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Anchorage, Alaska

What would be the expected outcome of successive selfing for 3 generations. For example selfing the offspring of 1725 Harp. I'm a newbie and seeking information. Would continual inbreeding have the same result as cousins marrying cousins repeatedly? Or am I missing some vital understanding of pumpkin genetics?

11/15/2010 2:40:17 PM

Colorado

sherm ,if the initial selfing resulted in the traits you were after, then a second selfing should lock those traits into a consistent seed stock.The third selfing would be very similar to the second. There can be some real surprises in the first generation.

11/15/2010 2:47:34 PM

Deer Park, WI

Selfing is a "purification" process. It is the quickest path to consistency that one can employ in the breeding process.

There is no way, with current abilities, to predict what would happen if you selfed 1725 for three generations. Foremost, we as growers do not know which characteristics of interest are genetically controlled (size, % heavy, etc). Secondly, we do not know which genetically-controlled characteristics are based on recessive and dominant genetics.

The 1725 may have a recessive characteristic that, when selfed repeatedly, may demonstrate itself. This characteristic could be good or bad...we simply do not know.

Outcrossing, as growers typically do, minimize the likelihood of recessive trait expression. Unfortunately, most associate recessive trait expression and the selfing process as a potentially negative outcome. This is not true, there is equal chance for a positive outcome. And as I stated, it is the only way to preserve a specific desireable trait, assuming it is gentically controlled.

Bottom line is that there is so much we do not know about genetics. But we do know that selfing preserves characteristics that are genetically controlled. It is also the only path to exploring the potential of hybrid vigor in C. maxima

11/15/2010 4:29:59 PM

Pocatello (cliffwarren@yahoo.com)

If we were to list the "things we know" about genetics and the "things we don't know", the don't know list would be quite a bit longer.

For example, we might say that pumpkins are an outbreeder because their flowers have either male or female parts, not both. (Usually not both, I've seen otherwise!) This suggests an outbreeder, but is it only that the flowers are outbred? That is, in nature, if you just let the birds and bees do the pollinating, two-thirds of the time it's likely going to be what we would call a "self" pollination.

Then you move into the train of thought that every grain of pollen and every future seed is genetically different, and it starts to make your head spin.

We see it all the time, where a fruit ought to have a certain color and it just doesn't turn out that way.

I once grew a seed which was the 846 Calai, selfed three times. The fruit was white!

11/15/2010 6:41:21 PM

Cincinnati,OH

The 603 Muller is a good example of a selfed seed that expresses a desirable trait.

11/16/2010 11:16:40 AM

Anchorage, Alaska

Thank you all for the insights into my selfing question.

11/16/2010 12:44:49 PM

Bemidji Minnesota

I do think that with enough generations of selfing color and shape would get more predictable.

It can take more than 3 generations sometimes. I know some plants it can take as much 10 generations before seeds are truly predictable.

Generally it only takes 3, but then again, as Cliff found out, a 846 Calai x self x 3 has gone white! Now that may be the example of the odd one out, OR that a recessive white gene was found in the selfing process met up to another recessive white gene to do that.

Part of the selfing process would involved getting weeding out the ones that turn out wrong too.

I know that with Tomatoes, its is call dehybridization, often a dozen plants are grown from seeds of the last F generation, and only the seeds of those that turn out right are kept to grow out the next year. Each generation a higher% turn out like the desired one, and less turn out wrong. Eventually you get seeds that always throw true, and it is often called an Heirloom, or Open Pollinated variety (maters are self breeders by nature, with only a very small % of natural crossing).

11/23/2010 12:39:40 PM

Bemidji Minnesota

The reason I think that color and shape are genetic is based on all the other types of C.Maxima. There are not specific genes different with AG's and other Maximas. All the difference we see are in the Alleles attached to genes that control gene expression.

Other than that, a Hubbard Squash, a Buttercup, Banana squash, and Kabocha Squash ALL have the same genes as the Atlantic Giant. They have different Alleles controlling the expression of such genes, but all the genes themselves are interchangeable, and can produce fertile offspring.

There ARE some big differences with Atlantic Giants and the other Maxima squash, besides the obvious size differences.

One that stands out to me is the unpredictable shape and color of the Atlantic Giants. I do think that has to do with the amount of out crossing the Atlantic Giants get. We cross lots and lots of pumpkins that have very different morphology. The result is lots and lots of different shapes produced by the same vines. Yes growers can get long and flat, and high and round on the same vine, even if positioning the fruit the exact same ways! I realize the way a fruit is positioned can effect its growth, as physics has a different outcome on 50 pound fruit vs 500+, but when positioned the same way we still get drastically different shapes at each weigh off every year.

I do know however that this is not the case with the other Maxima varieties. Hubbards turn out like Hubbards, and Kabocha turn out like Kabocha, and Banana Squash still look like Banana Squash, with only very rare exceptions.

11/23/2010 12:58:23 PM

Bemidji Minnesota

Well, all of those, so far as I know are a lot more inbred than the constant out crossing done to AG's. I do think that with enough generations of selfing some lines of AG's could become very predictable in color and shape too.

Now, due to the generations used for selfing in getting said predictable round shape, medium ribbing, and good orange color, these selfed lines would fall behind the weights of the unpredictably shaped front running lines that are crossed over and over again for more weight.

Its not that the continuously selfed ones are getting smaller, they would just be stagnant as nothing new is added. So if it had a top weight for an orange and heavy round pumpkin was say 1200 pounds for example, that would be the upper limit, while in 10 years the upper limit of unpredictably shaped monsters would be over 2000 pounds.

But there could still be a use to the selfed lines and that is we KNOW which traits they will give when crossed into a more recent line.

In other words, if you have an F1 with nice orange color, it may easily be carrying a gene for white color, and there is a 50% chance you will be putting the white color gene into your new “color cross”.

If it was a nice round and orange F7 pumpkin, then there is a much better chance that its color is on both sides of its parentage (as the wrong ones should have been weeded out by now) and that you have closer to 100% chance at putting the orange gene into your color cross in the new F1 mixture.

11/23/2010 1:02:33 PM