1) A synthetic variety is developed by inter-crossing multiple good inbred lines and mixing their F1 seeds. It partially exploits heterosis through open pollination over generations. 2) Synthetic varieties are developed to exploit heterosis and additive gene effects. They have wider adaptability than hybrids due to genetic diversity. 3) A synthetic variety initially consists of many heterozygotes, but some homozygosity is fixed over generations through self-pollination. Later generations consist of both heterozygotes and homozygotes.

1. Breeding Methods in cross pollinated
crops:
SYNTHETIC AND COMPOSITE VARIETY
Dr. NAVEENKUMAR K.L
Assistant Professor
Dept. of GPB
UAHS Shivamogga

2. What is synthetic variety?
A variety which is developed by inter-mating in all possible
combinations a number of inbred lines with good general
combining ability and mixing their seeds (seeds of F1s) in equal
quantity is referred to as synthetic variety.
VARIETY: in plant breeding, a strain released for commercial
cultivation by a variety release committee.
 It is relevant to cross pollinated species.
 The commercial utilization of synthetics varieties in maize was first
suggested by Hays and Garber (1922).

4. Why synthetic varieties are developed?
 The basic concept in the development of synthetic variety is
exploitation of heterosis.
 In the development of synthetics, heterosis is partially
exploited, because some degree of inbreeding takes place
due to open pollination in later generations.
What is genetic constitution of a synthetic variety?
 Initially, a synthetic variety consists of several heterozygotes.
 A synthetic variety is maintained by open pollination, some
degree of selfing occurs resulting in fixation of some
genes.
 As a result in later generations, a synthetic variety consists of
several heterozygotes and homozygotes.

5. Main features of synthetic variety
1. They are relevant to cross pollinated species.
2. They are maintained by open pollination.
3. They exploit more of additive variance.
4. In later generations, they consist of several heterozygotes and
homozygotes.
5. Synthetics have wider adaptability.
6. Synthetic varieties exploit more of additive gene action than
dominance gene action.
7. Generally, 5-8 good general combining inbred lines are used to
constitute a synthetic variety.
8. A synthetic variety can safely be grown for a period of 4-5
years without reduction in yield potential.

11. Synthetic 2 (Syn2) performance depends on
1. The number of parental lines (Syn0 population) constituting the synthetic.
2. On the differences in yielding ability of Syn1 and Syn0 generation.
 Syn1 is the first generation synthetic produced by mating in all possible
combinations the n parental lines.
 This relationship was first suggested by Sewall Wright (1922).
 Where, n is the number of parental lines entering the synthetic variety.
 The performance of Syn3 and the subsequent generations obtained by
random mating is expected to be comparable to that of Syn2, provided
contamination by foreign pollen and inbreeding are avoided.
 Available evidence shows that the above formula estimates the yield of
Syn2 populations quite reliably.
Syn2 = Syn1 – [(Syn1 – Syn0) / n]

12. Factors determining the performance of Synthetic varieties

15. Achievements
 Synthetic varieties have been developed in cross pollinated
crops like maize, pearl millet, sunflower, sugarbeet, alfaalfa,
lucerne and several other crops in USA.
 In India, synthetic varieties have been developed in pearl
millet at ICRISAT and in sugarbeet at Pantnagar university.
 In sugarbeet- Pant synthetic 3
 In cauliflower- synthetic 3

16. Composites
Concept originated in India.
Generally derived from varietal crosses in advanced generations.
Developed from OPV or heterozygous populations or germplasm (not
subjected to inbreeding/combining ability tests).
The composites often show higher heterosis in F1’s when widely
diversed populations are used.
GCA and additive gene affects play predominant role in exploitation of
these populations
Reconstitution is not possible
Composites may serve as a base population for developing inbred lines

17. Procedure
Screen diverse germplasms by evaluation at multilocations to identify the sources
having adaptability, desirable agronomic traits and resistance to major diseases
and pests.
I Year: Making all possible crosses among selected superior genotypes and
harvesting crossed seed separately.
II Year: Evaluation of F1 crosses in replicated trail using hybrid or open
pollinated variety as check.
III to IV Year: Evaluation of F2 , F3 and F4 generations replicated trail using
standard check, identification of crosses exhibiting little or no inbreeding
depression.
VI & VII Year: Mixing parental seed of superior crosses in equal quantity to
constitute composite variety , seed multiplication by open pollination in
isolation.
VIII Year: Release of new composite variety

18. Achievements
 Several composite varieties have been developed in maize in
India.
 The important varieties are Jawahar, Vijay, Kisan, Amber,
Sona, Vikram, Protina, Rattan, Shakti, Vikas, Tarun, Renuka,
Kanchan, Co 1 etc
 In Brassica compestris var toria an early maturing variety
known as composite 1 has been released.