Still not sure the gene pool is important?

Look at the picture on the left. Sometimes, when you take two scrawny varieties of corn and cross them, you end up with a massive ear of corn.

This is hybrid vigor. The word hybrid means the plant was crossed and vigor means strong and healthy. The term is used when the crossed plant is superior to the parent plants.

Hybrid vigor is one reason that the genes of even worthless looking varieties can be very valuable.

Wild or less productive varieties can also carry genes for traits such as disease resistance or flavor. Breeders cross these plants with crop plants to develop better varieties.

Hybrids in Hawaii

What do you think is Hawaii's number one export crop? Pineapple, papaya, macadamia nuts?

Those are good guesses, but the right answer may surprise you. Hawaii's number one agricultural export is seeds. Seed companies like Hawaii because they do not have to stop planting during the winter season. Corn seeds from Hawaii are grown out to make more seeds which are then sold to farmers all over the world.

So, why do farmers buy so many new seeds? Why don't they just save their own seeds? The answer is hybrid vigor! Farmers buy hybrid seed so they can get bigger ears of corn like in the picture above.

These Punnett squares can show you how it works. We will look at only one gene to keep it simple. In real life traits are usually a combination of genes.

The seed company starts with two types of purebred corn. Purebred means both copies of a gene are the same. Lets say we are looking at a gene for how many rows of corn are on the ear. We can call it the "rows gene" and label it 'R'. Parent 1 has two identical copies of the 'R' gene. 'R''R' goes at the top of the Punnett square. Parent 2 has a different version of the "rows gene". To show it is different, we will label them little 'r'. We can say Parent 2 is 'r''r'. The genes for Parent 2 go on the side.

Click on the first Punnett square.

The seed company makes sure that Parent 1 can only cross-polinate with parent 2. Each new seed has one big 'R' and one little 'r'.

This is the hybrid seed. The farmer buys and plants these seeds. The seeds grow into strong plants with hybrid vigor that are very productive.

Now what happens if the farmer saves the seeds from his crop? The plants in his field all were from the 'R''r' seeds, so both parents of the next group of seeds have to be 'R''r'. We put an 'R''r' on the top and an 'R''r' on the side.

Click on the second Punnett square.

Seeds from this generation will have a mix of gene combinations, 'R''R', 'r''r' and 'R''r'. The farm will not be as productive.

Most corn growers buy new seeds each year to get the genes for hybrid vigor in every seed.

 

Learn more about Hawaii's seed crops.

Hawaii Seed Crops (National Agriculture Statistics Service, 2010)