How does one suppose ‘Emily Gray’ ended up a triploid? See: 'Emily Gray' Rose
I’m not sure about how this rose ended up a triploid, but triploidy is common. We can get triploids from crosses of two tetraploids, a triploid and a tetraploid, two triploids, even two diploids. With the vast diversity in the background of our modern roses, chromosome pairing and segregation during meiosis can be quite variable and lead to surprises. Here is a paper where I learned the variable ploidy that one can get from crosses between and even within different ploidy levels http://www.globalsciencebooks.info/JournalsSup/images/0906/FOB_3(SI1)53-70o.pdf
Interestingly, there are a lot of triploids out there among some of our common standardly grown roses- Tropicana, John F Kennedy, Incognito, etc.
So… from two diploids, how does this happen? Is it an unreduced gamete from one diploid parent matching up with a reduced gamete from the other diploid parent? This is what (supposedly) happened to ‘Max Graf’ make ‘Kordesii’ (pollinated by tetraploid 2n pollen), isn’t it, also from wichurana?
SimonV,
I found this item just yesterday that would explain the chromosome number:
USDA Inventory of seeds and plants imported (May 1922)
From Cheshunt, Hertford, England. Plants purchased from Paul & Sons. Received May 9, 1918. Quoted notes by Dr. Walter Van Fleet.
- ROSA sp. Rosaceae. Rose.
“Mrs. Emily Gray. Jersey Beauty X Rosa pernetiana. Jersey Beauty has for parents Rosa wichuraiana and Perle de Jardines, the latter a yellow-flowered form of R. odorata. Mrs. Emily Gray is said to be the best yellow-flowered form of the wichuraiana type that has been developed. Desirable for breeding.”
Karl
Thanks, Karl. That would explain it! It would certainly explain how the form shown here originated: 'Emily Gray' Rose Photo . I have ‘Jersey Beauty’ on order this winter and am hoping to put it with good strong diploids.