Self-Incompatibility

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jbergeson
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Re: Self-Incompatibility

Post: # 68145Post jbergeson
Tue Jul 24, 2018 7:32 pm

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.

Karl K
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Re: Self-Incompatibility

Post: # 68150Post Karl K
Wed Jul 25, 2018 3:52 pm

philip_la wrote:
Tue Jul 24, 2018 1:40 pm
"It is odd, though, that she found Rosa setigera to be strongly selfing."
A strongly selfing dioecious species? That's a pretty neat trick. Tends to make one question the other findings in that paper, however.
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/ ... a1990.html

Cole (1917), "R. setigera shows a large percentage of microsporic degeneracy."
http://bulbnrose.x10.mx/Roses/breeding/ ... ollen.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/ ... a1939.html

Karl K
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Re: Self-Incompatibility

Post: # 68164Post Karl K
Sun Jul 29, 2018 2:26 pm

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/Onli ... )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/WoodWa ... y1932.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.

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