Dr. NAVEENKUMAR K.L Assistant Professor (GPB)

1. Recurrent selection
Dr. NAVEENKUMAR K.L
Assistant Professor
Dept. Of Genetics and Plant Breeding
UAHS Shivamogga

2. Terminology
 Combining Ability (CA): refers to the capacity or ability of a
genotype to transmit superior performance to its crosses.
 The concept of CA as a measure of gene action in maize was
proposed by Sprague & Tatum (1942).
 General Combining Ability (GCA): Average performance of a
strain/genotype/inbred line a series of hybrids/cross
combinations.
 Estimated from the performance of F1’s from the crosses.
 GCA estimated from half sib families.
 Specific Combining Ability (SCA) : the performance of a
parents in a specific cross.
 Refers to the deviation of a particular cross from general
combining ability.

3. Full sib: Progeny of the mating of two individuals/ parents.
Half sib: Progeny having one parent in common.
Tester: A common parent mated to a number lines/ strain /
plants.
Open pollinated variety: variety developed in cross
pollinated species, pollination occurring naturally without
restriction.

4. GENETIC BASE:
 Genetic Base: The amount of genetic diversity available in a breeding
population is referred to as genetic base of that population.
1. Broad genetic base:
Plant populations that are composed of several pure lines, inbred lines
or heterozygotes and homozygotes are said to have broad genetic base.
Examples: Mass selected varieties, multiline varieties, synthetics,
composites and land races.
2. Narrow genetic base:
Those plant populations that have been developed from single
homozygote or heterozygote are-said to have narrow genetic base.
Examples: pure line variety, varieties developed by backcross, pedigree
method bulk method, and single seed decent method, clonal variety

5. INTRODUCTION
 Idea of recurrent selection was first independently suggested
by Hayes and Garber (1919) and East and Jones (1920).
 The procedure of recurrent selection described by Jenkins
(1940).
 The term recurrent selection given by Hull (1945).
 It is a cyclic selection that used to improve the frequency of
desirable alleles for a character in breeding population.

6. DEFINITION:
Hull defined recurrent selection as reselection generation after
generation with inbreeding of selects to provide for genetic
recombination.
Recurrent selection is defined as reselection generation after
generation, with inter-mating of selected plant to produce the
population for the next cycle of selection.
The idea of this method was to ensure the isolation of superior
inbreds from the population subjected to recurrent selection.

7. The isolation of an outstanding inbred line depends on two
factors:
1) The proportion of superior genotypes present in the base
population from which lines are isolated.
2) The effectiveness of selection during the inbreeding of
desirable genes.

8. TYPES RECURRENT SELECTION
1. Simple Recurrent selection (SRS)
2. Recurrent selection General Combining Ability (RSGCA)
3. Recurrent selection Specific Combining Ability (RSSCA)
4. Reciprocal Recurrent selection (RRS)

9. Simple recurrent selection
It was given by Sprague and Brown in 1930
A type of recurrent selection that does not include tester
is referred as simple recurrent selection.
It is also known as phenotypic recurrent selection.
This method is an extension of mass selection.
The selection based on phenotype.
This method is useful only for those character which have
high heritability.

10. A number of plants with desirable phenotype are
selected and self pollinated.
In second year separate progeny rows are grown for
selfed seeds
Progenies are inter crossed by hand in all possible
combinations and equal amount of seed from each is
composited to raise next generation
For first recurrent cycle the same process is repeated
but this time with composited seed

13.  Recurrent selection is effective in increasing the frequency of
desirable genes in the selected population.
 Suited for highly heritable characters.
 In some cases we can see large variability than population.
 Recurrent selection is considered to be more effective than
selection with self-pollination.

