeneous population.
Highly adaptable to environmental variations.
After five years, it would be desirable to reconstitute the synthetic variety.
Yield is higher than OPV but lower than hybrids
Designation - Syn1, Syn2, Syn3…
Features

4. 1) Isolation of inbreds
The exact reconstitution is possible when the parental lines are inbreds..
2) Evaluation of inbreds for GCA
Top cross method
3) Intermating of Good GC inbreds
Inbred lines selected for superior gca are crossed in all possible combinations.
n(n-1)/2
4) Mixing of F1 seeds
Seed of all possible F1 crosses is mixed together in equal quantity. The variety thus developed is called as Syn1.
The seed of such variety generally multiplied by open pollination in isolation for one or two generation (Syn1 and Syn2) and
then distributed to the farmers for commercial cultivation (Syn3)
Procedure for developing Synthetic variety

5. Year Breeding Activity
First Isolation of inbreds
SecondEvaluation of inbreds in replicated trials for GCA. Three
methods - top cross method, polycross and single crosses.
Third Intermating among the selected inbreds having good GCA.
The all possible single crosses would be n (n-1)/2.
Fourth
and
Fifth
Mixing the seeds of single cross seeds in equal quantity and
seed multiplication by open pollination for one or two
generations
Sixth Release as a new synthetic variety and seed distribution to
the farmers for commercial cultivation
Procedure for developing synthetic cultivar from
already available inbred lines

7. In cross pollinated crops, the mixture of genotypes from several sources that is
maintained in bulk from one generation to the next is referred to as composite variety.
Composite varieties
Features
Mixing the seed of various genotypes which are similar in maturity, height,
seed size and colour. The variety is maintained by open pollination.
Evaluation for GCA usually not done.
Genetic constitution - mixture of hetero and homozygotes and
heterogeneous population.
Highly adaptable to environmental variations.
Reconstitution is not possible.

8. 1) Selection of base material
Open pollinated varieties or heterozygous sources.
With similar maturity duration, height, seed size and seed colour.
2) Intermating selected genotypes
Crossed in all possible combinations. n(n-1)/2. each cross harvested separately.
3) Evaluation of crosses
Evaluated in replicated trials for yield performance in F1, F2, F3 and F4 using standard check.
Crosses exhibiting little or no inbreeding depression are identified and selected for development of composite cultivar
4) Mixing the parental seed of superior crosses
Parental seed of superior crosses is mixed in equal quantity.
Seed multiplication is carried out by open pollination in isolation.
Procedure for developing composite variety

9. Year Breeding Activity
First Selection of genotypes based on maturity duration, height,
seed size and seed colour
Second Intermating selected genotypes in all possible combinations n
(n-1)/2. The seed of each cross is harvested separately
Third to
Fifth
Evaluation of crosses in replicated trials for yield
performance in F
2, F
3, F
4 generations in replicated trials using
standard check, identification of crosses exhibiting no
inbreeding depression
Sixth and
Seventh
Mixing parental seeds of superior crosses in equal quantity
which constitutes composite variety
Eighth Release of new composite variety, distribution of seed to the
farmers for commercial cultivation
Procedure for developing composite variety

10. Achievements through synthetic/composite
varieties
Synthetic varieties - widely used in forage crops and in crops
where pollination control in difficult.
The maize breeding programme at CIMMYT, Mexico and the Pearl
millet breeding programme at ICRISAT, Hyderabad emphasized
development of synthetic varieties generally through population
improvement.
 Six maize composites were released first in India during 1967
and they were Amber, Jawahar, Kisan, Vikram, Sona and Vijay.

11. Recently released Maize composites
Bajaura Makka,
Pant Sankul Makka 3,
Chandramani,
 Pratap Kanchan 2,
 Pratap makka 4,
 Pratap Makka 5,
Pusa Composite 3 and
 Pusa Composite 4.
 Shakti,
Rattan,
Protina,
Shakti 1,
VL Baby Corn 1,
VL 78 and CoBC1.

12. Synthetics Composites
Parental components are generally
inbreds or clones
Parental components are OPV or
any other source
Evaluation for gca is always doneUsually not done
No of parental lines are limited to
4 - 6 inbreds
No such limit
Synthetic produced with inbreds
can be reconstituted
It is not possible
Yield performance can be
predicted
Cannot be predicted

13. Merits
Exploitation of heterosis where hybrid seed production is difficult
Synthetic variety is much cheaper than hybrids.
More adaptable to environmental changes than hybrids
No need to purchase fresh seed every year.
Demerits
Less uniform and less attractive than hybrids.
Yield is generally poor than hybrids.
Utilized in cross pollinated species only.

14. Thank YOU