Breeding a Patriotic Sweet Corn

I do like sweet corn. I grew up on Golden Bantam, the classic open-pollinated yellow corn and Stowell's Evergreen, a great tasting but late ripening white corn. We grew both side by side and produced a nice bicolor corn in the earliest ripening Stowell's Evergreen if there was still a Golden Bantam shedding pollen. First the yellow Bantam would ripen, then we would get the bicolor cobs (only in some years), and finally, usually in late summer, those big sweet pure white Evergreens.

SWEET CORN (Zea mays) family: Poaceaceae

SWEET CORN (Zea mays) family: Poaceaceae

It was fun to see the yellow kernels that showed up in the earl white ears of the Evergreen. Since the gene for white kernels is recessive to yellow, when a single pollen grain from the Golden Bantam made contact with a single silk on the ear of Stowell's Evergreen, the one kernel on the cob attached to that silk will mature yellow. Basic corn reproduction requires pollen from the tassel which contain the male flowers (essentially, just an anther) to fertilize the kernels of the ear, each kernel being a one-seeded fruit. The corn cob holds hundreds of female flowers consisting of just the ovary (kernel) and attached silk (a very long stigma). It takes a lot of pollen to develop a full ear of corn but the corn tassel with all of those dangling anthers can release to the wind an unbelievable quantity of pollen usually in the late morning when humidity lessens. The ears being fertilized depends only on which direction the wind is blowing at the time the silk is receptive to the pollen and the tassels are shedding the pollen. That's why corn is planted in blocks instead of long single rows. No matter which direction the wind is blowing, there is more of a chance that pollen will be transferred to ears in a block.

Collecting Pollen

Collecting Pollen

Trim the ear silks so they are even with the tip of the husk...

Trim the ear silks so they are even with the tip of the husk...

Preventing stray pollen from fertilizing ear using ear bag...

Preventing stray pollen from fertilizing ear using ear bag...

Pollen collected in a pitcher

Pollen collected in a pitcher

...then apply the collected pollen)

...then apply the collected pollen)

...or plastic cup

...or plastic cup

Breeding Patriotic Sweet Corn

The red anthers from Painted Hills Corn are shedding pollen.

The red anthers from Painted Hills Corn are shedding pollen.

On a whim, my son brought up the idea of breeding a sweet corn which would have kernels of red, white and blue (presumably for fourth of July picnics). I have grown sweet multicolor corns before. Native Seeds/SEARCH, Tucson, AZ has a nice collection of sweet corns that were grown by miners in New Mexico and Colorado and survived to the present thanks to Indian seed-savers. I also have grown Peace Seed's "Rainbow Sweet" bred by Alan Kapuler. I explained to Zak that producing an American flag in a husk was probably not possible. Based on my experience, maybe he could hope for mahogany/orange, creamy white and a kind of blue-gray blend. To prevent a muddiness in color I suggested that we breed a "red" corn and a separate "blue" corn. A new offering by Fedco Seeds is one of Alan Kapular's crosses between Painted Mountain Indian Corn and Luther Hill Sweet Corn (Painted Hills). It has nice red and blue kernels that we can separate out of the packet of seed and I like the description that tells of it's tight husks that resist earworms. Since Zak is partial to the flavor of the sweet "se" corns, we'll use a blend of hybrid white "sugar enhanced varieties as a parent.

In May, 2005, we planted our selected "reds" in alternate rows with a mix of homozygous "se" white sweet corns. In another block we planted our selected "blues", again with alternating rows of the "se" white mix. We used homozygous "se" types to have a better chance of transferring the "se" gene to the offspring. Using more than one variety of white corn gives us a greater chance that one of the white hybrids will mature at the same time that our Painted Hills reds and blues will and adds to the number of crosses we can evaluate.

It's no hassle to de tassel. Just grab the top and when you see the tassel beginning to appear

It's no hassle to de tassel. Just grab the top and when you see the tassel beginning to appear

We'll use the Painted Hills as the male parent and detassel the hybrid whites. Without hybrid white pollen, the ears of the white se types should produce mostly reds or mostly blue kerneled cobs since both colors are dominant over white kernel color and those colored kernels should all contain the "se" gene for extra sweetness and tenderness. We'll also get a crop of Painted Hills. A selection of blues or at least mostly blue kernels from our blue corn block and a selection of mostly reds from our red corn block. The ears will reveal the degree of success shortly (they're just beginning to tassel as I write this).

When the red and blue kernels from this year's crop are planted next year we should see red and blue kernels on the cobs produced and also white since the recessive whites will show up in the next generation. The same thing happens when you plant hybrid bi-color corn. You plant only yellow kernels but harvest yellow and white corn. Also, the colors will be muted during the edible "milk" stage. Bright colors develop mostly after the corn matures and passes the edible stage. Corn is fickle though (the complex genetics of coloration in Indian Corns and "se" hybrids don't help any) and I don't presume this experiment will work as well as Zak expects.

Nevertheless, this kind of breeding challenge is what makes gardening fun.

Incredible simulated patriotic corn, a must for Fourth of July or Bastille Day for those with shorter growing seasons.

Incredible simulated patriotic corn, a must for Fourth of July or Bastille Day for those with shorter growing seasons.

To produce controlled crosses between corn plants or a self-pollination, collect pollen. I'm using a glass pitcher placed over a shedding tassel. Shake the tassel to collect the yellow pollen. Note the contents of the pitcher in the photo (left) showing some of the anthers and about a zillion yellowish-white pollen grains coating the inside glass.

To prevent stray pollen from fertilizing kernels of a developing ear slip an ear bag over the ear before silks can be seen. Ear bags can be purchased from Southern Exposure Seed Exchange, Mineral, VA. You can also use an inverted cup which is effective if it stays in place.

When the silks emerge an inch or so and while they are fresh and moist either dust the silks with the collected pollen. Each silk is receptive to pollen grains over it's entire length.

An especially effective technique involves cutting the silks even across the top of the ear husk. With your finger or a brush wipe an ample amount of pollen over the dense cut surface of the silk.

Replace the bag or cup and allow it to remain on the ear until the exposed silk loses it's moisture and begins to dry. At that time the silks won't be receptive to stray pollen.