I have a Carefree Beauty x J5 seed that germinated without cold stratification. When I looked at the two halves of the seed coat I noticed another embryo inside. Does this happen very often and what can I expect from the second embryo? Is this from a separate fertilization or is this an unfertilized egg that developed? Could the embryo have divided to form identical twins? I’m just wondering if anyone has seen this before and if the seedlings differed in any way.
Thanks Paul
Not that I have ever seen this but there are several interesting discussions on this topic. See link http://www.rosehybridizers.org/forum/message.php?topid=10055#10064
Link: www.rosehybridizers.org/forum/message.php?topid=10055#10064
Thanks Jackie,
That was very helpful. Now that I read that post I do remember reading it before.
I got out my magnifying glass and the best that I could tell is that the second embryo has its own papery covering so its probably a genetically distinct embryo. Now I just have to wait and see if the second one germinates.
Paul
Hi Don,
It may be more common than we realize especially if the second embryo doesn’t develop. Also in the past when I saw two seedlings sprouting right next to each other I assumed that I accidentally planted two seeds in that spot and in those cases that may have been true, but it
Hi Paul,
That’s great you had twin embryos. It seems like the ones with two embryos within a single testa, covering, are much more rare and those are the ones that we are more likely to find haploids.
I’m surprised to have found a number of haploids over the years not only in twin embryos, but also just careful observation as well of seedlings with one embryo per seed. Over the years Rise ‘n’ Shine and ‘Dorcas’ have produced 3 and two, respectively. Unfortunately, for the most part they are relatively weak and most aren’t fertile. That is the challenge with haploids in general and has been reported in potatoes and other crops as well. Finding the relatively rare ones that have enough vigor and fertility to be able to cross is the hope. One of the haploids were just found because the seedling was a repeat bloomer and the other parent was a one time bloomer homozygous for one time bloom. Chromosome counts confirmed it was diploid. Even in a cross with repeat bloomers there was a seedling that seemed more petite in size and didn’t have any characteristics of the male parent and was found to be diploid as well.
I think if we are looking for traits that are consistent with haploids among our seedlings we will eventually find some. Having the tools/skills to confirm ploidy will of course help in the process. I think many are overlooked because they aren’t the goal and because they tend to be a little weaker and are just weeded out. I think haploids of modern tetraploids can be great stepping stones to cross with diploid species and classes of roses to better understant inheritance through more manageable segregation and to help overcome some fertility limitations due to ploidy. It sounds like the French group that worked with haploids made some great seedling populations of their haploid hybrid teas and Rosa wichurana. It sounds like the research component is closed, but Meilland still has and can work with the germplasm.
Hopefully I’ll eventually get some haploids with useful fertility to pursue this line of work. I can still try crosses irregardless of ploidy of course. I’ll keep playing with the haploids I have and see what is possible.
Sincerely,
David
Hi David,
I tried taking a picture of the second embryo but my camera won
Hi Paul,
How is the embryo
Hi Don,
That
At first the vocabulary had me a little confused. I’m more used to yeast genetics where haploids are also monoploids. But for tetraploids of roses the haploids ought to be equivalent of diploids. So there’s no physiological reason why at least some of the offspring should not be healthy and vigorous. That’s just how maize inbreds can be these days (very vigorous) unlike 100 years ago where there was incredible heterosis arising from crossing two rather puny inbreds. But with all of the deleterious genes exposed in haploidization of the tetraploid its likely that most of the offspring will be less healthy than the tetraploid parent. It probably had heterosis effects if it was derived from crosses between different genetic bases. Certainly for Carefree Beauty with its complex parentage, halving the chromosome number will take away some desirable traits, while seemingly enriching others. Somehow you need to test a bunch of these to see. Too bad they are so rare.
David wrote: “It sounds like the French group that worked with haploids made some great seedling populations of their haploid hybrid teas and Rosa wichurana.”
I saw the “diplohaploids” derived from florist HTs. (haploids from tetraploids are diploids). Fertility was varied with some not bad. Very reduced plant size and sturdiness: somehow intermediate between thinner stemed, leafed and petaled diploid Slater’s like chinas or laxer patios.
As all these were greenhouse grown, desease resistance is unknown to me. The only fact I was informed is that non expected ploidies were rather frequent in progenies from these “diplohaploids” crossed with diploid species . With the expected diploids were triploids, tetraploids, pentaploids… if I remember well even a quite freaky octoploid.
The root tip on the second embryo has started to emerge. Now it’s wait and see if it grows into a viable seedling.
Paul,
Here is a double embryo I came across yesterday while practicing my embryo excision technique.
Here they are split apart. After getting the testae off, one of them appeared to be non-viable (dark and opaque looking rather than pearlescent white) but the other seems to be ok. This was from Yellow Submarine, OP. I had another from Julia Child OP as well, but both embryos were non-viable.
Those ae great pictures Don. Are you going to try to germinate both embryos anyway? I would.
The second embryo did germinate for me , but I accedently broke the root tip off of it when I moved it because it was stuck to the paper towel. I planted it in soil anyway with the hopes that it’ll continue to grow. It hasn’t emerged from the soil yet.
Yes, I am putting both embryos through the germination protocol but my experience is so far that if it looks dead, it is dead.
I’m still working out the best practice for germination. Tricky business, but not rocket science.