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RE: TB Pink Carrier Immortality

Pedigrees are very usefull for finding out what a plant carries but can't tell you what it doesn't carry. A gene can be hidden for many generations before showing itself. Thus because pink parents/grandparents are not present, it doesn't mean it isn't there. Thus the absence of pink in parentage  doesn't mean it's not there, while pink paarents deffinately says it is. Abssence of the positive is not the negative. This only applies to the recessive genes as the Dominant genes will show itself with only one gene (unless another gene supress its expression, this cravat is only for the very knowledgable genetic people as otherwise someone else will shirley point this out).
The only positive test is a cross to an an all recessive plant (eg; cross Immortality to a pink). This will quickly tell you if Immortality carries two pink genes as in this case 1/4 children will be pink (perhaps white with pink or red beard but considered pink). If 1 out of about 100 is pink then it obviously carries just one pink gene (for more details read World of Iris  section on tetraploid genetics). If no pink off spring then this does not rule out carring one pink gene. What we have to do in this case is cross a number of the F1 to another pink and count pink offspring. If the F2 is all the same with 1/4 pink  then there is no pink gene in test plant (Immortality in this case). If 1/2 of test crosses (F2)have  1/4 and the  other half have 1/2 then test plant has one pink gene.

If you find one or two plants registered  as having test plant as a parent, this does not mean that the test plant for sure has two pink genes (although is the most probable situation). To be certain we would need to know ratios in the cross producing the child. If about 1 in 100, then it would be 1 gene, and if about 1/4 then it would be two genes.

Thus when I  stated that Immortality was a carrier but I wasn't sure if it was one or two, it was for exactly this reason. I don't know ratio of pink offspring but was aware tha Immortality has produced pink children.

Also one must consider errors in parentage either accidental (accedents do happen, pets move plants, seeds get dropped etc, etc) or deliberate, where people falsify records deliberatly to keep others from working their discovery. Ask Keith Keppel re this, he has some good stories, but keeps mum re identifying data. 

Chuck Chapman, Guelph, Ontario, Canada. Zone 4/5

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