Mating Designs in forest trees –their importance, types and relative significance in genetic testing programmes.

1. Mating Designs (in forest trees)
–their importance, types and relative
significance in genetic testing
programmes.
1
BY:
SATYABRATA NAYAK
2015-17-013

2. What is mating design?
It refers to a system of crossing, which is used to
develop progenies of certain kind that serve to predict
the genetic worthiness of their parents.
Or ,
The methods by which trees are combined to produce
progeny is called as mating design.
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 Progeny testing
 Estimation of variance components
 Determination of GCA and SCA
 Creation of base population
 Determination of narrow sense heritability
 Estimation of genetic gains
Objectives of mating design:

4. Types of mating
design
Incomplete
pedigree designs
Only one parent
(usually the mother tree)
is known
Complete
pedigree design
Both the parents are
known
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5. A. Incomplete
pedigree design:
1. Open pollinated
mating
2. Pollen mix design
B. Complete pedigree
design:
1. Nested design
2. Factorial design
3. Single- pair mating
4. Full diallel mating
design
5. Half diallel design
6. Partial diallel design
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6. A.1. Open pollinated mating
• Trees are allowed to mate random through open
pollination
• Then seeds are collected and kept separate by family.
Collection of seed is generally followed by two methods:
o From Plus trees in natural stands or plantation
o From seed orchards
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7. Advantages:
1. GCA can be estimated
2. Helps in rogueing of genetically inferior trees
3. Advanced generation selection can be made
4. Provides estimates of additive gene variances and heritability
values
5. Easiest and least expensive
6. Used to quickly test selected trees
Disadvantages:
1. SCA cant be estimated
2. Limited utility for future generation
3. Possibility of selfing
4. Inbreeding depression
5. Lack of complete pedigree
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8. A.2. Pollen mix design
(Also called polycross design and sometimes topcross)
• Some trees are selected as male parents and their pollen (equal
quantities) are collected and mixed.
• The mixture is then applied to female parents
• Generally a considerable number of pollens are included in the
mix to insure that female parents are pollinated by a
representative sample of other parents
• No. of male parents should not less than 10
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9. Advantages:
1. GCA can be estimated
2. Additive gene variance
3. Heritability
4. Breeding value
5. Less expensive than other mating designs except open
pollinated mating design
Disadvantages
1. SCA can not be estimated
2. Breeding value may be biased
3. Advance generation selection is difficult
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10. B. Complete pedigree design
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B.1. Nested design
Also called hierarchial or North Carolina State Design 1
• Group of parents of one sex (male/female) are mated with to
members of other sex.
• Progeny produced is composed of both full-sib that have both
parents in common and half sibs that have only one parent is
common

11. Advantages:
1. It allows to estimate both additive and non-additive variances
and heritability
Disadvantages
1. GCA can be obtained only for members of rarer sex
2. Small no of unrelated family
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12. B.2. Factorial design
It is a modification of nested design
Also known as Tester or Line ˣ tester design and also North Carolina
State Design 2
• Here members of one sex are crossed in all combinations with
several members of the other sex
• Most commonly in forestry 4 to 6 parents designated as testers
are crossed with all other parents in the population .
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13. Advantages:
1. Very useful in progeny testing programme
2. Allows a reasonable estimation of variance components and
heritabilities
3. GCA and SCA can be estimated
4. Additive and non additive variances
Disadvantages
1. The number of parents that can be selected for the subsequent generation
will be limited to the number of testers
2. Small no of unrelated families
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14. B.2.b. Disconnected factorial design
Modification of factorial design
Breeding population is
divided into several sets of
parents and a factorial mating
design employed within each
set
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Advantages:
1. Maximize the no. of unrelated families
2. Good estimation of GCA and SCA
3. Good estimation of realized and expected gains that arise from
additive and non additive variation
4. Estimation of variance components and heritability
Disadvantages
1. Less efficient than the tester design for progeny testing
2. GCA is biased

16. B.3. Single pair mating
Each parent is mated to one
other member of the
population only once
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Advantages:
1. Creates the maximum no. of unrelated families in each
generation with a minimum no. of crosses.
2. Easy to carry out
3. SCA is estimated
4. Heritability and variance components are estimated
5. Complete avoidance of inbreeding
Disadvantages
1. Not suitable for roguing seed orchard
2. GCA and breeding value cant be estimated
3. Even number of trees required all time

18. B.4. Full Diallel mating design
• Each parent crosses to all
others in every combination
which involves direct
crosses, reciprocal crosses,
and all selfed plants.
• It is the most comprehensive
mating design available
• No of crosses = n², where n=
no. of parents
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Advantages:
1. Estimation of GCA, SCA
2. Maximum number of unrelated families
3. It is good to estimate all genetic parameters
Disadvantages :
1. Very cumbersome
2. No of crosses is very large
3. Time consuming
4. Costlier than all others
5. Rarely used in progeny testing

20. B.5. Half diallel design
• Modification of complete diallel
design
• Each parent is mated to every
other parent once as a male
parent only
• So there is no reciprocal crosses
made.
• If there is no need of selfed
crosses, such crosses are also
omitted
• So no of crosses will be
n(n-1)/2, where n = no. of
parents
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Advantages:
1. Good estimation of GCA ,SCA and genetic
parameters
2. Less expensive than full/ complete diallel
mating
Disadvantages
1. Not efficient as full diallel design
2. The no of crosses still large
3. Also rarely used

22. B.6. Partial diallel design
• Another modification of diallel design
• Only a portion of required crosses are made, that is each parent is
not mated to every parent in the orchard.
Partial diallel design again classified into ;
 systematic or progressive mating scheme
 disconnected diallel scheme
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23. B.6.a. Systematic or progressive mating scheme
• In this design crosses are made
that fall in particular diagonals.
• Diagonals are chosen so that no
one parent is involved in more
than few crosses
Advantages:
1. Maximum no of unrelated crosses
2. Estimation of GCA for each parent
3. Estimation of additive and non
additive variances
4. Estimation of SCA for a part of
possible combinations
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24. B.6.b. Disconnected diallel scheme
• In this design parents are
divided into small groups,
and diallel or half diallel
mating are done within each
group
Advantages:
1. This design maintains most of
advantages of more complete
diallel but greatly reduces the
number of crosses
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Mating design
Estimation
of GCA
Estimation
of SCA Estimation of genetic gain Cost
Open-pollinated Fair No
Gives information on realized and
expected gains
Very low
Polycross design Very good Not possible
Realized and expected gains
calculated from additive variance
Low
Nested design
Good for
rarer sets
Not good -do- Somewhat less
Factorial design Good Good
Realized and expected gains from
both additive and non additive
variances
Fair
Disconnected
factorial
Good Good -do- Fair
Single pair Not possible Good Good estimation of realized gains Very low
Full diallel Excellent Excellent
Good estimation of realized and
expected gains from additive and
non-additive variances
Very high
Half diallel Excellent Excellent -do- Very high
Partial diallel Good Good -do- Fair
Disconnected
diallel
Good Good -do- fair
Comparative efficiency of mating designs:

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 The genetic composition of the population can be
changed through selection and mating design
 Mating design helps develop progenies and provide
information about the nature of gene action
 Mating design are helpful in evaluating progenies and
selection of parents from the performance based on
GCA, SCA and nature of gene action.
 Mating design also help in creating variability and
thereby selection and advancement of subsequent
advanced generation
SUMMARY: