This document discusses methods of breeding in cross-pollinated crops. It describes mass selection, progeny selection (ear-to-row method), modified ear-to-row method, and recurrent selection. It also discusses hybrid varieties, synthetic varieties, and the operations involved in producing hybrids and synthetics. The key methods discussed are mass selection, ear-to-row selection, and recurrent selection.

2. Deva Ram
M.Sc Ag Seed science and
technology
Department of Genetics and Plant Breeding
SHIATS Allahabad UP. India

3. Contents
•Introduction
•Characters of cross pollinated crops
•Methods of breeding in cross pollinated crops
•Mass selection
•Progeny selection (or) ear-to-row method
•Modified ear-to-row method
•Recurrent selection
•Hybrid varieties
•Synthetic varieties
•Breeding methods common for both self and cross pollinated
crops
•Conclusion
•References

5. 1. Each genotype has equal chances of mating with all other
genotypes.
2. Individuals are heterozygous in nature.
3. Higher degree of inbreeding depression.
4. Wide adaptability and more flexibility to environmental
changes due to heterozygosity and heterogenity.
5. Cross pollination permits new gene combinations from
different sources.
6. Individuals have deleterious recessive gene which are
concealed by masking effect of dominant genes.

6. 1) Population improvement
1) Without progeny testing
1) Mass selection
2) With progeny testing
1) Progeny selection
2) Recurrent selection
2) Hybrid varieties
3) Synthetic varieties
Methods of breeding in cross pollinated crops

8. Mass selection is often described as the
oldest method of breeding.
Mass selection is an example of selection from
a biologically variable population.
Selection is based on plant phenotype.

9. Selection cycle may be
repeated one or more
times
Original population
FIRST YEAR
(FIRST SELECTION
CYCLE)
SECOND YEAR
(SECOND SELECTION
CYCLE)
i) Several plants selected on the basis of
phenotype
ii) Open-pollinated seed from the
selected plants harvested and bulked
i) Bulked seed from selected plants grown
ii) Mass selection may be repeated i.e., items
(i) and (ii) of the first year repeated
Yield trials
MASS SELECTION

10. Rapid and Simple breeding method.
Selection cycle is very short.
Have high heritability.
Effective in improving yield of cross
pollinated crops.

11. Phenotypic performance is greatly influenced
by environmental factors.
No control on the pollination.
Inbreeding depression.

12. Progeny selection
The simplest form of progeny selection is ear-to-row
method
Developed by Hopkins (1908)
This method was extensively used in Maize

13. ORIGINAL
POPULATION
MAY BE REPEATED
ONE OR MORE TIMES
YIELD TRIALS
FIRST
YEAR
SECOND
YEAR
THIRD
YEAR
i) Plants selected on the basis of
phenotype
ii) Open-pollinated seed from each
plant harvested separately
i) Small progeny rows grown from
the selected plants
ii) Superior progenies identified and
selected
iii) Plants allowed to open-pollinate;
seed is harvested separately
EAR-TO-ROW METHOD
Same as in second year
First
selection
cycle
Second
selection
cycle
Third
selection
cycle

14. It should be seen that ear-to-row method is
relatively simple and the selection cycle is of one
year only
However it suffers from the defect that plants in
the superior progenies are pollinated by those in
both the superior and inferior progenies ; this
reduces the effectiveness of selection

15. MAY BE REPEATED
ONE OR MORE TIMES
YIELD TRIALS
FIRST
YEAR
SECOND
YEAR
THIRD
YEAR
FOURTH
YEAR
i) Plants selected on the basis of phenotype
ii) Open-pollinated seed from each plant
harvested separately
i) Small progeny rows grown from the selected
plants
ii) Superior progenies identified
iii) Remaining seeds from the plants (selected in
first year) producing superior progenies
bulked to raise the next generation
Plants producing
superior
progenies
MODIFICATION OF EAR-TO-ROW METHOD
As in second year
First
selection
cycle
i) The bulk seed [yr 2, item(iii)] planted
ii) Plants allowed to open-pollinate
iii) Plants with superior phenotype selected
and seed harvested separetely
Second
selection
cycle

