Re: Hybrid Vigor

Brian, all:

I think you summed up the math part of what I was trying to say... 15, or maybe
12 for our purposes, seeds from the same GOOD seed stock, planted under
nearly identical conditions and self-ed or sibbed.... Then keep only those seeds
from one resulting fruit that has the characteristic you want (weight)... This could
lead to a superior seed stock, especially if it were repeated for several years.

What seed to start with? Any good seed stock that has characteristics you like
would do. But you'd have to like it... because you'd be stuck with it for a long time.

We could get too technical on the numbers... (OK, I'm too lazy or busy to do more
math! ;-) ) But I would apply some fuzzy logic here and say:

Fifteen plants would make a superb experiment. I think Brian's numbers show that.
Although, I think all or most of the seeds, not just 30%, would be applicable on a
good seed stock.

Twelve plants would probably make a good experiment.

OK, if I get bored tonight (doubtful) I may try to figure out some numbers. ;-) I'm
getting rusty on this stuff.

Me? I have a wife and 5 kids and a full-time job, so I have no time for pumpkins.
But I make time anyway and try to grow 3 or 4 plants. ha ha

Regards, Cliff





From: Brian Reid <brianreid@charter.net>
Reply-To: pumpkins@hort.net
To: pumpkins@hort.net
Subject: Re: Hybrid Vigor
Date: Mon, 22 Dec 2003 14:38:05 -0800

Cliff,

The math is the easy part. When all the talk about genetics, lineage, crossing
back, hybrid vigor, etc. starts I'm at a loss. I have no clue when it comes to
seed genetics, and I've been unable to find any site out there that helps me with
the genetics part of it. Thank you guys for posting on here and giving me a lesson
on the basics....and the not so basic. Keep up the great discussion and I'll
continue to try and take it all in.

Happy Holidays

Brian

clarion wrote:

> Brian and Cliff;
>
> Great postings from both of you guys! You guys do the math and just tell us
> dummies what the hell will work to do a properly controlled experiment and get
> accurate results!
>
> Marc
>
> -----------------------------------------------------------------------------
> ---
>
> 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
>
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