My R. setigera var. serena set tons of OP hips with seeds in them. I was very curious to see what nearby rose had pollinated them, since most of the other species roses were done blooming before R. setigera started. The interesting thing is that out of hundreds upon hundreds of OP seeds exactly zero germinated while a far smaller quantity of seeds from controlled crosses yielded a handful of seedlings.
There are contradictory reports about the fertility of the pollen from “female” specimens.
Kevan, et al.(1990), “…pollen from female plants appears somewhat collapsed and does not germinate.”
http://bulbnrose.x10.mx/Roses/breeding/KevanSetigera1990.html
Cole (1917), “R. setigera shows a large percentage of microsporic degeneracy.”
http://bulbnrose.x10.mx/Roses/breeding/Cole/Cole_pollen.html
Shepherd (1954), “As much as 80 per cent of the pollen of the seed-bearing plants may be sterile”.
http://bulbnrose.x10.mx/Roses/breeding/ShepherdSetigera1939.html
Floriculture and Ornamental Biotechnology (2009)
Review of the Breeding Systems of Wild Roses (Rosa spp.)
Victoria J. MacPhail, Peter G. Kevan
http://www.globalsciencebooks.info/Online/GSBOnline/images/0906/FOB_3(SI1)/FOB_3(SI1)1-13o.pdf
This one goes into (too?) much detail about the various types of self- and cross-pollination. One example is geitonogamy, which means moving pollen from one flower to another on the same plant. This is a form of self-pollination, but Darwin reported that the results differed from pollinating a flower with its own pollen. And somewhere in my notes I have Michurin’s comment that moving pollen from one side of an apple tree to another gave seedlings with more vigor than pollinating within the same cluster.
I would guess that mating two specimens (form different sources) of the same cultivar would give better offspring than simple self-pollination. E.g., pollen from ‘Crimson Glory’ growing in Canada, transferred to a ‘Crimson Glory’ growing in Ohio, should give better offspring than self-pollinating either of the parents. That would be wide geitonogamy.
On another track, effectiveness of various sexual systems can vary with age as well as environment. Wood (1932) reported that walnuts (Juglans spp.) are dichogamous to varying degrees. “Dichogamy varies with the age of the tree. In the varieties studied it is more complete in young than in old trees. This apparently accounts for the fact that some varieties (for example the Franquette) do not bear well until the trees are fairly old.”
http://bulbnrose.x10.mx/Heredity/WoodWalnutDichogamy1932.html
In this case, the dichogamy becomes less effective with age. I have read of cases where a sexual system is less effective in young plants.
Here’s a note that caught me by surprise.
Planta 148(3):217-21 (Apr 1980)
Pollen tube growth following compatible and incompatible intraspecific pollinations in Petunia hybrida.
Herrero M. Dickinson HG.
Abstract
The observation that both compatible and incompatible pollen tubes grow at identical speeds on the stigma in many plants with ‘gametophytically controlled’ self-incompatibility (SI) systems has, in Petunia, been extended to cover all other facets of pollen behaviour on this tissue. On entry into the stylar transmitting tissue both types of tubes accelerate, but the compatible achieve a higher terminal velocity than do the incompatible, which eventually slow and stop. Grafting experiments show that the top 1 mm of the stylar tissue can play an important rôle in determining the future development of the pollen tube. Following mixed pollinations, proportionally too many ‘compatible’ pollen tubes reach the ovary than would be expected from the results of ‘pure’ compatible and incompatible pollinations indicating that incompatible pollen in some way helps ‘prime’ the style for growth of compatible pollen tubes. This data is considered in terms of recent structural studies of these tissues, and related to the pollination conditions pertaining to Petunia populations in the field.
And some others:
http://bulbnrose.x10.mx/KKing/PollenNotes.html
Looking for something else, I came across an interesting article I’ve had on my web page for years.
Withers (1978) was primarily interested in lilies, but borrowed techniques derived from research into quite different plants.
http://bulbnrose.x10.mx/Heredity/WithersImprobab1978.html
Among other facts, he reported:
Mr R. R. Willing, working with poplars, eucalypts, petunias, and crosses between evergreen rhododendrons and deciduous azaleas, has found that both the pollen and the stigma have two components concerned with compatible and incompatible crosses.
In a compatible cross, the pollen germinates on the stigma, a pollen tube is produced, and fertilization and the production of viable seed follows.
In the incompatible cross, the pollen wall protein combines with a component of the stigma to form callose which obliterates the pollen tube and prevents fertilization. He has found that removal of one or other of these two factors prevents the formation of callose and makes the cross compatible.
He goes on to discuss how the factors can be removed, either by washing the pollen in a suitable solvent, or brushing the stigma(s) lightly with a solvent.
Successful fertilization is a complicated business. As I noted previously, incompatible pollen can improve the growth of compatible pollen tubes. Withers cites evidence that killed compatible pollen can favor the growth of incompatible pollen tubes.
Fun stuff!