I have been wondering for a while now about whether it might be useful to take a bit of a look back over the results of some of the assisted germination strategies that I have seen here over the years to see how useful they have been and how successful they have been in the long term. The assisted germination methods I have been thinking about include embryo extraction and things like stratification media additives (such as the 10mM Calcium nitrate solutions).
I have only tried the embryo extraction method and have done it quite a few times now. In the end I have only kept one seedling long term that has proven useful. The others have all been discarded for poor health and vigour or have died very shortly after extraction for no apparent reason. So I began wondering what kind of success others are having and if anyone can report on how useful these seedlings have been to the advancement of their breeding programs. I don’t perform embyro extractions any more because I have decided that my selection needs to start from germination and if they can’t germinate on their own then they probably weren’t meant to. The only successful and really useful seedling that I have kept, that is incredibly strong and healthy, is a Rosa longicuspis var. sinowilsonii x ‘Violette’ seedling ('SV-2011-RLSxV' Rose). It is an outstanding seedling but, whilst appearing fertile, is proving very hard to work with because its own seeds seem to be impossible to germinate even though it makes loads of them. I am now using it as pollen only in hybrid hulthemia crosses to try and beef up this particular line of hybrids. I should really mention that the only seeds that I have attempted embryo extraction on are ones that have traditionally come from poor-to-no germination lines and have not done it on seeds that I don’t usually have trouble germinating or getting to adulthood. I feel this is a very important variable to mention.
Has anyone else noted any drop in the overall vigour of their lines involving such assisted germinations?
Thanks for the observations Simon. I expect your are correct for many instances of embryo extraction. I only know of one acknowledged seedling that made it to market after being extracted. That was back in the 1940s. However, von Abrams and Hand found good luck getting growth from extracted embryos and used it as a test for viability when they had seeds that didn’t germinate under their normal conditions. they never published survival data on those, only germinability in lab culture conditions. You can consider that you are doing a C-section for seeds. How does that square with natural selection is a hard one to answer. The cattle breeders probably have the best data on assisted reproduction. I expect it’s not all positive.
I personally don’t view calcium nitrate, or kar1, or other additives of things likely to be found in soils as “assisted” any more than I view stratification under cold conditions as an artificial assist. Both nitrate and kar1 are overcoming dormancy that was likely induced by post-harvest treatment. If scarification was beneficial, I’d consider that too. After all, any legumes need to be roughed up to germinate. Often that is by passing through the digestive system of some creature, a fairly natural process given that they may be surrounded by very sweet attractive pod material.
I’ve had close to 90% germination of R canina using nitrate. I’ve not kept the seedlings because they are simply too abundant to manage by hundreds. In direct comparisons with CV that I intend to keep I’ve never noticed that the ones induced by nitrate are weaker than those that aren’t. And for some the nitrate treatment is the only way I’ve managed to get more than 1-2% germination, so there’s no direct way to compare survival statistics.
Some day I hope to write up the whole experience with nitrate, when I get to retirement.
Keep good notes and generate some statistics for us. You are raising good points.
Merit of assisted germinations…good point to explore Simon and great to see you active on the forum again.
Depending on the hybridizers’ goals, different responses may be presented. My limited experience using embryo extraction can be summarized by this photo (Alba Semi Plena X Souvenir d’Alphonse LaVallee):
Is it possible to attain the goal of producing a new/unique cultivar from a seed parent that has major germination issues?..Certainly.
Will these seedlings attain the goal of great health and be worth saving?..Perhaps…but often not.
My experience…embryo extraction can yield results… but for the hybridizer germinating huge numbers of seeds to target a specific trait logistics become an issue. Health and vigor of seedlings derived from the assisted germination technique of embryo extraction may be excellent…enough so for me to continue to use the procedure.
Watching lots of videos and reading articles on the art of embryo extraction. I’ve been successful in removing embryos
from large seeds like “Olympiad”. But having difficulty working with small seeds like R. Arkansana.
Assuming that you are using fingernail clippers you will benefit from sharpening their blades before you begin - right out of the package.
For this purpose I use a Dremel sanding disk with the disk mounted in reverse, abrasive facing the tool. You can stiffen the disk by gluing it to a thin bit of cardboard from, say, a cereal box.
The reason to mount the disk in reverse is to be able to sand the inside of the blades rather than the face side. The principles of knife sharpening apply, the finer the grit the sharper the tool. I use 400 and 600 grit silicon carbide abrasive sheets to make my own disks.
Take care to grind at a relatively low rotary speed, use a light, even touch as the blades of the tool need to meet in parallel to be effective.
Repeat as needed. I get maybe 100 - 200 seeds out of a clipper before I touch it up again and, while it varies a lot, I only get maybe three or four touchups out of a clipper before I toss it.
Although it should be intuitive, keep the blades free of debris between bites - I use the fingernail on my thumb to swipe the blades.