Hybrids are made much like with other crops...you emasculate a few flowers which are nearly ready to open by removing the anthers, then you spread pollen on them from the other parent.

Crossing blackberries and raspberries can be done, but the degree of success varies greatly, tending towards less than successful. Frequently the resulting plants are infertile and don't set fruit. This is often the result of odd ploidy numbers (for example, if you cross diploid (2x) raspberries with tetraploid (4x) blackberries, you'll get mostly triploid (3x) seedlings, which in most cases will be infertile.

In general, one is best matching ploidy levels, but for whatever reason, crosses between diploid blackberries and raspberries have a pretty bad track record. Tetraploid x tetraploid crosses have worked better, but tetraploid raspberries are rather uncommon.

Blackberries in your neck of the woods will likely be octoploid (8x), although eastern types are generally 4x. So a cross with a diploid raspberry would be (5x), which will probably be sterile. A tetraploid might work better (yielding 6x).

Tayberry is, I believe, hexaploid, being a cross between octoploid blackberry and a tetraploid raspberry. Silvan and Kotata are both hexaploid, too, although the crosses which originated them were hardly as simple...which leads me to my final point, which is that when dealing with a complex biological system, all sorts of seemingly inexplicable things can happen. For example, even though Silvan is 6x, it came from a cross of OSC742, which is 8x+3 (ie, octoploid plus three bonus chromosomes) and Marion, which is hexaploid.

Well, this has gotten long and unnecessarily complex. I've got a some background in Rubus breeding, so if you've got questions, I'm happy to help if I can.

I'd like to try a cross with Taybery x Kotata berry based on what you've said. Is there a good nursery source for unusual Rubus Hybrids in the US? I do also have the Baba Berry Raspberry, which I would like to cross with another Raspberry var.

I'm not familiar with any commercial source for anything too exotic. For researchers, there's always the USDA repository system, located in Corvallis, OR for blackberry and raspberry, but one has to be a "bonafide researcher" to get material from them. My impression has been that while major research institutions are taken care of first, if material is left some of the USDA repositories do make stuff available to serious hobbyists, if there is no reasonable means of obtaining it from elsewhere. It might be worth a try if you're looking for something unusual. I don't recall their website, but a Google search should turn it up...they've got complete lists of all the cultivars.

Tayberry x Kotata sounds like an interesting idea...I'd be interested to see how it turns out...I could see that yielding some nice fruit. All it takes is one good seedling.

How is Bababerry? I haven't personally seen it, but I've been thinking of trying to see if I could come up with a few raspberry hybrids that could make it here, (northern Florida), and Bababerry was suggested to me as something with decent heat tolerance. For the moment I'm sticking with the few blackberries I brought with me in pots, until I get time to track down a few raspberries.

I know a hybride called Veera or also the so called wyeberries. The best way is to pollinate diploid or tetraploid Raspberries with tetraploid blackberries. When you use diploid raspberries you normally have only up to 5 % fertile offspring, which can be also up to 20 % when using certain cultivars. NCGR Corvallis has for example two different tetraploid raspberries, also Prof. Harry Swartz has tetraploid raspberries as well.

I've asked for two assensions in the past from Corvallis and gotten two. My opinion is that as a hobbiest you should try to find a retail source first and only then approach Corvallis if you can't find it elsewhere.

The link to Corvallis is here:
http://www.ars-grin.gov/ars/PacWest/Corvallis/ncgr/

You should be able to search the database from here and request an assension.

Note, I neither tell them directly I'm not a researcher nor do I come across as just a backyard hobbiest.

In your case where they ask for the intended use, I would say that your wish to experiment on creating cross species hybrids in the genus Rubus.

Here is a link that might be useful: NATIONAL CLONAL GERMPLASM REPOSITORY

The people in the repository system just want to make sure the best use is being made of their limited resources (frequently they only have one or two plants of something, so the amount of cuttings/seed in one season is very limited)...I don't think they mind sending things to hobbyists if their main priorities (researchers, etc.) are taken care of. They just don't like to be used as a nursery for people to cheap and lazy to just order plants from commercial sources. But if you look at nurseries, you quickly start seeing the same two dozen (if that) cultivars over and over again...there's a lot more diversity out there than just that.

The clonal repositories are an amazing system, and if we don't use it then eventually it will likely go away. Particularly in small fruits, there's a lot more work that could be done than there are professional scientists to do it...it helps the whole community out if some of that work is done by hobbyists (provided they keep track of what they're doing well enough to learn something from it.)

Elazakal, do you know of any tetraploid raspberries?

I did get some Rubus Hawaiiensis seed from Corvalis and hopefully if the slugs don't get them, I'll have a few this fall. Have heard it is a very good sized berry. Plant looks like a cousin of Salmon berry.
Also grew out some seed of a superior wild Salmon Berry I found growing up by Port Hadlock WA. The parent plant was a good 10 feet tall and had very large orange fruit of good quality, "for a salmon berry, that is".

I am about 95% sure I have a Rubus Hawaiiensis seedling growing here in my garden. Ordered the Seed from NCGR Corvallis. It looks a lot like Salmon Berry, but there are a bit different char to it. May see a few berries in 2009. I suspect it is a diploid like Raspberry.
Have grown out a lot of Golden Raspberries from seed but so far, no evidence of any hybrids between Korean Wineberry and Raspberry here.

As I understand it all raspberry type fruits can crossbreed.
Luther Burbank even developed a "white blackberry " .
you can cross : raspberries, blackberries, thimble berries, wine berries, mulberries, dew berries, black caps,Tay berries , Logan berries , boysenberries, and most probably all others of that type . Seeing as you want want to make an improvement I believe the Northernmost and most cold tolerant plants are berries I believe of this family.Maybe you should breed them in to increase cold tolerance .
Fig. 1. Fruits and berries. a, Northern red currant (Ribes triste); b, c, Alpine bearberry
(Arctostaphylos alpina); d, Red bearberry (A. rubra); e, Bearberry (A. Uva-Ursi); f,
Mountain cranberry (Vaccinium VÂitis-ldaea) ; g, Bilberry ( V. uliginosum) ; h, Black crowberry
(Empetrum n i g m ) ; i, Baked-apple or cloud berry (Rabus Chmnaemorus). X 2/5.
berries. It grows in acid

We grow a type of berry we received from a renter whose Uncle developed he named newberries. He said it was a cross between wild blackberries and raspberries. they have a better taste with a little twang and look like a little longer raspberry, But can be pinched to form a bush and will not get any of the diseases