I’m hoping to start my first planned crosses this season making the transition from OP seeds to planned crosses. So in my reading I’m up to the learning about timing it all. I was wondering whether there is any difference between pollen maturation and stigma receptivity in roses (in general - or is it too variable from species/variety to sp./var. to be able to generalise?)? Does pollen ripen first then once released does the stigma become receptive to reduce the chances of self-pollination or do they mature simultaneously?
I think you are right when you say it is variable. In general for most modern roses my suspicion is that they mature pretty close to the same time. As the bloom matures and ages the filaments continue to elongate and curl over to help ensure some self pollen gets on the stigmas. The gametophytic SI system over time may break down a little and then allow some self fertilization in some clones at this point. Rugosas have pollen mature and release often before the flowers open and stigmas mature, but a strong SI system discourages self fertilization.
I tend to emasculate and pollinate at once because of logistics. If you come back and repollinate again a day or so later you can get a substantial increase in seed set. There is a nice article on that which has been highlighted on the forum and newsletter. The Dutch researchers repollinated once, twice… and found that there was continued gain in seed set from repollination, but the greatest jump was from just one pollination to two and for us that may be the most practical as breeders for our time and effort.
Regarding how offen to pollinate, see:
If one pollinates multiple times I assume that it is to ensure a greater proortion of successful fertilisations yes? That would mean a greater number of seeds produced and a greater necessary distribution of resources within the plant. When there is a higher number of seeds produced does this affect the overall ‘quality’ of the seeds? Are we better to have a smaller number of really good seeds than a lot of inferior quality seeds? Is there any correlation between seed quality and seedling quality and/or vigour? Is it better to distribute more pollen over more flowers (pollen and flowers permitting of course) than trying to get more seeds into the one hip? I know with some of my open pollinated hips from last season I had so many seeds in the one hip that the hip seemed to burst at the top and overflow and they seemed to be good seeds but competition for space alone caused them to be a little deformed.
Interresting graph Henry, I didn’t know this and I’m going to try this next season.
“I know with some of my open pollinated hips from last season I had so many seeds in the one hip that the hip seemed to burst at the top and overflow and they seemed to be good seeds but competition for space alone caused them to be a little deformed.”
I have this with my Nostalgie x Golden Celebration and Nostalgie x Golf at the moment. 3 Seeds are on top of the hip now. Those seeds which are outside, do they make it to useble seeds?
That is a great question about seed viability and number per hip. I think that an experiment one can do would be to make various pollinations all on one day on the same cultivar with the same pollen parent and somehow try to get variable seeds per hip. Perhaps the repeated pollination scheme or cutting off some of the stigmas, or different amounts of pollen being used at one pollination could all do it. Then, follow how long it takes to have a hip get to some key point of color and harvest and count the seeds. The seeds can be followed for their germination rate as you suggested.
From piecing together different parts of various experiments in the literature and just observation I see a trend that the hips more full of seeds ripen earlier. I think hips with many embryos and their hormonal signaling makes the hip a particularly strong draw or sink for nutrients. This allows such seeds to develop more quickly and the hip to change color and seeds to ripen more quickly. Perhaps that translates into stronger seeds with better germination, even though they were crowded.
What do others think?
Simon, for me the greater question has been how to maximize efficiency. I use very little pollen and only pollinate once. I think that local climatic conditions may contribute to success or failure, so everyone’s experience can be different and may or may not apply to you. As for number of seeds per hip - I don’t think that it is so much dependent upon the amount of pollen applied as it is to whether the pollination is done early rather than later in the season. I get the most seeds per hip on the early pollinations. These also tend to have higher germination rates. As mentioned above, there is a great deal of variability in all of this with roses. Just when you think you have figured it out or seen a pattern, something totally different happens than what was expected. But, we all keep trying to learn a little bit more!
It’s all very interesting. I think I’ll have a play with designing some experiments and see how I go (sounds like a good excuse to tell my wife that I need statistically significant numbers of roses LOL).
I used a lot pollen for a single hip this year and it seems to be that I have not more succes with it. New Dawn sets a lot hips but I expect the same amouth of seeds per fruit. Last year I had an average of 4 seeds and the size of the hips are the same.
