155-10-01: Roxburghii, are you in there??

For years there has been much discussion about the pedigree of a number of roses that list the species R. roxburghii as a parent. The Tantau Floribunda 'Floradora' (1944, Germany), for example, lists 'Baby Château' as the seed parent and R. roxburghii as the pollen parent.

Now, at a glance, there isn't the slightest hint of the species parent in the look of 'Floradora', which has led many to doubt its listed parentage. I myself doubted Tantau's pedigree for the longest time, at least unbtil I had some experience in using certain species and near-species hybrids in breeding, especially when they were employed as pollen parents. Let me elaborate.

I frequently use certain seed parents in making crosses that might be impossible on many other parents. After a while, you start to recognize which of your seed parents are likely to be "door openers" when planning iffy crosses. Introducing certain species can be especially difficult; sometimes the chromosome counts don't match, or the two varieties are simply too distant from one another in the family. I believe there are other unknown factors that play a role in fertility. Whatever the case, I found that even when using very willing seed parents, certain pollens would result in seed that, once germinated, turned out to be the result of apomixis*.

Apomixis is what happens when pollen initiates the fertilization response in a plant, but once the pollen tubes grow into the ovary, the genes prove unusable. So, in an effort to salvage the seed making process, the plant instead duplicates its own genes, in effect cloning itself. In roses, I suspect there is some recombinant action occurring as well, since some of the individuals arising from such crosses are not identical to the parent plant, but appear to be highly similar. In some cases undoubtedly some selfing may also occur, perhaps the result of insect activity, or simply incomplete emasculation.

The seedling you see pictured here was an experiment designed to see what happens when a (supposed) second generation R. roxburghii hybrid (in this instance, Moore's 0-47-19 was used) was crossed once again with the species R. roxburghii. And so, what we have here is:

[R. wichurana X ('Baby Château' X R. roxburghii)] X R. roxburghii normalis. Clearly, assuming the Tantau parentage is correct, we have a lot of species genes in this plant. Now, when I made this cross I expected one of three possible scenarios: total rejection of the pollen, apomixis, or self-pollination by insect vectors. As it happens, I got only a few hips from the 40 plus pollinations, leading me to believe they were likely the result if insect fiddling. From the approximately 20 seeds I sowed I got two seedlings. The one illustrated here is the healthier of the two; the other is far less vigorous, but it is trying to build up steam. (Maybe our cold, prolonged spring isn't to its liking; I know its not making me feel great!)

Until this individual reached a certain size I was unwilling to make many assumptions about its pedigree. But now, I look at it and I come to the conclusion that this is actually, for real, a R. roxburghii hybrid. Look closely: the most recent leaves are now composed of nine leaflets, surely a sign that roxburghii is influencing its development. I don't expect to see flowers this year, which is fine. Right now I am just fascinated to see its vegetative development. I doubt this is any kind of proof of the presence of R. roxburghii in its ancestor, 'Floradora', but it does show that when using the species, the resulting seedlings can show clear evidence of roxburghii traits. Fascinating.

*For more on apomixis, see the Wikipedia article here.

118-09-14

My apologies for posting an article about this same seedling twice; I wrote this last night, assuming I hadn't spoken about it before, but I did, last August. Still, its a different photo and I said some things here that I didn't the first time, so here we go....

118-09-14
Breeding: 42-03-02 X R. pisocarpa

The seed parent I used is one I am using more often as time goes by; a self seedling of Ralph Moore's Wichurana Rambler 0-47-19. (0-47-19 is a cross between R. wichurana and 'Floradora') My seedling 42-03-02 has been described in my blog before, but briefly, it is a dwarf-ish shrub to about 3 X 3 feet, with glossy small foliage and a constant supply of one inch deep pink to purple blooms in clusters of up to 30. It is extremely healthy and sets seed readily. It also happens to be a diploid.

In this case, the pollen parent I used is a particularly dark selection of R. pisocarpa that is growing near my home. At least 20 seedlings were selected from this cross in Summer 2010 and now reside in gallon cans. These were all extremely vigorous and quite healthy, but as expected, they have not flowered yet.....except the one shown here. This seedling, #14 began flowering sparingly in July, and bloomed twice more before cold weather shut it down for the year.

This is completely unexpected behavior, as none of these should be repeat blooming. Clearly this seedling shows R. pisocarpa influence, and in fact more closely resembles the species parent than it does the seed parent. Although rose genetics are, for the most part, quite straightforward, there are plenty of surprises to be found, especially when unconventional breeding lines are involved. (Yes, in this era I regard work with native species as "unconventional", although many of my peers - amateur hybridizers like myself - are often heavily invested in species work)

37-03-NE

Parentage: "0-47-19" (R. wichurana X 'Floradora') X 'Lilian Austin'. Possible triploid, but fully fertile. Repeats well, completely free of Blackspot, Mildew and Rust. It has a decent Apple-like scent. (Pardon this mediocre photo, it is apparently the only image I took of it)

This is a seedling that was planted out in the garden in 2005 and subsequently forgotten about: I had planted it in a section where other roses hid it from view for a while. I rediscovered it in the corner last Spring, tucked behind other roses and growing like a weed in spite of the fact that its irrigation had failed at least a year ago. I immediately set it to work as a seed bearer, noting that it was completely free of disease. I hope it may prove useful in my search for new lines of Blackspot immune roses. (R. wichurana is capable of breeding highly Blackspot resistant roses, we know that) Another trait R. wichurana often passes on to its progeny is ease of propagation by cuttings, and this seedling is no exception. I have a couple of band sized copies of this seedling which I am willing to share with other hybridizers. Contact me if you are seriously interested.

Transplanting tip #1

About working with R. wichurana hybrids.

One breeder I work with every year is Ralph Moore's 0-47-19, one of his most important hybrids used in the development of a number of his best roses. It is a cross of the species R. wichurana* and the old Floribunda from Tantau, 'Floradora'. ("Floradora' trivia: it now boasts 3466 descendants to its credit! Most of these come down to us through 0-47-19 and 'Queen Elizabeth')

I have found that there is a trick to raising seedlings from this first generation R. wichurana hybrid. They don't like to be transplanted from flats to pots at an early stage, or they tend to roll over and die. See that fairly large seedling in the upper right? Thats about the size these have to get before they can be transplanted successfully. So if you are working with R. wichurana or any of its first generation hybrids, you may want to let these get to at least the three leaf stage before transplanting them.

Oh, and one other thing: 0-47-19 has been my best hybrid for breeding Blackspot-free roses. I consider it a very important rose in the search for disease-proof roses. 0-47-19 was the seed parent for my 2009 repeat blooming Rambler 'Mel's Heritage', which is something like a repeat blooming 'Cecile Brunner', but more lax in habit.

*Yes, we are supposed to write the name as R. wichurana now and not the old spelling R. wichuraiana, which is now considered to be incorrect nomenclature. Classification systems grow and evolve and we have to adapt to these changes :-)