Re: Parentages

From: Harold Eddleman
See my comment at the very bottom; a problem I am struggling with.

pumpkins@mallorn.com wrote:
> 
> > I fully agree with you on this, and in light of discussions with
> > Harold, I think it might be a good idea to carefully identify 
> > "self" or "sib".  eg. 123 Eaton 1998 x self is not the same as 
> > 123 Eaton 1998 x 123 Eaton 1998.
> >
> >Till next time...
> >*******************************************************************
> >Rock - I agree with that and perhaps we can encourage others to do the same.
> 
> This means pollination could be:
>  open----by mother nature
>  cross---by hand-from plant of a different mother
>  self----by hand-from same plant
>  sib-----by hand-from different plant with same mother
> 
> The only change would be as follows:
> 
>         This----700 Rivard 99--600 Rivard 98 x 600 Rivard 98(self)
> 
>    Or This-----------------------------------x 600 Rivard 98(sib)
> 
> I'm not sure that the terms are all botanically correct but I think it is
> OK and would be an improvement and leaves little room for error.
> 
> How does this explanation look to you?
> 
From: Harold Eddleman 
  We can add testcross (tc) to Rock's list. In a testcross we mate an
unknown with homozygous recessive as a cross to test whether the unknown
has the recessive gene. Testcrosses can be very useful also when
checking linkages (assigning gene to chromosome or location on the
chromosome). We are not that far in AG genetics, but Keel just sent me
some testcross data on seed color which he discovered in his records.    
  Here is a complication. Suppose a vine has 2 or more fruits. I think I
have heard of vines that had more than 3 fruits and each was a few
hundred pounds weight. How do we name those pumpkins?
  Keep in mind that the female contribution to all four fruits is
identical. Therefore, if you selfed all 4 fruits, the seeds from all the
fruits are similar and there is no reason not to put them in a single
jar. In practice, I might cross the first female flower, self the second
flower, and sib or testcross the 3rd and 4th flowers. I guess a
contestant wants only one fruit per plant, my remarks above are for your
seed (or research) nursery.
  While all siblings are, on average, somewhat identical, they can
differ greatly in allelic content. Sibs are not identical twins.
Siblings differ greatly in production potential. Therefore, I have
always identified the the sib that furnished the pollen and a seed bag
might have this label: 1998-34Db sib A. That decodes as follows. Fruit
was grown in 1998; second ear on 4th plant in row 34; pollen was from a
sib which was the first plant in the row. [All the seeds planted in a
row came from one fruit].
  My point is: We may speed up our progress to large fruits if we
understand the parentage better. It may make a difference if a future
breeder can look back and know that two  WWW Dill 1991 are different
seeds. A human can figure that out as they were planted by different 
breeders, but to a computer they are identical. They are the same string
of characters.
  I am reading Lerner's "Genetic Homeostasis" (1954). He gave lots of
data and in all instances inbred lines had greater varibility than the
hybrid created by crossing them. One lesson from this is that if you are
inbreeding by selfing and sibbing to get a line pure for important
traits, you have to expect pumpkin weights to vary alarmingly. In his
examples they had sibbed (brother x sister) for 10 to 60 generations.
They used mice, chickens, fruit flies, but plant breeders had not
recorded variability--seems they blamed it on growing conditions.  

 In my corn work I labeled the top ear A and the next was B, C, D (rare
plants did produce 4 ears having seeds). If you ask me about
1971-100Db,  I can get my 1971 notebook turn to the page for row 100 and
read lots of nice details, from the page header, about the ear planted
(including its identification), go down to the 4th plant (D) and tell
you its description, and under b tell you about the second ear (the
pollen used, size of ear, color of seed, etc).
   
-- 
Harold Eddleman Ph.D. Microbiologist.       i*@disknet.com 
Location: Palmyra IN USA; 36 kilometers west of Louisville, Kentucky
http://www.disknet.com/indiana_biolab/pk.htm
genetics@onelist.com <= currently devoted to AG genetics. Definitions,
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