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Haploid Selection

Visual haploid selection is based on the expression of the kernel color marker R1-nj. In the presence of the dominant allele, the crown (aleuron layer) and the embryo of a kernel is colored. When a haploid inducer lines pollinates a donor plant, the resulting F1 seed will have a colored aleuron and a colored embryo. In about 10% of the pollinations, double fertilization fails and only the triploid endosperm is formed, whereas the egg cell remains unfertilized and a haploid embryo develops. As no genetic information of the haploid inducer is present in the haploid embryo, the embryo will remain uncolored.

Haploid selection based on R1-nj
Haploid selection based on R1-j expression in aleuron and embryo
Haploid selection in vivo
Kernels on an induced cob











In some genetic backgrounds, expression of R1-nj can be suppressed. For example, in the presence of the C1-I allele, selection based on R1-nj is impossible. But there are other factors that influence the R1-nj expression, which can lead to many false positives during visual haploid selection. In these populations, we rely on root color selection based on Pl1 expression, to sort out the hybrids seedlings. Continue...

induced ears with C1-I
Induced ears on a donor, heterozygous for C1-I, suppressing R1-nj expression in half of the kernels.
Red root selection
Haploid selection based on Pl-1: left hybrids with red colored roots; right haploid seedlings with uncolored roots