16. Merits of progeny selection
1.It is based on progeny test and not on the phenotypes
of individual plants hence it is far more accurate
reflection of the genotype than phenotype
2.Inbreeding may be avoided if care is taken to select a
sufficiently large number of plant progenies
3.Selection scheme is relatively simple and easy

17. Demerits of progeny selection
1.There is no control on pollination and plants are
allowed to open-pollinate. Thus the selection is
based on the maternal parent only
2.The selection time is two years. Thus the time
required for selection is as much as in the case of
mass selection

19. “Reselection of generation after generation with inter
breeding of selected plants to provide for genetic
recombination.
The procedure of Recurrent selection was described by
Jenkins in 1940.
The term Recurrent selection was given by Hull in 1945.

20. Simple recurrent selection.
Recurrent selection for general combining ability.
Recurrent selection for specific combining ability.
Reciprocal recurrent selection.

21. Selection is based on Phenotypic characters of plants.
Tester is not used in this scheme.
It does not measure the combining ability.
This method is useful only for those characters which
have high heritability.

22. 1st
YEAR
2nd
YEAR
3rd
YEAR
4 th
YEAR
MAY BE REPEATED AS IN 1st
CYCLE
Individual plant progenies are
planted.
All possible intercrosses are made
and seeds are composited.
Original
Selection
cycle
STEPS IN BREEDING A VARIETY BY SIMPLE RECURRENT SELECTION
Superior phenotypes are selected.
Selected plants self-pollinated
Seeds are harvested separately
Individual plant progenies are planted.
All possible intercrosses are made and
seeds are composited.
Composited intercross seeds are
planted .
selfing is done. 1st
Recurrent
selection
cycle

23. In this method selection is based on heterozygous tester cross
performance.
Improves general combining ability of population for a
character.
This method is used for genetic improvement of quantitative
characters.
Improves those characters governed by additive gene action.

24. 6th
Year
MAY BE REPEATED AS IN 1st
CYCLE
Original
Selection
cycle
SELF
POLLINATED
SEEDS
SELF
POLLINATED
SEEDS
TESTER
INTER CROSS BLOCK
INTER CROSS BLOCK
TESTER
REPLICATE
D YEILD
TRAIL
REPLICATE
D YEILD
TRAIL
1st
Recurrent
selection
cycle
1st
Year
2nd
Year
3rd
Year
4th
Year
5th
Year

25. In this method selection is based on Homozygous tester
cross performance.
Improves specific combining ability of population for a
character.
This method is used for genetic improvement of polygenic
characters.

26. 1st
Year
2nd
Year
3rd
Year
4th
Year
5th
Year
6th
Year
MAY BE REPEATED AS IN 1st
CYCLE
Original
Selection
cycle
1st
Recurrent
selection
cycle
SELF
POLLINATED
SEEDS
SELF
POLLINATED
SEEDS
TESTER
REPLICATED
YEILD TRAIL
TESTER
REPLICATED
YEILD TRAIL
INTER CROSS BLOCK
INTER CROSS BLOCK

27. In this method two heterozygous testers are used for crossing.
This scheme was proposed by Comstock,et al. in 1949.
Improves both GCA and SCA of population for a character.
This method is used for genetic improvement of polygenic
characters.
This method is also known as recurrent reciprocal half
sib selection.

28. 1st
Year
2nd
Year
3rd
Year
TEST
CROSS
TEST
CROSS
SEPARATE FIELD TRAILS
SELFEDSEEDS
SELFEDSEEDS
Original
Selection
cycle
COMPOSITE SEESDS OF INTERCROSS ARE RAISED
AND FIRST RECURRENT CYCLE IS REPEATED

29. Recurrent selection is efficient breeding method for increasing
the frequency of superior genes in a population.
It helps in maintaining high genetic variability in a population
due to repeated intermating of heterozygous population.
The selection is made on the basis of test cross performance
and only selected plants are allowed for inter mating.

