Diallel selective mating

2.  Accumulation of desirable alleles in a population
through various breeding techniques is known as
population improvement.
 Those breeding procedures used for population
improvement are called population improvement
approaches.
 4 approaches:
◦ Recurrent selection
◦ Disruptive selection
◦ Diallele selective mating
◦ Biparental mating

3.  Proposed by Jensen in 1970 for genetic improvement
of wheat
 Now used in various autogamous crops esp. small
grain crops viz., wheat, barley, rice etc.
 Provides 3 basic functions of a versatile breeding
programme
1. Allows developement of F2, F3, etc (selfing series )
at every stage of breeding programme - permits
isolation of purelines for use as commercial varieties

4. 2. Requires intermating among selected plants/lines in
each stage – progenies form next stage of selfing
series, ie., breeding programme progresses in two
different directions : vertical & horizontal
3. Can introduce new germplasm at any stage of the
programme by intermating it with some of the
selected parents of that stage – permits retention
and/or creation of variability for effective selection
& introduction of new genes as breeding material as
and when desired.
 Was not widely used - difficulties in making large
number of crosses - Jensen suggested use of GMS to
overcome this difficulty

5. 1. Application: Effective for improving autogamous
species which are difficult to cross & have few
seeds per cross – small grain crops – supplements
conventional breeding in SP crops.
2. Approach: Considered as a form of recurrent
selection as it involves selection & intermating in
segregating generations. Both mass and recurrent
selection procedures used for handling of material
in this system – permits use of conventional
breeding and improvement of population by
intermating.

6. 3. Advantage: Superior/promising genotypes
identified and isolated for dvpt of new cultivars at
any stage – permits extraction of new cultivars at
various stages & also incorporation of new
germplasm at any stage.
4. Parents involved: Permits inclusion of multiple
parents (Conventional breeding – two parents).
5. Goals: Fulfils short & long term goals – permits
use of conventional selection procedures at any
stage & broadens genetic base of populations.
6. End Product: Used as pureline variety, mass
selected variety or as parental lines in breeding
programme.

7.  Consists of 3 major steps:
1. Parental Diallel Series
2. F1 Diallel Series
3. Selective Mating Series
DSM is defined as a method of population of
autogamous species that involves parental diallel
species, F1 diallel species and selective mating
series in the breeding procedure.

8. 1. Parental Diallel Series:
◦ Parental lines selected keeping in view the
breeding objectives.
◦ Selected parents crossed in diallel fashion & F1
seeds obtained.
◦ No. of parents ≤ 7 – complete diallel used
◦ No. of parents ˃ 7 – partial diallel used
◦ Designated as P1

9. Complete diallel
Each parent crosses to all
others in every
combination-direct,
reciprocal crosses &
selfed plants
Partial diallel
Each parent mated to
every other parent once
as a male parent only –
no reciprocal & selfed
crosses

10. 2. F1 Diallel Series:
◦ F1 crosses used in two ways:
i. To produce F2 population
ii. To develop F1 diallel series
◦ Mass selection-to advance the F2
population
◦ Selected F1 crosses crossed in diallel
fashion
◦ Aka multiple parent crosses – each
cross involves 4 parents
◦ Designated as P2

11. 3. Selective Mating Series:
◦ F1s from multiple crosses
selfed to produce F2
population
◦ F2 population used in 2 ways:
i. To produce F3 population
by mass selection
ii. To develop first selective
mating series (P3 ) by
intermating selected F2
plants

12.  F1 crosses developed by selective
mating used in 3 ways
 Some selected for intermating to
form second selective mating
series (P4 )
 Others crossed with new parents
(germplasm lines) not included in
original diallel
 Some plants selfed to develop F2
generation
 Many such cycles required to
achieve desired breeding
objective.

15. Merits:
 Useful in broadening genetic base of populations by
incorporation of multiple parents (germplasm lines)
in breeding programme.
 Helps in breaking undesirable linkage blocks –
permits intermating of selected plants in segregating
generations –enables additional gene recombination.
 Results in vast genetic variability for various
economic characters – due to incorporation of
multiple parents & intermating in segregating
populations.
 Effective in developing new cultivars in small grain
crops.

16. Demerits:
 Large number of crosses required to obtain sufficient
quantity of crossed seeds- difficult task without use
of MS.
 Involves handling of material by mass selection &
intermating in segregating population – require more
space and labour.
 Less effective in improving characters with low
heritability.
 Rarely used in crop improvement & has not become
popular so far.