Why Hybrid Corn Seed Can’t Be Saved and Unintended Consequences
Hybrid corn seed cannot be saved and replanted because hybrid varieties do not “breed true” in following generations. The reason for this is that in the hybrid variety each plant had one gene from the male parent and one gene from the female parent for every plant trait. This is what produced the uniformity in maturity, height, etc. which was so beneficial for machine harvesting. But when the seed from a hybrid variety is saved and replanted, the resulting plants have a random assortment of gene pairs for each trait, producing plants of varying maturities, heights, etc. Thus the advantage of the hybrid variety is lost if seed is saved and replanted. The farmer needs to buy new seed every year in order to have the advantages of planting hybrid seed. Clearly the benefits of hybrid varieties were worth this extra cost to farmers as adoption of hybrid varieties was rapid. Farmers quickly developed loyalties to particular seed companies and varieties and paid premium prices for hybrid seed which continued to yield ever more bountiful harvests throughout the 1940s, 1950s and 1960s. There seemed to be no drawbacks to the use of hybrid corn seed.
A chink in the hybrid corn armor showed up in 1970. Aside from the obvious yield advantage, a big factor in widespread acceptance of hybrids was the uniformity which facilitated efficient machine harvest. However this uniformity has a pitfall. If a field is planted to one variety of hybrid corn all of the plants in the field are genetically identical. Therefore if one plant is susceptible to a pest, all of the plants are susceptible. The dangers of this genetic vulnerability can be mitigated somewhat by planting different varieties of hybrid corn in a given area or even in the same field. However in the 1960s another factor contributed to the genetic vulnerability of hybrid corn. The process of hand removal of tassels of female parents proved to be time consuming and expensive. Finding high school youth willing to spend their summers trudging up and down corn rows in the heat of the summer in Illinois and Iowa became more and more difficult. When a breeding technique was developed which incorporated male-sterile cytoplasm into female parent lines it was quickly adopted by the seed companies. There was no longer any need to pay people to hand remove the tassels. Unfortunately there were only a few sources of male-sterile cytoplasm and by the late 1960s approximately 80% of the hybrid corn varieties were developed using a line known as Texas Male-Sterile Cytoplasm (T-Cytoplasm). In the crop production year of 1970 a perfect storm developed with the occurrence of a particularly virulent strain of the fungal disease Southern Corn Leaf Blight (SCLB), warm moist weather conditions that favored SCLB, and susceptibility to SCLB in all hybrid corn varieties developed using T-Cytoplasm. Many acres of corn production were lost as a result. “In August 1970, Illinois Secretary of Agriculture John W. Lewis was estimating that 25 percent of his state’s corn crop was already lost to the blight. Just one year earlier, Illinois had been the nation’s top corn producer, accounting for more than one-fifth of the crop.” http://www2.nau.edu/~bio372-c/class/sex/cornbl.htm
In the aftermath of the 1970 debacle the seed companies reverted to using hand removal of tassels until new lines of male-sterile cytoplasm were developed. But a hard lesson had been learned by corn farmers and they would never again have quite the same level of trust in hybrid corn as they did before 1970. Herbivore Reed
Next: Why there may be a place for open pollinated corn varieties
Corn, Zea mays, which most of the world outside of the United States knows as maize, is one of the most useful cereal crops of the world. Today in the United States and much of the developed world, corn is mostly fed to animals. But historically in the United States corn was a major source of direct sustenance for humans as it still is today in much of the developing world .
To understand the open pollinated corn story we need a little corn botany and genetics lesson. Sorry, you may stop reading now and wait for the next post if this makes your hair ache. Corn is a monoecious plant. That is, it has separate male and female flowers on the same plant. The tassel is the pollen producing male flower and the ear with silk is the female flower. (See diagram link) Corn is wind pollinated and normally it is cross pollinated, that is, pollen from another plant pollinates the female flower on a given plant. This process of natural pollination by the wind resulting in cross pollination of individual plants is sometimes referred to as “open pollination”.
Until about 1930, all of the corn grown in the United States and elsewhere was from seed which had been produced by this process of open pollination. Individual open pollinated varieties of corn had a great deal of genetic variability. That is, although individual plants within a variety looked a lot alike and had similar growth characteristics, each plant actually was unique and had a slightly different mix of genes from every other plant. In the early twentieth century corn breeders discovered that if they developed two inbred lines of corn and then crossed (hybridized) them, the resulting seeds would produce plants that were more robust than either of the two parent plants, a phenomenon known as hybrid vigor. If the breeders produced many plants of the two inbred lines and crossed them, the resulting seed could be used to plant acres and acres of corn that was not only robust, but each plant was genetically exactly like every other plant. That meant the plants would all grow at the same rate, mature at the same time, and grow to be the same height, assuming similar environments. This was ideal for machine harvesting of corn. Furthermore, these hybrid varieties, as they were known, had surprisingly higher yields than the old open pollinated varieties from which they were derived. The harvest advantages and yield advantages combined made hybrid corn varieties very attractive for farmers, despite the fact that the seed was expensive and new seed had to be purchased each year (More on this in the next post). By 1950 nearly all of the field corn and sweet corn produced in the United States was hybrid corn, truly an agricultural revolution.