30. This method involves lot of selection, crossing and selfing
work.
This method permits selfing which leads to loss of genetic
variability.
This method is not used directly for the development of new
varieties.

31. HYBRID VARIETIES
Hybrid varieties are the first
generations (F1) from crosses between
two purelines, inbreds, open pollinated
varieties, clones or other populations
that are genetically dissimilar
Hybrid varieties were first
commercially exploited in maize

32. Inbred:
A nearly homozygous line obtained
through continuous inbreeding of a
cross-pollinated species with
selection accompanying inbreeding
Top cross:
Cross between an inbred line and an
open-pollinated variety
Test cross:
Cross between F1 and homozygous
recessive parent
Single Cross:
A x B
Double cross:
(A x B) x (C x D)
Three way cross:
(A x B) x C
Varietal Cross:
A cross between
two varieties
Terminology related to production of
hybrid varieties

33. 1) Development of inbreds
2) Evaluation of inbreds
3) Production of hybrid seed
Operations in the production of
hybrid varieties

34. Development of inbred lines
Pedigree method is generally practiced in the development
of inbreds
First year:
•A number of plants with desirable phenotypes are
selected from source population and self-pollinated
•The selected plants should be vigorous and free from
diseases
•They may be selected on the basis of their GCA estimates
Second year:
•About 30-40 plants are space planted from the selfed
seed from each of the selected plants

35. Third to sixth years:
•Process of second year is repeated
•As the number of generations of self-pollination
increases, individual plant progenies would become
more and more homozygous
Seventh year:
•At this stage, individual plant progenies would be
almost homozygous
•Selfing may be discontinued and inbreds may be
maintained by sib-pollination

36. Evaluation of inbreds
If all the inbreds developed from an open-
pollinated variety were mated at random, the average
yield of all the single crosses would be the same as that
of the open-pollinated variety
Evaluation of inbreds may be divided into four steps
i)Phenotypic evaluation
ii)Topcross test
iii)Single cross evaluation
iv)Prediction of double cross performance

37. Phenotypic evaluation
•It is based on the phenotypic performance of the inbreds
•Highly effective for characters with high heritability
•Effective in improving the yielding ability of hybrids as the
yield of inbreds shows a small but positive correlation with the
performance of their hybrids
•Thus inbreds with poor performance can be safely rejected
Topcross test
•Reliable measure of the average performance of all single
crosses involving the inbred
•Genotypes remaining after the phenotypic evaluation are
crossed to a tester with a wide genetic base
•Performance of the top cross progeny is evaluated in replicated
yield trials
•About 50% of the inbreds are eliminated

38. Single cross evaluation:
•Inbreds remaining after top cross test are crossed in a diallel
manner to produce all possible single crosses
•In diallel system each inbred is crossed with every other inbred
•The performance of single crosses is evaluated in a replicated
yield trial
•Outstanding single crosses are identified and may be released as
hybrid varieties
Prediction of Double Cross Performance:
The predicted performance of any double cross is the average
performance of the four non-parental single crosses involving the
four parental inbreds

39. Production of hybrid seed
Requirements for hybrid seed production
1.Easy emasculation of the pollen parent
2.Effective pollen dispersal from the male parent.
Emasculation
Either hand emasculation or male sterility are used for emasculation
Male sterility is economical for commercial production
Pollination
Artificial pollination is applied for better seed set

41. Merits
•Exploit both GCA and SCA components of heterosis thus
utilizing heterosis to a greater extent
•Produce from hybrid varieties is more uniform as
compared to that of open-pollinated, synthetic or
composite varieties
•Genetic composition of hybrids don’t change over time
as they are maintained in the form of parental inbreds
•Can be produced both in self and cross pollinated species

42. Demerits
•Farmers have to use new hybrid seed every year
•Hybrid production requires considerable technical skill
which makes it tedious and costly
•Exploitation of full potential of hybrid varieties requires
an adequate and timely supply of inputs like irrigation,
fertilizers, weed control, etc. many farmers are unable to
ensure timely application of these inputs
•In most cross-pollinated species , the requirements of
isolation are rigid and difficult to fulfill except on large
farms

