Synthetic and composite variety

SYNTHETIC AND
COMPOSITE VARIETY
PRESENTED BY: Pawan Nagar
Reg. no.: 04-2690-2015
M.Sc.(Fruit Science)

SYNTHETIC VARIETIES
 The possibilities of commercial utilization of synthetic varieties in maize was
first suggested by Hayas and Garber in 1919.
 Synthetic varieties have been of great value in the breeding for those cross –
pollinated crop, where pollination control is difficult. E .g Alfalfa, cloves,
forage crop species etc.
 Even in maize improvement synthetic varieties are becoming increasingly important
,and in India there had been a considerable emphasis on synthetic development.
Synthetic varieties

Defination:A Variety which is produced by crossing in all combination
number of inbred lines that combine well with each other. Once synthesized, a
synthetic is maintained by open-pollination in isolation is referred as synthetic
variety.
 A synthetic varieties can developed from inbreds, clones, and open pollinated
varieties.
 The end products of recurrent selection, which are already tested for GCA are
generally, used to constitute synthetic varieties.
 Generally 5-8 good general combining inbreds are used to constitute a
synthetic variety.
 Synthetic variety consists of several heterozygous initially. Since subsequently
the variety is maintained by open pollination, some degree of selfing occurs
resulting in fixation of some genes.
 A result in later generation synthetic variety consists of several heterozygotes.
Thus a synthetic variety has a heterogeneous population.

Step in development in synthetic varieties:
 Development of synthetic variety consists of three major steps. i.e.
1) Evaluation of lines for GCA.
2) Production of synthetic variety,
3) Multiplication of synthetic variety.
1) Evaluation of Lines for GCA:
 The lines that make up a synthetic variety may be inbred lines, clones, open
pollinated variety of short term inbred lines.
 Inbred lines are evaluated for general combining ability because synthetic variety
exploit that portion of heterosis which is produced by GCA.

 There are three different methods of evaluating, which is produced by GCA. There
are three cross, Polycross and single cross . In top cross, the inbreds are crossed
with a common tester and the progeny are evaluated in replicated trials for general
combining ability of yield and yield contributing characters.
 In Polycross, selected inbreds are allowed to intermated by open pollination in
isolation and in single cross all possible single crosses are made among selected
inbreds.
 These crosses are evaluated for GCA of yield in replicated that using local variety
as a check
 Thus, inbred lines with good GCA are identified and finally selected for
development of synthetic variety.

2) Production of Synthetic Variety:
 A synthetic variety may be produced in one of the following two
ways:
a) Equal amount of seed from the parental lines (syno) are mixed and planted in
isolation. Open- pollination is allowed and produce crosses in all combinations.
The seed from this population is harvested in bulk; the population raised from this
seed is the Syn1 generation.
b) All possible crosses among the selected lines are made in isolation Equal amount of
seed from each cross is composite to produce the synthetic variety. The population
derived from this composited seed is known as synthetic one generation.

c)Multiplication of Synthetic Variety:
 After a synthetic variety has synthesized. It is multiplied in isolation for one or
more generation, before its distribution for cultivation This is done to produce
commercial quantities and is a common practical in most of the crops. E. g
Grasses, Clover, Maize.
 In heterozygosity as a consequences of random mating. However, there would
net be a noticeable decline in the subsequent generations produced by open –
pollination (syn3, syn2, syn5, etc). Since the zygotic equilibrium for any gene is
reached after one generation of random mating.
 The synthetic varieties are maintained by open pollinated, seed, and may be
further improved through population improvement, particularly recurrent
selection.

Method 1: Equal seed from all
the parental lines is mixed and
planted in isolation. Open-
pollinated seed harvested as the
synthetic variety.(syn1)
Method 2: The parental lines
are planted in a crossing block
,and all possible intercrosses
are made among them .Equal
seed from all the crosses is
mixed to produce the synthetic
varieties.(syn2)

 Heterogeneous
 Synthetic variety can be developed by using clones, inbreds or OPV i.e. open pollinated
variety.

 Cross pollination is must .
 Maintained by open pollination.
 Unlike composite variety, exact reconstitution of synthetic variety is possible .
 More adaptive to varying growing conditions as compared to hybrids.

 Less uniform as compared to hybrids .
 Less attractive as compared to hybrids .
 Show some amount of heterosis as compared to OPV .
 Have better disease resistance
Features of Synthetic Variety

 Constituent genotypes can be two to ten. This number means a lot to achieve
maximum heterosis. Heterosis increases with increase in number of contributing
genotypes, but only up to 6 genotypes. Decreases when number increases to 10.
 Farmer can use his own saved seed for 4 years as there is no reduction in yield up
to that period, after that seed should be replaced .
 Low yielder than single cross hybrids or double cross hybrids but yield higher than
inbreds.
 Production is less costly as compared to hybrid varieties.