The production of hybrid seed was fairly simple in theory, but quite labor intensive in practice. Rows of male parent plants had to be planted next to rows of female parent plants. The tassel needed to be removed from the female plants to make sure that only the pollen from the selected male parent pollinated the female parents. Resulting seed was then harvested from only the female parents. To avoid damage to the female plants, the tassels had to be removed by hand. And the kicker was that this whole process had to be repeated every year as grain from a hybrid variety could not be saved and replanted the following year. Very quickly many high school students in the Midwest had a guaranteed summer job. All you had to be willing to do was walk up and down miles of corn rows in the hot sun removing tassels. – Herbivore Reed
Next: Why Hybrid Corn Seed Can’t Be Saved and Unintended Consequences
Corn Diagram Link:
To read more about the history of hybrid corn:
2009 was, for me, the year of the mouse melon. You can read my previous post in which I enthuse about this little crisp cucumber relative that looks like a miniature watermelon.
So if you want 2010 to be your mouse melon year, order your seed now. You’re not likely to find this one at your local garden center (unless you urge them to carry it!), but a number of seed companies do have it. The most likely way to find it is to search under “Mexican sour gherkin” as that’s the most-often used name in the seed industry.
Here are some catalogs I’ve found that carry Mexican sour gherkin seed.
(Grow It Eat It and University of Maryland Extension do not endorse any business or prefer one over another; this is for information only. But I do personally know each of these companies to be reliable.)
It’s cold outside, more snow is on its way, and spring planting is just a dream. But the seed catalogs are here, so dreaming is the right thing to do… and then, for those of us who have a budget at least, more serious planning.
I have my own small garden to plan, but also I’ve got 1700 square feet of demo garden to play with: maps to draw, leftover seed to organize, new seed to order. I’ll be making some posts along the way to let you in on some of my choices.
First, how to choose between all those deliciously attractive catalogs that are beating their way to your mailbox? (Or if they aren’t, everyone’s got a website these days.) In the end, it’s a matter of personal choice, but here are some things I look for in a catalog or website – and don’t necessarily find them all in one place!
Also, consider that seed produced here on the East Coast (ideally in the Mid-Atlantic) may grow better for you than seed from elsewhere in the country that’s meant to do well in other climate conditions. “Buy local” doesn’t mean quite the same thing with seed that it does with produce from a farmer’s market, but you can keep it in mind anyway. And even though you may want to get your orders in now to be sure you get exactly what you want to grow in 2010 (yes I will tell you in another post where you can order mouse melon seed!), remember that your local garden center will have that seed you forgot to buy come spring.
What do you look for in a seed catalog? What are you going to order this winter?
I love Fall broccoli. Maturing as the weather gets cold gives it a milder flavor than spring broccoli that matures as the weather gets hot. Fall broccoli also has fewer pest problems. And I enjoy harvesting fresh vegetables from the garden in December.
Fresh eggs taste best on winter mornings.
1 frozen pie crust
4 eggs and 4 egg whites
1 cup chopped broccoli steamed for 5 minutes
Medium size onion or 2 scallions, slivered
1 cup shredded cheddar cheese
Salt and pepper
Preheat oven to 350 degrees. Hold back ¼ cup of the cheddar cheese and whisk together all other ingredients. Pour into the pie crust and sprinkle the remaining cheddar cheese on top. Bake on lower rack in oven for 35 minutes or until set. You can substitute spinach for broccoli and add ham if you want.
Zoom in for a mouthwatering look.
Maybe we’ll leave a quiche for Santa instead of cookies.
We don’t usually garden into December at the Derwood Demo Garden, but this fall we’ve been short on work days because somehow it always rains on Thursday, and so a lot that would normally have been harvested in the vegetable garden is still there. And – I went to visit today to see how things were after the snow and before tonight’s predicted freezing rain – much of it is still looking great!
Here’s what I harvested today:
The cauliflower is still under a row cover that was meant to protect it from insects (mainly harlequin bugs) and is now offering some small protection from weather. There’s a Lesson Learned story connected with that row cover: I bought the cauliflower seedlings in August and put them in the ground, checking them (I thought) carefully for pests and covering them up. But the next time I looked at the plants, they had been nearly skeletonized by cabbage worms. Missed a couple – or the eggs. Lesson: do not put the pests with your plants under the row cover. I squished all the caterpillars I could find, and the next time I looked (a couple of weeks later, due to circumstances), the plants were at least in no worse shape, and one lone cabbage butterfly fluttered out. But I can’t imagine most of the butterflies got through their life cycle very well imprisoned under a row cover. At least no harlequin bugs found their way in, and the cauliflower started looking better as soon as the temperatures cooled. We’ll have to work harder on stimulating head formation, so it’ll be all worthwhile!
Maybe we’ll do this fall gardening thing on purpose next year, hm? It seems to work!
Container gardening is possible well into the fall. I tried it for the first time this year with good results. In early September I planted endives, a lettuce mix, and arugula in large plastic pots using a mixture of commercial potting soil and compost. The pots are on a sunny, south-facing patio. I began picking a few leaves by mid-October. Now it’s the first week of December and I’m still harvesting enough greens for salads by cutting rather than pulling up the plants. And the leave continue to regrow — admittedly slowly but still there’s new growth. With regular frost likely in the coming weeks, I plan to move the pots soon up against the south-facing wall of the house to extend my container gardening a bit longer.
I also planted kale in a similar large pot (foreground)in early September. This pot will go up near the south wall as well with the seedlings protected with light straw. To get a head start on spring gardening, I will set the well-hardened kale seedlings out in the garden in mid-February or when the frost is out of the soil.