Species hybrids chromosome counts prediction

About the words below; as I did follow the work and often looked at the plants the “french group” raised as well as from my species crosses;

I can agree and add some precisions that one may find interesting.

There were found many unexpected seedling/gametes ploidy such as a pentaploid seedling from a diploid species crossed with a diploid they raised from tetraploid cutroses (dihaploid).

As well as many unexpected phenotypes (plant habit) i.e. a recurent seedling from the species wichuraiana as mother.

One can say: When the hybridizer introduces species (or other highly dissimilar roses) into a breeding line…

…chromosome count is not allways predictable, nor is phenotype.

Paul Barden and David Zlesak wrote in

“Conducting Chromosome Counts on the Bracteata hybrids”

When the hybridizer introduces species (or other highly dissimilar roses) into a breeding line, then the outcome is less predictable than one might think. In the case of ‘Muriel’, we have a tetraploid that is producing gametes with varied chromosome counts (almost certainly a mix of at least 1x and 2x), resulting in offspring whose chromosome count is not predictable, regardless of the chromosome count of the other parent.

Dear Rutten Pierre,

If I understand your message correctly, you saw the haploids (diploids from tetraploids) of the French group. Wow, what is your impression of them and the variability you observed among them? Do they appear somewhat like the old diploid tea roses in growth habit?


I am living only a few km away of the greenhouse “the french group used”. And for about thirteen years I was quite interested at their work as you would isn’t it? This group has been disolved by administrative decision. Some members are still here with other tasks others gone.

Yes I saw the “dihaploids” as they were christened.

They are no more here actually but probably in Angers INRA Station. A few dozens plants quite varied: some ugly (more than the usual seedlings) others well balanced. Size is about Patio with more numerous thinner stems, some quite vigourous, thinner petals, some quite China like comparable to Slaters Crimson unselected seedlings, some more modern looking. No desease resistance as they were from greenhouse cut-rose vars. Not very female fertile but pollen of some was quite effective.

A few species hybrids were raised from this pollen. Some diploids as expected but a lot of unexpected ploidies: triploids, tetraploids and higher polyploids with thick stunted growth.