Merits of Synthetic Varieties:
1) Synthetic varieties offer a feasible means of utilizing heterosis in crop species where
pollination control is difficult.
2) Farmers can use the grain produced from a synthetic varieties as see to raise the next
crop.
3) In variable environments synthetic are likely to do better than hybrid variety.
4) The cost of seed in synthetic variety is relatively lower than hybrid varieties.
5) Seed production in case of synthetic variety required less skill operation than hybrid.
6) The performance of synthetic varieties can be considerably improved through
population improvement without reducing variability, whichis not possible with
hybrids
Merits, Demerits and Achievement of Synthetic Varieties:

1) The performance of synthetic variety is usually lower than best single or double
cross hybrid.
2) Synthetic variety can be produced and maintained only in cross-pollinated crop.
3) The performance of synthetic variety is adversely affected to relatively poorer
GCA.
.
Demerits of Synthetic Varieties:

Factors determining the performance of synthetic varieties:
Decline in
Heterozygocity
Decline in syn2
performance
Enhancing the
performance of
syn2
Increase the number
of parental line
Increasing the
performance
of syn1
Improving the
performance
of parental line

 Synthetic varieties have been developed in cross- pollinated crops like maize,
pearl millet, sunflower, Sugarbeet, alfalfa, lucerne, etc.
 In India synthetic varieties have been evolved in pearl millet at ICRISAT and in
Sugarbeet at pantnagar.
 Ex. Sugarbeet- plant synthetic – 3, Cauliflower- synthetic -3, bajara- ICMS-
7703.
Achievements of Synthetic Varieties:

COMPOSITE VARIETY:
 In cross pollinated crops, the mixture of genotype from several sources is
maintained bulk from one generation to the next is referred as composite variety.
Or
 Composite variety is a variety derived from advance generation of random mated
out standing lines (Germplasm inbreds, varieties, hybrids, advance generation
lines).
 Mixing the seeds of several phenotypically outstanding lines produces a
composite variety and encouraging open pollination to produce crosses in all
combinations among,the mixed lines.
 The lines used to produce a composite variety are rarely tested for combining
ability with each other like synthetic composite are commercial varieties and are
maintained by open – pollination in isolation.

 The line used a produce a composite variety are rarely tested for combining ability
with each other.
 Mixing the seeds of various genotypes, which are similar in maturity height,
seed size, colour, etc. develops composite varieties.
 The variety is maintained by open pollination. Farmers can use their own seed
for 3 to 4 years.
 The yields of composite verities cannot be predicted in advance ,which is
contrast to synthetic; this is because of yield of all f1 among the component
lines are not available .Like synthetic, composite are commercial varieties are
maintained by open pollination in isolation . Another type of population , called
germplasm complexes are produced by mixing seeds from several lines or
populations of diverse genetic origin.

 There is no restriction to the number of lines included in the development of
composite , but the line possessing desirable characteristics should be selected like
earliness, insect resistance, drought and frost resistance can be included in the
development.
 The seeds of desired selected lines mixed together and random mating is allowed
for 4-5 generations.
 Such uniform population is tested in replicated trials, across environment along
with standards checks and high yielding stable type can be released as composite
variety.
 The combining ability of lines used in composite are not tested, whereas in synthetic
each of the component is tested for its combining ability.
Procedure for Development Composite Variety:

 Heterogeneous
 Relevant to cross pollinated species only Can be developed from open pollinated
variety any other heterozygous variety .
 Farmer can use his own saved seed for 3 to 4 years, after that seed should be replaced .
 There can be two or more constituent genotypes .
Features of Composite Variety

 In India six composite varieties of maize like Amber, Jawahar, Kisan
Vikram, sona and Vijay have been released in 1967.
 Subsequently number of composite has been released in Bajara and
other crops.
 Some of the released composite of maize are Co-1 , NLD , Renuka and
Kanchan, Diara-3 etc, while in Bajara released composite are WCC-75,
RCBIC-9, ICTP-8203.
Achievement of Composite Varieties:Achievement of Composite Varieties:

SYNTHEIC VARIETIES COMPOSITE VARIETIES
Crossing in all combination of number of lines
that combine well with each other.
Mixing the seeds of several phenotypically
outstanding lines it and encouraging open
pollination to produce crosses in all
combination among the lines.
4-10 numbers of parents are involved
It is tested for GCA. Not tested for GCA.
Cost of seed is less than hybrid.
It shows less heterosis than hybrid. It shows more heterosis than synthetic
Reconstituted is done. Reconstituted is never done.
Maintenance of variety easy. Maintenance of variety is difficult but easy .
Prediction of performance possible. Prediction of performance is not possible.
Many parents are involved.
Cost of less than composite variety.

Synthetic and composite variety

Synthetic and composite variety

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Synthetic and composite variety