So rapa and napus cross 50 - 100% ?
But oleracea needs juncea to cross at 10-50% ?
Those numbers are for hand pollination?
Read the article, my friend. I have saved it for my own reference so it was easy for me to link it but I wonāt pre-process it for you more than I already did 
On it.
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Here is a simpler one from a plant breeder. Surely a simplification compared to the pdf, but:
"But if you grow two brassicas of different species side by side, they will not cross.
(Yes, yes, there can be some chance crosses between species. But it is not common and for all intents and purposes they donāt cross.)
So if you have these 6 brassicas flowering in your garden at the same time:
Green Wave mustard (Brassica juncea)
Any arugula (Eruca sativa)
Vates green curly kale (Brassica oleracea)
Red russian Kale (Brassica napus)
Tokyo Bekana (Brassica rapa)
Some daikon radish (Raphanus sativus)
They will not cross with each other."
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Hehe, too fast having doubts.
When I asked some local farmers they would tell me not to plant the melons next to the pumpkins because otherwise the melons would not be sweet. 
And a lot of documents that I read were full of isolation distances and explanations to avoid crossings between varieties. 
If I interplant my seedling the crossing rate will be in between handcrossing and adjacent fields ācontaminationā from that paper. Much closer to handcrossing I assume. If I am not mistaken the brassicas are not self-fertile. The pollen probably will come from the near plants.
Brasica rapa 20 chromosomes can cross with brasica napus 38 chromosomes, at amazing rates of 50-100%. Less rating because I do not do hand pollination I do interplanting pollination. Maybe they cross with napus, or with the other rapas on the field. So they naturally cross in nature. A good place to start. So If I interplant them I should get some crosses.
I need to get some seeds from brassica juncea to cross with oleracea. Or just plant some mustard. So to hybridize oleracea 18 chromosomes I need to go to the route to juncea 36 chromosomes at a 10-50% rating for hand pollination. I will do interplantig pollination at a lesser rate. Or maybe I need to start hand pollination and make the crosses happening.
These two should naturally cross. And you get less seed from the plants?
Funny how we interpret the same document so differently
(no wonder there is so much conflict in this worldā¦ but thatās another chain of thoughtā¦)
My interpretation is that you can count with percentages much closer to ācontaminationā rates.
Yep, sometimes words have multiple meanings, intonation affects the meaning of the sentence, and then you add sarcastic meanings in the middle. You got a nice hieroglyphic going on.
I supose we do not have data about interplanting. Only data about hand crossing and information about adjacent fields. Maybe the full papers and references can add a bit more light, and have more information about the fields separation or distances.
Having so many factors that can affect the pollination, like the varieties themselves, is a bit out of scope of my modest mix.
Still nice to read and know more about it.
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You test and report back so we have a bit more data next time. not scientifically validated data, but still.
Iām about to create a certain turnip x radish cross and it hasnāt been easier to find info, ā¦if anything: even harder. Conclusive info, that is.
The main reason I think you get closer to ācontaminationā rates (with the possible exception of napus/rapa) is that in an interplanted setting, you have competing pollen from āown speciesā, let me call that āown pollenā, and by that I mean pollen from any napus in the same patch for the, say, napus mom. And then you have stray āforeign pollenā (say oleracea) that lands on a stigma that can very well have āownā pollen also.
Which pollen grain will then fertilize? I can see how foreign pollen can get there if thereās no own pollen, but I find it hard to imagine that the species would more readily accept pollen from another species as long as own pollen is also available.
When you emasculate and hand-pollinate, if you do it cleanly then thereās no stray own pollen which then means that you may get seed set from the foreign pollen only.
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Based on Carol Deppeās reports and my own experience, Iād say much closer to the hand pollination rate. She has a nice discussion in her book. Iāll summarize as the combination of not having blocks of thousands or millions of same-variety plants and having larger and more diverse pollinator populations.
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Oh, nice to know that. For me it did not make sense that the plant is waiting for an specific pollen, if the pollen is compatible will pollinate it, if not, it will wait for the correct pollen. The plant do not care about the variety or species, it will not wait for a better compatible pollen.
Most of the pollen comes from nearby plants right? Those number should be pretty low if we are talking about fields and not about nearby plants.
Most of those studies are skewed towards big mono crop fields, far from home grown gardens and polyculture.
It is not that the plant is waiting for ābetterā pollen. If different pollen grains are available simultaneously, some will germinate better and reach the ovary faster than others. Compatible pollen will simply outcompete moderately compatible pollen. With the possible exceoption of naopus/rapa which appear to be fully compatible, I would not expect much crossing between napus and oleracea from chance crosses.
Remember I got five (!!) seeds on oleracea from napus pollen, from pollinating approximately 120 flowers. Thatās a very, very low seed set when each flower has the potential to yield an entire pod with, I didnāt count but up to maybe 20 seeds. The reverse cross I didnāt count but I eyeball it to be maybe 150-200 seeds, from the same number of flowers, about 120. Much better, but my far not perfect seed set and that is from HP.
To post something encouraging (although perhaps irrelevant for your tests): all five crossed seeds germinated as of today!
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Nice, you will make them to bolt earlier to get more seeds?
Not sure yet whatās best. Last thing I want is to accudentally select for early bolting genetics. But to overwinter kale here is almost impossible. So if I want to build on/breed with them maybe I must do that (induce).
Took me a while to find the reference to a statement I made earlier here about how pollen grains will ācompeteā. Attaching it now.
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Haha, never mind it was the exact same reference Iād already uploaded earlier, we just missed the single most relevant part 
Shame on me! And you, too 
Those are such pretty plants! I can see why you want those, only even more frilly.
Hehe, I was thinking that you just shared for me to read completelly.
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