In this demonstration you will use the breeder’s equation to evaluate two specific breeding schemes. The breeding schemes are similar, the only difference being the number of selfing generations used in line development prior to testing and selection. More selfing generations increases the additive genetic variance among lines, which is favorable for genetic gain. On the other hand, more selfing generations increases the length of the breeding cycle, which is unfavorable for genetic gain per unit time.

Consider the following breeding scenarios :

Imagine that you are already implementing Scheme A and therefore you have data to be able to estimate genetic variance among F4 derived lines (\(\sigma^2_{f_{4:5}}\)), error variance (\(\sigma^2_{\epsilon}\)), and genotype-by-environment interaction (GxE) variance (\(\sigma^2_{I}\)). Suppose these estimates are \(\sigma^2_{f_{4:5}}= 0.3\), \(\sigma^2_{\epsilon}= 0.5\), and \(\sigma^2_{I}= 1\). Also suppose that you can evaluate lines in two environments and you will replicate each line twice within each environment.

Exercises

Use the information just provided to answer the following:

1. What is the expected genetic variance among F3 derived lines?

2. What is the selection accuracy among a) F4 derived lines and b) F3 derived lines?

3. Based on the breeders equation, would it be better to derive lines from the F3 or from the F4?