Re: Hybrid Vigor
I'm a newbie and don't know a lot about seed genetics but I do know a bit about
statistics. You are pretty close with your estimation on the number of seeds you
need to grow Cliff. Obviously, we're making a couple of assumptions when saying
you only need to grow 15 seeds to obtain a 95 percent confidence interval. The
first and biggest assumption is the percentage of seeds in the pumpkin that
possess the traits you're after. Without acutally growing every last seed, it's
a shot in the dark. Half of the seeds in the pumpkin could contain the traits
you're after or as little as 10 percent of the seeds could contain the trait you
want. This assumption greatly effects the number of seeds you need to plant in
order to get an accurate representation of all the seeds. The second assumption
is that the data is accurately represented by a normal curve. I ran the numbers
and used a probability of 0.3 or 30%....meaning that we're assuming 30 percent
of the seeds in the pumpkin will exhibit the trait you're after. I'd say that's
a pretty fair and conservative estimate. The higher the probability, the less
seeds you have to grow.
To figure out the number of seeds you need to plant in order to establish a 95
percent confidence interval, you have to first find the standard deviation.
Sorry if no one wants to see how the numbers work out, but I think it's
important.
std. dev. = [np(1-p)]^1/2 where n = the total number of seeds and p is the
percentage of seeds that posses the trait you want.
= [(300)(0.3)(1-0.3)]^1/2 = 7.94
Using the std. dev. of all the seeds we just found you can calculate the std
dev. for the based on only 15 samples. This calculation will give us a number
that represents how confident we are that the 15 seeds we planted accurately
represent the 300 seeds in the pumpkin.
For 15 seeds.....
std. dev. for the sample = (std. dev. of the 300 seeds)/(n^1/2)
= 7.94/(15^1/2) = 2.05
So, using 15 seeds we've covered a little more than 2 standard deviations. This
means that by planting only 15 seeds of the 300, we're representing the 300
seeds with an accuracy of 95 percent. By planting only 15 seeds, you're still
getting a fairly accurate representation of all the seeds (95% accuracy to be
exact) but you're doing a whole lot less work compared to planting every last
seed in the pumpkin.
Brian
Cliff Warren wrote:
> >Your defiantly have the correct idea in mind, basically. The problem in
> >actually doing this kind of breeding lies in the vast number of seeds each
> >plant produces. Who is actually going to grow all 300 and something seeds,
> >take time to watch and chart the very best plants and pollinate every
> >plant,
> >them do the same thing for several seasons? This would require a commercial
> >sized growing plot, excessive amounts of time, and a lot of documented
> >research.
>
> I was just about to jump in here, and your post made me do it.... you don't
> need
> to plant all 300, but just a number derived statistically that would get you
> a, say
> "95% confidence level that one of the seeds is in the top 10%", sort of
> thing.
> These numbers are big but not huge... for example, for a pumpkin that had
> 500
> seeds, this number may be in the range of 12 to 15. That is, plant 12 to 15
> seeds from the same highly regarded pumpkin, grow them in identical
> conditions,
> and choose the best of what results. Repeat the process.
>
> I could do the mathematics (consult my Statistics textbook) but this sort of
> number
> is really in the ballpark. If you take 12 to 15 seeds from any one pumpkin,
> one of
> them is very likely (by a measureable amount) to be in high side of the
> "bell curve"
> of the potential of all the seeds in that pumpkin. Note that 3 seeds won't
> cut it, and
> one seed is really a random "crap shoot", and there is really nothing grown
> under
> identical conditions to compare to...
>
> If we had growers that had the time and space and inclination to plant so
> many
> seeds on one sole seed stock, I think we could really advance the genetics.
> (Not that we're not already doing that!)
>
> If you read the story of Helmut Laemelle on AGGC, how he just selected seeds
> from
> his largest pumpkin each year, and continued planting those, you can see
> that
> perhaps he was using this same process. (His seed was then crossed to become
> the
> 567.5 Mombert...)
>
> Regards, Cliff
>
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