Should we not remove the petals when pollinating?

Title: Two types of unfruitfulness found in artificial pollination experiments of apple

Authors: Komori, Sado; Soejima, Junichi; Tsuchiya, Shichiro; Masuda, Tetsuo; Bessho, Hideo; Ito, Yumi

Authors affiliation: Apple Res. Cent., Natl. Inst. Fruit Tree Sci., Shimokuriyagawa, Morioka, Iwate 020-01, Japan.

Published in: Journal of the Japanese Society for Horticultural Science, volumn 66, pages 289-295, (1997).

Abstract: “Two types of unfruitfulness were found in our apple breeding programs; one was in the reciprocal cross between ‘Kizashi’ and ‘Golden Delicious’ and the other in the crosses of HCR6T132, a strain bred in Purdue University, U. S. A., with pollen of other cultivars. The reciprocal cross between ‘Kizashi’ and ‘Golden Delicious’ resulted in very low rates of fruit set. Microscopic examinations revealed that pollen of both cultivars germinated normally on the stigma, but their tubes ceased growth in the upper part of the style; a number of pollen tubes formed swollen tips, indicating that the sterility was controlled by gametophytic incompatibility mechanisms. HCR6T132 yielded a high rate of fruit set when it was used as a pollen parent, whereas it failed as a seed parent. The unfruitfulness of the strain as a seed parent could not be ascribed to the incompatibility, because there was no difference in pollen tube behavior, compared with the cross compatible combinations. It was found that the fruit set was reduced when HCR6T132 flowers were emasculated (petals and anthers were removed) just before pollination; the injured flowers evolved much more ethylene than the intact ones. On intact flowers, the strains retains its fruitfulness, as did the treatment with AVG (aminoethoxyvinyl glycine), an ethylene synthesis inhibitor, to the emasculated flowers. These results revealed that the strain is probably very sensitive to ethylene and/or produces much wound ethylene, and that the unfruitfulness is ascribed to ethylene induced by emasculation.”

Wow, that’s something to think about.

Very interesting – maybe another approach would be to try and emasculate earlier, to allow the wounds to heal, and thus ethylene production to stop before it is time to pollinate.


I’ve been wondering recently about something that could relate to this. It seems to me that my roses will not uncommonly set hips in hot weather by themselves, whereas when emasculated and hand pollinated, absolutely will not. I’ve been wondering if perhaps it’s the increased humidity created around the stigma by the presence of the petals, but this is another possible explanation.

Jack Harkness found that seed set and germination in H. persica (R. persica), was much better when he didn’t emasculate the flowers.

White Pet has never set hips well for me. In April, I did 25 pollinations on it, 13 where I emasculated the flowers, and 12 where I didn’t emasculate them. I wasn’t worried about selfs because White Pet doesn’t set OP hips here. 1 of 13 emasculated flowers set hips, while 2 of 12 unemasculated flowers set hips. So hip set was twice as good with unemasculated flowers, but the sample size was too small to be statistically valid.

This is such a fascinating idea. Maybe we should use a light fabric with a tiny hole cut into it to only let the stigmas poke through (a la surgery in the operating room) for fertilizing.

Joyce Fleming’s idea of using Pellon (or any other type of light interfacing-even Stitch Witchery) would be perfect. Then we could fold the excess material over the top and it would protect the pollination and we could go back again and refertilize and the petals would hold everything together for a while. I love it ! Thanks, Henry !!

Hey, I thought the Pellon was my idea! I discovered a stack of it last year at a yard sale, and used it this year to cover the exogenous seeds, fixing it with a heat stapler. It works great, keeping the hot sun off the seeds while still allowing air circulation. It also dries very fast. I can’t say yet whether the covered exogenous seeds will germinate any better than the uncovered ones, but they sure are looking good so far. Haven’t lost any hips on the covered ones either.

Hmmm, it WOULD be a good idea to try it for pollinating to keep the sun off the stigmas.

I left the petals on last year with good success in germanations. I use the petals to protect the stigmas from the hot sun by using string or very small binder clips. In a small operation this is possible.

Maybe a spot of glue on the petals?

Dear Judith,

If the Pellon was your wonderful idea, please forgive my mistake. Thanks for writing about it. Linda

No problem, Linda, it’s entirely possible we both came up with it! :slight_smile:

Joseph, I found your thought quite intrigueing about emasculating sooner. I started emasculating the night before pollination (giving me about 24 hrs lead time) more from the standpoint of getting my collected pollen to release better and I’ve had greatly improved results with hip set since then. I wonder if part of that is related more to this concept than the pollen being “ready”. Very interesting…

Jerry, did you write about that method in an article once? I have been trying for the last couple of weeks to find an article that I remember reading about doing something like that…for some reason I was thinking it was an article by Winchel but perhaps it was actually something you wrote.