文档介绍：Chapter 10
Multiple Trait Selection
1
Strategies of multiple trait selection
Tandem selection
Selection in turn for each trait singly in essive generation
Independent culling levels
Selection for all traits at the same time but independently, rejecting all individuals that fail e up to a certain standard for each trait regardless of their values for any other traits
Index selection
Selection based on estimates of aggregate breeding values
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Aggregate breeding value
For n target traits, the aggregate breeding value of an individual is defined as
wi – weighting factor (relative importance) for trait i
often being economic weight: profit made from one unit change of trait i
ai – breeding value for trait i
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Estimation of aggregate breeding value
Aggregate selection index
xi – phenotypic value (single value or mean of several values) of the ith information resource on a information trait
bi – weighting factor (partial regression coefficient)
Principle for determining b’s:
To make the selection response for H maximum
to make rIH maximum
to make Var(I – H) minimum
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Construction of the index
B = diagonal matrix of additive ic relationship between the individual and all information resources
A = matrix of additive ic (co)variances between information traits and target traits
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Computing V
1. Diagonal elements (Var(xi ))
1)xi is a single record of an individual on trait T
2)xi is mean of n records of an individual on trait T
repeatability
3)xi is mean of single records of k individuals on trait T
phenotypic variance of trait T
additive ic relationship between individuals
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Computing V
2. Non-diagonal elements (Cov(xi,xj))
- xi and xj are phenotypic values of the same information resource on trait i and j
1) xi and xj are single records of an individual
2) xi and xj are means of n records of an individual
phenotypic covariance
phenotypic correlation
3) xi and xj are means of single records of k individuals
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Computing V
2. N