What's the deal with bees?

[dakotajudo]

Right, most of our staple crops wind pollinate (nut trees, corn) or are capable of self pollination (legumes). But, self pollination can lead to generally lower yields and genetically inferior plants a few generations down the road.

That's not quite true.

First, corn yields decrease with success generations because of a loss of heterosis ("hybrid vigor"). Corn planted for production is hybrid - the seed comes directly from a cross between two pure-breeding parent lines. The hybrid is more vigorous than either of the parents.

But not all crops are produced as hybrids.

For example, wheat and soybeans are planted as purebreeding lines and are strictly self-pollinating (well, for all practical purposes), and you can generally replant for several generations without much loss of yield. In these lines, self-pollination maintains the purity of the cultivar.

There was some development of hybrid wheat lines in the 90s, but that didn't amount to much.

The farm I grew up on, we would buy seed for corn, but bin-run the small grains. Don't think I waw many bees out in the fields - it's pretty dry out here, I don't think they stray far from water.


The rise of GM crops is an indicative of the relative un-importance of insect pollination in crops. There are concerns that non-GM cultivars (or wild-type relatives) be contaminated with the artificial genes found in GM crops, so any GM crop in production has, so far, limited outcrossing. For these, bees are not an important part of reproduction.

Most of the soy bean farmers around here have bee hives along the edges of their fields when the plants are flowering.

I've never seen that here. In alfalfa, yes, but not soybeans.

I did my graduate work on soybean pod development, and I'd be (almost typed bee - ha ha) surprised if there were any type of insect pollination. Soybean flowers are cleistogamous - pollen is shed while the flower is still closed; to be honest, I don't think the flower even opens.

I've seen the soybean breeders in action and it does take some special skill to cross-pollinate soybean flowers; peeling open the flower without damaging the stamen and pistils.

I have this odd visual image of armys of migrant workers wading through the soybean fields armed with q-tips to pollinate the flowers.

When I was an undergrad, I worked for Pioneer Hi-breds. During the summer, they hired armies of student workers (this was Iowa) to do the opposite - pull the tassels off corn to prevent self-pollination. (This is how they produce the hybrid seed). Apparently, this job sucked, since the tassels are at the top of plants that can be 6-7 feet tall - lot of shoulder strain. I had a lab job - ha.

Anyway, I did a search in Crop Science for some background on alfalfa pollination, and ran cross this article:

"Diversity Pays in Crop Pollination"
http://crop.scijournals.org/cgi/content/full/40/5/1209