Diversity? Desirable or not.

[grunt]

I still wish I was getting into this sort of thing 30 years earlier in my life.

[raymondo]

Me too Dan!

[mnjrutherford]

I am nowhere near any of the rest of you on the scientific aspects of this issue. However, I rather wish that I was able to grasp the discussion at a slightly deeper level than I do.

I understand the need for diversity as it provides protection against epidemic. The most popular example being the potato famine.

For me personally, with corn. We grew 3 varieties last year, all within the same rows. Some crossing (obviously) occurred, but how much would be anyone's guess. We saved about a quart of seed from that field.

We have been told by our neighbors "nobody saves corn seed because it won't grow". I'm going to plant out a handful of this seed today mainly to test the germination rate but also to see if the commercial corn we planted actually has been rendered unviable or if the "normal" corn we mixed it with will allow it to germinate normally.

I also have several other "normal" corns that I intend to plant along with the seed saved from last year. My thought is to get a blend that will not resemble anything else from around this area and will be sort of exclusively ours. With the understanding of course that even though it is ours, the pollens will freely cross with anything else that comes close.

But is this a legitimate thought process? Will this protect our future with good corn or not?

[nuts]

fusionpower,
you're arguments are getting cofusing.
When we talk about diversity we should distinguish between diversity in the species as a whole and diversity within a subpopulation that does include only part of the individus within the species.This subpopulation can be the plants in your field.the plants cultivated in a region,or the few plants in you garden.
Of course the genetic diversity in a population is allways reduced compared to the species as a whole.This is a mathematical evidence,that would be stupid to deny.
So,in general,if you start breeding with fewer plants you will have less diversity,thus less traits to select on.
Paradoxally(if this word exists ;D),in terms of evolution,the separation of a species in different separated population creates diversity because every population will have selection for different conditions.And even if the diversity in populations can temporary decrease because of heavy selection,the total diversity of the species will increase.
That's how evolution works,and this mechanism is not different in nature than in cultivated species.

Untill recently,every cultivated species was divided in many subpopulations,in different climate,different cultural methods,and cultivated by people with different preferences,resulting in an fabulous diversity.We call those subpopulations varieties or cultivars.There are(were?)thousends and thousends of them for most cultivated species.
Over time,some populations will tend to dissapear when farmers replace there own seed with the better from abroad,but in general,the new genetics will mix with the genetics of the old population,so seldom there is a total extinction of a population.

But now we're in modern times.Only few vareties within most cultuvated plants are considered as worthwile,and these varieties wipe out all the vareties considered of less value.The extinction of populations becomes the rule instead of the exception,resulting in a loss of diversity.This is not a result of a 'breeding program' but the result of the fact that seed becomes a commercial product.This is a new form of selection,a selection between populations and not between individus.

Then,there are the 'breeding programs',that means,selection of a very few individus within a variety that are considered as 'the best' and eventually creation of crosses between vareties,but allways very few individus included.This is another bottleneck that is behind the loss of diversity within each population.

Do you want that?
Personally,I don't like the way it goes actually with biologic diversity and diversity of cultivated species in special.But everyone can have his opinion on this.The way you see this depends greatly on your ethical and/or political convictions.

But the case of corn is specially interesting.
Unlike beans,wheat and many other cultivated species,corn don't support inbreeding.
Because it needs much genetic diversity within the individu.
That means that you cannot select very few individus to create a very homogenous population with 'the best' genome.That works for many plantsspecies',but with corn you will get an inbreeding depression(less vigorous plants and less fertility)

This poses a serious problem for commercial plantbreeding.But(I don't know when)then someone invented the trick to overcome this problem:the F1 crosses.
If you create two varieties,with very homogenous genome,but suffering from inbreeding depression and make a cross,the plants will get back their original genetic diversity within each individu,but in each plant in the same way.
This way you can create a homogenous corn population without inbreed depression.

The breeders nightmare turned into a dream.Not only it became possible to create very homogenous cornpopulations.(and with corn f1's are easy to produce).
The farmers cannot reproduce this seed with the same result.The seed will give a very heterogenous population.
So,the farmer has to buy new seed every year!!

In my eyes Astronomy Domine is just in opposition to this method to create varieties that can be reproduced by the farmers themselves.It's a starting point to create more diversity.
To make the natural mechanism that create diversity working again.
Alan sends his seeds all over the world,and in every new place AD will develop in other directions,mix up with new genes,adapt to other climates,soils.