28 May I crossed Treasure Trove and the hips are orange colored. The New Dawn hips are getting red but the hips wich I pollinated in mid june are still green.
Next year I’ll try to use a little less pollen.
I tend to agree with Jim Sproul rewgarding pollen though I’m considerably further north so every part of the season is weeks later than he sees. When I have lots of pollen, like with Carefree Sunshine, I will dump on a lot. But I’ve not seen any big difference between emasculating in morning and pollinating right away vs waiting 'til evening. I don’t like to let dew collect overnight so I rarely make an intentional wait of a day. But if I see flowers that I emasculated the previous day and they don’t have a tag indicating they’ve been pollinated I go ahead and pollinate again. For sure with some CVs the stigma is more receptive-seeming the 2nd day. It is sticky then, whereas on the first day it is not. But I think that enough of the pollen survives in place that you can put it on right at emasculation time and it will still give a good seed crop. In cabbage type plants, you can successfully pollinate before the flower is ready to open. In fact that is done to overcome self-incompatability in those species, which only develops as the seed matures. For all I know the same may be true in some roses.
The graph Henry showed is for classic HT for under glass where I think the rate of flower maturation is a lot slower than with species and near species that have flowers only lasting 1-3 days. The benefit of multiple pollinations seems marginal, if female flowers are available in abundance, and the way the experiment was done we don’t know if the first day of waiting was necessary or just a habit of the breeders.
This year I got about 90% takes on Carefree Beauty with Carefree Sunshine as pollen parent. At the same time with the same lot of pollen the rate was maybe 1/3 on New Dawn. New Dawn always gives poor hip set for me. And the seed/hip is always small, scarcely ever more than 4. I presume this is because there simply aren’t many suitable ova from this triploid. It’s not likely to be limited by pollen amount. Many Cv give < 10% takes on New Dawn in my experience and I’ve tried a lot of different HT and minis (mostly yellow). Those same CV on Carefree Beauty have a relatively high take, and commonly a decent # seeds, even with very stingy pollination. I’ll go back and make a table of what data I have.
For me the bigger problem is that I’ve never gotten a fertile seedling from New Dawn, as the seed parent, so that whatever I get is a dead end. If it is interesting for itself that’s great, otherwise, boring. Most are pale, between yellow and pink but pale. My best result was one of my first, Silver Sunrise (ND x Rise N Shine), still going strong after more than 20 years at the university rose garden. This year we planted some out at a community gardens place in an exposed place with no attention (except maybe water, I was’nt caring for them so I don’t know)and they bloomed right through a month of 100 degree days.
The reason I asked this was based on work I did as a student on banksia microstructures that showed there was an interaction between stigma microstructures and some form of recognition strategy that allows banksia to select against self pollen in preference to cross pollen. Delayed maturation of the stigma was one strategy used to ensure that self pollen was less likely to compete with cross pollen (we were trying to account for lower than normal seed set in natural populations) and I was wondering if roses displayed similar tendencies?
I understand the first article that Henry linked to but will have to wait till the kids go to bed to undestand the 2nd one properly (the killed pollen has me thrown a bit???). It makes sense that some pollen would be more vigorous once germinated than others and that seedlings resulting from more vigorous pollen may inherit some of this vigour - but - our gardens are hardly going to be resource poor…
Another thing I have been wondering about is whether roses are self fertile or self sterile? So if you have OP hips are they likely to have been self-pollinated because they are self fertile or from another source due to self-sterility issues. I have a feeling that it is probably a variable thing like the pollination timing thing and that this probably relates back to ploidy issues.
Regarding: “Another thing I have been wondering about is whether roses are self fertile or self sterile?”
Regarding pollen load, see:
I wonder if microwave radiation could be used in place of gamma irradiation to treat the mentor pollen.
Another paper by Visser and Marcucci:
Two more Visser et. al. papers:
Simon, in my experience, good tetraploid rose seed parents (those that easily set hips), are highly self compatible. Open pollinated hips on them therefore usually are the result of self pollination. This would be consistent with some of Henry’s references above.
I have had several converations with Mr. Ralph Moore on this subject and he has said that he has rarely seen an open pollinated seedling have characteristics that would suggest that it was anything other than the parent “selfed”. I have grown thousands of open pollinated seedlings and my experience is in complete agreement with Mr. Moore’s observations.