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Ames, IA | So, the easy way to explain this is through the basics of corn genetics. Each corn plant has 10 pairs of chromosomes, with one chromosome of each pair coming from the mother, and the other coming from the father. In this way, hybrid seed can be visualized from parents A and B as being AB, as opposed to AA or BB for the parents. Bringing in the second hybrid, CD (since it has different parents), would result in a mix of plants that are AC, AD, BC, and BD for any particular region of the genome. As such, there will be immense genetic variation (think: plants that are three feet tall next to 10 feet tall plants), making plants compete with each other and leaving a mess to deal with come harvest. The other problem is that parents A and C in this example are in the same heterotic group, and B and D are in another. The majority of today's corn yield come from the crossing of separate heterotic groups, with something like 60% of total yield coming from heterosis, or hybrid vigor, which is the result of having two unique alleles at a particular locus. If these spots in the genome that contribute to heterosis are coming from parents in the same heterotic pool (AC, BD), they are highly unlikely to still be different, reducing overall yield. | |
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Corn Breeding Question
