How can marker-assisted breeding remove flanking donor DNA while keeping the target gene?

When introgressing, for example, resistance genes from wild species, unwanted donor segments can hitchhike along with your gene of interest—a phenomenon known as linkage drag.

A structured marker-assisted breeding pipeline can help minimize this while retaining the resistance.

Here’s how:

1. Foreground selection:
Start by selecting individuals that carry the target gene itself using a trait-linked marker in the first round of backcrossing (Bc1). This ensures all selected plants express the desired trait.

2. Recombinant selection:
Use markers flanking the target QTL on both sides to identify recombination events. For example, if markers are 5 cM from the QTL, roughly 5 recombinants are expected per 100 individuals at the first backcross (BC1).

Step 1: Screen BC1 progeny for the trait marker, then select recombinants on one side of the QTL.
Step 2: In BC2, repeat the process on the other side to recover recombinants from that side.

3. Result: By combining foreground and flanking-marker selection, you retain the target gene while minimizing linked donor DNA.

💡Tip: The number of individuals to screen depends on the genetic distance of your flanking markers, and the optimal selection scheme should balance available genotyping resources and DNA extraction capacity.

Takeaway: Structured marker-assisted selection allows precise introgression of desired traits with minimal linkage drag, speeding up the development of improved varieties.

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How can marker-assisted breeding remove flanking donor DNA while keeping the target gene?

Increasing the precision in selection by targeting genes or genomic regions associated with those traits.

Allowing Early Trait Detection at the seed or seedling stage, saving time and resources.

Providing higher selection accuracy especially for traits whose expression is influenced by environmental factors or they are assayed by challenging protocols .

Accelerating breeding progress by enhancing selection accuracy and efficiency.