1. Recurrent selection
schemes
SUBMITTED BY
J VENKATA YASHWANTH
TAM/2019-042
ACHARYA N G RANGA AGRICULTURAL UNIVERSITY
S.V.Agricultural college, Tirupati
Dept. of Genetics and Plant breeding
2. Idea of recurrent selection was first suggested by Hayes and Garber in
1919 and East and Jones in 1920
Recurrent breeding schemes were developed after 1945 when Hull
suggested that recurrent selection is useful to improve SCA
They are of four different types
Simple recurrent selection
Recurrent selection for GCA
Recurrent selection for SCA
Reciprocal recurrent selection
3. Simple recurrent selection
It was given by Sprague and Brown in 1930
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
4.
5. 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
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
6. Recurrent selection for GCA
It was first suggested by Jenkins in 1935
A tester with broad genetic base(OPV Synthetic) can be used for
evaluating lines for GCA
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
7.
8. 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
9. Recurrent selection for SCA
Recurrent selection for specific combining ability was proposed
by Hull in 1945
The main objective of tis is to isolate lie 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
10.
11. Reciprocal recurrent
selection
It was first proposed by Comstock, Robinson and Harvey in 1949
It is useful for both SCA and GCA
Useful for improving two source populations simultaneously
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
12. 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
III year – selfed seeds of I year from plants selected on basis of
evaluation o progeny is plants in sperate 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 – 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
13.
14. Comparison among different
recurrent selection schemes
When dominance is incomplete RRS and RSGCA would be
comparable and superior to RSSCA
When dominance is complete three methods are equally effective
when overdominance 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 dis equilibrium
If they are present then RRS is superior to both RSGCA RSSCA
Thus RRS is considered as superior to RSGCA RSSCA in al
practical situations
15. Merits
These recurrent selection schemes are useful for improving
desirable genes in population
It is useful in maintain high genetic variability in population due to
repeated inter mating of heterozygous lines
They can be used for developing synthetic varieties
Isolation of inbred lines from improved population
Maximum expression of heterosis can be seen in case of double
cross while isolation of inbreeds
16. Demerits
The major demerit here is it requires much efforts and
many recurrent cycles for population improvement
This method is directly not used in developing a new
variety
This method permits selfing which leads to loss of
some genetic variability