43. SYNTHETIC VARIETIES
•A variety produced by crossing in all combinations a
number of lines that combine well with each other is
known as a synthetic variety
•Once synthesized, a synthetic is maintained by open-
pollination in isolation
•The lines that make up a synthetic variety may be
inbred lines, clones, open-pollinated varieties, short
term inbred lines or other populations tested for GCA
or for combining ability with each other

44. 1. Evaluation of lines for GCA
2. Production of synthetic variety
3. Multiplication of synthetic variety
Operations in producing a synthetic
variety

45. Evaluation of lines for GCA
•GCA of the lines to be used as parents of synthetic
varieties is generally estimated by top cross or poly
cross test
•Poly cross refers to the progeny of a line produced
by pollination with a random sample of pollen from
a number of selected lines
•The lines are evaluated for GCA because synthetic
varieties exploit that portion of heterosis, which is
produced by GCA

46. Production of a synthetic variety
Method-1
•Equal amounts of seeds from the parental lines are
mixed and planted in isolation
•Open-pollination is allowed and is expected to
produce crosses in all possible combinations
•Seed is harvested in bulk; the population raised
from this seed is the syn1 generation
Method-2
•All possible crosses among the selected lines are
made in isolation
•Equal amounts of seed from all the crosses is
composited to produce the syn1 generation
Available experimental evidence suggests that both
the above methods produce comparable results

47. •After a synthetic variety has been synthesised, it is generally
multiplied in isolation for one or more generations before its
distribution for cultivation
•The open-pollinated progeny from the syn1 generation is termed as
syn2 , that from syn2 as syn3 , etc.
•The performance of syn2 is expected to be lower than that of syn1
due to the production of new genotypes and a decrease in the level of
heterozygosity as a consequence of random mating
•The synthetic varieties are usually maintained by open-pollination
seed and may be further improved through population improvement
schemes particularly through recurrent selection
Multiplication of synthetic variety

48. Inbreds, synthetics, open-
pollinated populations
X
Tester (open-pollinated
variety)
METHOD-I
Composited seed of all lines
METHOD-II
Crossing block
Equal seed from all
crosses composited
Seed multiplication
Open-pollinated
seed harvested
Step-1
Evaluation of
lines for GCA
Step-2
Production of the
synthetic
Step-3
Seed multiplication
Top cross or poly cross test for GCA;
outstanding lines selected as parents
Method-1.
•Equal seed from all the lines mixed and
planted in isolation.
•Open-pollinated seed harvested as the
synthetic variety (Syn1)
Method-2.
•The parental lines are placed in a crossing
block.
•All possible intercrosses are made.
•Equal seed from all the crosses mixed to
produce the synthetic variety (syn1)
•Seed of synthetic variety may be
multiplied for one or two generations
before distribution.
•Open-pollination in isolation (Syn1 or
Syn2)
STEPS INVOLVED IN PRODUCTION OF SYNTHETIC VARIETIES

49. Merits
•Offers a feasible means of utilizing heterosis in crop
species where pollination control is difficult
•Farmers can use the grain produced from a synthetic
variety as seed to raise the next crop
•In variable environments synthetics are likely to do
better than hybrid varieties
•Cost of seed in case of synthetics is relatively lower
than that of hybrid varieties
•Synthetic varieties are good reservoirs of genetic
variability
•Offers a possibility for continuous improvement of
varieties

50. Demerits
•Performance of synthetics is usually lower than
that of single cross and double cross hybrids
•Performance of synthetics is adversely affected by
lines with relatively poorer GCA. Such lines often
have to be included to increase the number of
parental lines making up the synthetics as lines with
outstanding GCA are limited in number
•Synthetics can be produced and maintained only in
cross-pollinated crop species, while hybrid varieties
can be produced both in self and cross-pollinated
crops

51. Breeding methods common for both self
and cross-pollinated
Introduction
Back cross method
Polyploidy breeding
Mutation Breeding
Transgenic breeding