Well,I really don't know about my genes,but this is just what I learned at school ;D ;D ;D ;D

[DarJones]

Excellent post Nuts, and very well thought out. The only thing I would add to your points is that the true measure of increasing diversity is how much variation you start with and how much the population has increased. So using Astronomy Domine as a base, if the population increases by 1000 times, then the potential for diversity has increased proportionately. This is because three measures of diversity are affected. 1. The dispersal of a wide range of genetics. 2. The increase in potential for new combinations of genes. 3. The increase in potential for new adaptive mutations. And another major consideration is that it is being grown in a very wide range of new climates which will produce diverging adaptations over time.

I am deliberately taking a position opposite most of the posters on this board because it will bring out much more useful information than to have everyone agreeing. I happen to believe that maintaining diversity is vital to our future.

DarJones

[grunt]

Sometimes, as in this thread, the "Devil's Advocate" is a most valuable participant. Having read some of your other writings sometime in the past, I thought that might be what you were doing, Daryl.

[DarJones]

When it comes to genetics, our entire farming seed focus has been on increasing production which is extreme in the case of corn. Corn production has increased by 3200 percent in the last @50 years. Part and parcel with this increase in production is a decrease in diversity. Virtually all of the commercial corn produced today is based on the genetics of crosses between southern dent and northern flint corns dating to the 1800's. From that rather narrow pool of genetics, elite breeding lines have been sorted out and used in production of hybrid seed. This narrowed the genetic base on two counts, first because only southern dent and northern flint corns were used excluding many North American and all south american and tropical varieties, and second because the selection within the breeding population very narrowly selected for highly effective breeding lines in effect excluding the bulk of the diversity present in the parents population. The result of this highly efficient breeding work is that corn grown today has a genetic base nearly as narrow as the tomato (which is very highly inbred and has a very narrow genetic base).

Now think about the many diverse populations of corn that were available 100 years ago. They had been selected by local growers for local conditions in a range of climates. Some of the genetics involved are irreplaceable. There is absolutely no way to predict which genes will be most needed in the future. The only way to be certain we have the genes that will sooner or later be needed is to preserve everything possible.

Preservation efforts based on seed banks can be effective but seed are not readily available to the average person. In addition, seed bank populations are inherently limited in size and therefore tend to restrict diversity. The most effective way to preserve existing diversity and increase potential for development of variation in the future is to get as many people as possible to grow many different populations. The key here is that more plants will preserve more diversity.

Now I will give my answer to the question of Diversity, desirable or not? Diversity is not just desirable, it is vital to our future. It is the lynch pin that will enable us to make future improvements in production, disease tolerance, and other commercial traits that will be required. We don't just need to preserve some of the genetics, we need to preserve all that we possibly can. On a local basis, it is is desirable to reduce the level of diversity in order to concentrate a desirable trait. But on an overall level, we need to retain all the diversity we can stressing that diversity infers functional and potentially useful genetics. Please bear in mind that virtually all breeding programs that rely on selection for some specific trait(s) MUST reduce diversity.

Now the bad news, while I strongly support maintaining the diverse populations of corn plants found in the U.S., the tropical and south American corns represent a much greater genetic heritage for the simple reason that they come from closer to the point of origin of corn. Said another way, the corn we have in various gene banks in the U.S. represents only a small percent of the overall diversity present in zea maize. It is important, but arguably tropical and South American germplasm is more at risk and more likely to be lost over time.

So what role do I play in preserving genetics? I grow about 30 different heirloom vegetable varieties and send the seed to Sandhill Preservation. This ranges from the Black Peanuts to the White Whipporwill Cowpeas. This past year, I produced several gallons of Cherokee Squaw corn, about a gallon of Whipple White corn, and a couple of gallons of Oaxacan Green corn. It is not a major amount, but it does keep those varieties in circulation. I also grew another 2 varieties for personal use. This results in some interesting arrangements to prevent crosspollination. Most are based on time or distance isolation.

This year, I will be growing Buhl, Yukon Supreme, Whipple White, and Warners. I will grow for my own use about 3 other varieties, some of which are specifically to produce hybrid seed for further selection of traits I like. One of those is a result of a 1995 cross of Oaxacan Green with Hooker's Sweet corn. I hope to stabilize a good flavored green sweet corn.

DarJones

[DarJones]

Silverseeds, PM me your address. I think I have 20 or 30 seed I can spare if that will be enough.

DarJones