gemini x home run seedling oddities

I made a fair number of gemini x home run crosses this past year. The seeds have been germinating up a storm, BUT… I have seen a very high number of rootless seedlings AND a very high number of seedlings that look fine until about the 3rd trifoliate. After this they just stop growing. Ocassionally I have a normal seedling, but this is probably running about 1 out of 10-15. My take on this is that these 2 genomes just do not like one another.

Liz

I’ve got one cross like that Liz. The seedlings get to the third trifoliate and collapse.

I think they are just too genetically confused to live.

I have hope at least a few will survive. It’s heartbreaking to watch them fade after getting so far.

I had a similar situation happen last year. When the seeds opened up, instead of sending out a root first as usual they sent out the seed leaves and the roots never developed. I had a very low germination rate with them to begin with and coupled with the fact that so many didn’t develop roots meant I had very few seedlings survive. These were R.blanda OP seeds and most likely from more than one pollen parent, so it was was probably a problem with the seed parent more than with a particular cross.

Paul

I suspect there might be higher frequencies of oddities when we work with triploid parents (Home Run). During sex cell formation chromosome pairing and segregation can lead to aneuploid gametes- those with incomplete sets of chromosomes. Some get through if they are not too unbalanced and still are able to produce offspring. Aneuploid offspring can have severe problems. For instance, in a chromosome doubling study I did I found a seedling with 20 chromosomes and it grew slowly and had twisted, odd petioles. It probably was trying to stabilize at the triploid level or was close enough to it to survive, but was missing one chromosome and somehow that unbalance in gene dosage led to some challenges. In humans we know aneuploidy can have significant observable effects as well (extra chromosome 21 or duplicated region of 21 leads to Down’s Syndrome as one example).

When we use triploid parents, aneuploid gametes are more common and we may get a higher rate of weak seedlings than we would otherwise typically see. Perhaps one approach that can help is to use triploid pollen very heavily on stigmas of diploid or tetraploid females so pollen competition can help lead to more euploid gametes getting through due to frequently greater vigor and pollen competition.

Sincerely,

David

David, working with triploid banksia hybrids this is exactly what I’m observing. When using triploids in breeding one must grow out a larger than average number of offspring in order to select out those with normal vigor. This said there is still plenty to choose from. I suspect some resultant seedlings are making the jump to tetraploid as they are of normal vigor and apparently normal fertility.

Hybrids involving ‘Home Run’ as pollen parent are proving somewhat similar. It’s already apparent that some seedlings produced from tetraploid seed parent using ‘Home Run’ pollen are showing limited fertility as seed parent. I suspect these too will prove triploid.

Triploid x triploid crosses are the worst in terms of vigor but they are possible. I suspect if one were to grow out enough of them, those with average vigor could be obtained.

Yeah, I agree with your assessment David. This particular cross just really struck me as problematic. My Home Run seedlings from the 2006 crosses and Home Run seedlings from other 2007 crosses are not showing such a high frequency of off types. Perhaps Gemini is supporting more aneuploid pollinations to take than other seed parents???

Liz

Though genetic incompatibility may be the reason, it wouldn’t keep me from trying the cross one more time if it is an important one to you. I have seen some crosses one year fail miserably, then repeated the next year, do very well. Perhaps a mean fungus got in there and chewed up the newly forming root in the seed?!

Jim Sproul

Have you noted that some seed parents work really well one year and don’t the next?

Rose fertility vexes me at times.

I have Home Run still. I bought it asap the year before its big debut. However, I have still only tried it en mass with Cherry Meidiland. Im waiting on those to germinate. I still cannot decide any other crosses with it. I knew it would behave like First Prize in that one would have to use really bright or really dark roses to cross with it to get anything new in color. The fact that it is only decent as a male parent further hampers down the possibilities! I should probably cross it with Tatton, though. I got some nice coral and salmon shades out of Tatton x Rosarium Utersen last year. RU is also bland and monotoned like Home Run and First Prize. Another choice may be Tequlia, but I am waiting for germinations of that to see what kind of color patterns it produces. I think I crossed it with Ebb Tide last year? I forgot lol :stuck_out_tongue:

Home Run works on nearly everything, gives mostly red singles for me and some pinks so far. Some offspring act like triploids. I would think it would be great on Cherry Mediland.

Like my use with ‘Baby Love’, I hit ‘Home Run’ hard the first year, but used mainly its seedlings last year in crosses. I think that both (BL and HR) are very strong in single form and you need to move a generation or more away to get more exciting possibilities.

Jim Sproul

My Home Run seems to be setting fruit for the first time this year. Some are close to ripe. I don’t want to open them up will I am sure the seed are mature.

I will probably sow them for fun.

I would have bet I wouldn’t find hips on this one ever. Weird!