Considering Griffing's Method 2 and model 1,
xij = u + gi + gj + sij + eijkl
This model specifies two GCA's: gi and gj
However all papers I read specify only one GCA effect in the results.
How is this done?
Dear Ataguba,
First of all, on a simplify manner, you can "read" this model as:
Hybrid = Intercept + Parent 1 + Parent 2 + Deviation + Error
So, If you have 4 parents, you will calculate 4 GCA, one for each parent! For the crossing between 1 and 2, for example, the model should be:
Hybrid 1-2 = u + GCA-1 + GCA-2 + SCA-12 + error
A General combining ability of Parent 1 should be interpreted as the deviation of a Cross from the mean of all crosses when Parent 1 is present. This can be represented as follow:
GCA1 = Y1. - Y..
In which: Y1. refers to the MEAN performance of hybrids that has Parent 1 as one of the Parents; Y.. refers to the mean of all hybrids present on the analysis.
I hope to be helpful
Dear Ataguba,
First of all, on a simplify manner, you can "read" this model as:
Hybrid = Intercept + Parent 1 + Parent 2 + Deviation + Error
So, If you have 4 parents, you will calculate 4 GCA, one for each parent! For the crossing between 1 and 2, for example, the model should be:
Hybrid 1-2 = u + GCA-1 + GCA-2 + SCA-12 + error
A General combining ability of Parent 1 should be interpreted as the deviation of a Cross from the mean of all crosses when Parent 1 is present. This can be represented as follow:
GCA1 = Y1. - Y..
In which: Y1. refers to the MEAN performance of hybrids that has Parent 1 as one of the Parents; Y.. refers to the mean of all hybrids present on the analysis.
I hope to be helpful
Hi Ataguba,
As said by Rafael, we use the the phenotypic value of single-cross hybrids (progenies) as response variable to estimate the genetic merit of the parents (inbred lines) to select the best inbreds to keep in the heterotic groups. The general combining abilities (GCA) refers to the component of breeding values (pure heritable) of the hybrids (progenies) inherited from the parents (inbred lines). We define specific combining ability (SCA) as the effect that comes from all interaction effects between all alleles of the single-cross hybrids inherited from the parents. If we aim to exploit heterosis we may select by ranking the hybrids based on the SCA, and may choose to keep the parental inbreds of those hybrids. If we aim to just increase the pool of favourable additive effects in our germplasm, we may selected based on GCA. Observe that despise we use the phenotypic values of hybrids in the regression process, our aim is always select the best inbred lines based on the phenotypic performance of the single-cross hybrids (the product for farmers). This is the reason why you see frequently these reports on papers.
Best,
Dear Ataguba
You can use the online site ( the following link) to analyze diallel cross according to Griffing's Methods and estimate GCA and SCA.
http://14.139.232.166/opstat/dial.htm
Good Luck
The basic methods are explained in North Carolina model 1 and 2 ,3 and 4 based on which populations are being used. Di-allele or partial DA.
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