14. Inbreeding can be kept low by following ways
1.Population from inter crosses is may be allowed to mate
random for one generation and the seed is subjected to
reselection
2.Each intercrops maybe grown separately and it should be
ensured that selected plants are not related by any
parentage

15. Recurrent selection General Combining Ability (RSGCA)
It was first suggested by Jenkins in 1935
A tester with broad genetic base (OPV Synthetic) can
be used for evaluating lines for GCA

16. PROCEDURE
 I year – phenotypically superior plants are selected from
population and selfed seed are harvested separately.
 The selected plants are crossed with tester and the seed are
harvested individually.
 II year – replicated yield train is conducted using self crossed seed
and superior progenies are identified.
 III year – the selfed seed of from first year of superior progenies in
RYT are planted in separate progeny rows and inter mated in all
possible combinations.
 Equal amount of seed is composited from each inter cross and
used to raise next generation

17.  IV year – composited seed are planted phenotypically
superior plants are selected selfed and intermated with a
tester and harvested individually.
 V year – test crossed seed are plants in sperate progeny rows
superior progeny are identified
 VI year – same process of third year completes first recurrent
cycle
 If necessary second and third recurrent cycles may be
initiated
 It may be used to improve yielding ability of population and
at end product may be released as synthetic variety
 May be useful for increasing the frequency of desirable
genes in the population and isolating superior inbreeds

20. Recurrent selection Specific Combining Ability (RSSCA)
 Recurrent selection for specific combining ability was proposed
by Hull (1945).
 The main objective of this is to isolate line from population that
would combine well with given inbred useful for selecting lines
for SCA.
 The procedure for recurrent selection is identical to that of
RSGCA.
 Only difference is here we use inbred as tester which has
narrow genetic base.

21. Inbred line

24. RECIPROCAL RECURRENT SELECTION (RRS)
 It was first proposed by Comstock, Robinson and Harvey (1949).
 To select for both general and specific combining ability.
 Useful for improving two source populations simultaneously.
 Although Recurrent and Reciprocal Recurrent Selection methods
were originally designed and used to improve the chances of
developing superior inbreds of corn, these procedures are not
used explicitly in private industry for that purpose today.

27. PROCEDURE :_
I year – two source populations are taken and
phenotypically superior plants are selected from each
population and selfed.
Each of selected plant from A is random mated with
plants in B.
Selfed seed are harvested separately and used for
planting in III year.
Top crossed seed from each plant is harvested
separately.
 II year – two replicated yield trails are conducted
progeny rows of test cross seed of population A and B
are grown separately
 Plants producing superior progenies are identified

28.  III year – selfed seeds of I year from plants selected on basis of
evaluation of progeny is plants in separate rows in two crossing
plants .
 All possible inter crosses are made among the progeny rows in
each plot are made and equal amount of seed from all inter
crosses from crossing plots A is mixed to raise source population of
A for next year and similarly with B crossing plot .
 IV year – source populations A and B are raised from composited
seed of a and b and same operations of first year re repeated.
 V year – tested seed as same in second year are planted and
superior progenies are identified .
 VI year – same as third year where A and B are plants in different
crossing blocks selected one are inter mated and seed is
harvested.

29. Genetic basis of recurrent selection
Comparison among different recurrent selection schemes.
 When incomplete dominance is their RRS and RSGCA would be
comparable and superior to RSSCA.
 When complete dominance is their three methods are equally
effective.
 when over dominance is seen the RRS and RSSCA would be
comparable and superior to RSGCA.
 The above statements are true in absence of epistasis multiple
alleles and linkage disequilibrium.
 If they are present then RRS is superior to both RSGCA RSSCA
 Thus RRS is considered as superior to RSGCA RSSCA in all
practical situations.

30. Merits
1. These recurrent selection schemes are useful for improving
desirable genes in population.
2. It is useful in maintain high genetic variability in population
due to repeated inter mating of heterozygous lines.
3. They can be used for developing synthetic varieties.
4. It helps in breaking repulsion phase of linkage.
5. Isolation of inbred lines from improved population .
6. Maximum expression of heterosis can be seen in case of
double cross while isolation of inbreeds.

31. Demerits
1. The major demerit here is it requires much efforts
and many recurrent cycles for population
improvement.
2. This method is directly not used in developing a new
variety .
3. This method permits selfing which leads to loss of
some genetic variability.

32. Recurrent selection has been successfully used
for the improvement of oil content in maize, fibre
strength in cotton and sugar content in sugarbeet
and sugarcane.